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Tektronix 545 -170 v on -150 volt line
10/26/2009 1:21:56 PMDave Froehlich
Hello All,
I've decided to measure voltages. The first voltage measurement is the -150v because it's the most important. I measure -170 volts and cannot adjust it down to -150 volts. What could be at fault? I have unplugged the 6080 so the resistor R756 cannot overheat. How do I test the 5651. My tube tester has no settings for such a tube. Is there one of the 0 tubes that's similar?

Thanks,

Dave

10/26/2009 1:50:30 PMWarren
http://www.nj7p.org/Tube4.php?tube=5651

Click on "same base" there are 0A2 0B2 0C2

10/26/2009 2:41:34 PMDave Froehlich
Warren,
OA2, 0B2 and 0C2 tube tester settings would destroy the 5651. So I don't think I will test it.
One of the 12B4s V794 fails the mutual conductance test. This is the one in the 500 volt line. It passes on the emission test though.

Thanks,

Dave
:http://www.nj7p.org/Tube4.php?tube=5651
:
:Click on "same base" there are 0A2 0B2 0C2
:

10/26/2009 2:29:11 PMRadiodoc
Dave,

If the tube glows, it is likely that it is ok. Between pins 2, 7 or 4 and pins 1 or 5 you should measure around 83 to 88 VDC. May have to wait 3 or so minutes of operation for voltage to settle down.

Radiodoc
*******************


:Hello All,
: I've decided to measure voltages. The first voltage measurement is the -150v because it's the most important. I measure -170 volts and cannot adjust it down to -150 volts. What could be at fault? I have unplugged the 6080 so the resistor R756 cannot overheat. How do I test the 5651. My tube tester has no settings for such a tube. Is there one of the 0 tubes that's similar?
:
:Thanks,
:
:Dave
:

10/26/2009 2:43:01 PMDave Froehlich
Radiodoc,
The tube does glow fine right after the relay energizes.

Thanks,

Dave
:Dave,
:
:If the tube glows, it is likely that it is ok. Between pins 2, 7 or 4 and pins 1 or 5 you should measure around 83 to 88 VDC. May have to wait 3 or so minutes of operation for voltage to settle down.
:
:Radiodoc
:*******************
:
:
::Hello All,
:: I've decided to measure voltages. The first voltage measurement is the -150v because it's the most important. I measure -170 volts and cannot adjust it down to -150 volts. What could be at fault? I have unplugged the 6080 so the resistor R756 cannot overheat. How do I test the 5651. My tube tester has no settings for such a tube. Is there one of the 0 tubes that's similar?
::
::Thanks,
::
::Dave
::
:

10/27/2009 6:11:04 AMEdd






Sir David. . . .

Well here we are again exploring yet another branch on the total repair aspect. Wayyy back
on day one, was not my first few "breaths " from my keyboard being relevant to the confirmantion
of the presence and tolerances of ALL of the LVPS's developed supply voltages?


That, even being with a very detailed explanation of all of the supply voltages, and the
dependent fact that almost all were "electrically interlocked" to each other

That which you are running up against now is the fact that the hoz positioning, is
related to a capability of needing a completely seamless shift of a DC voltage. Now that
might be dependent, at one point, of a swing down from being a +DC voltage and down to
a zero voltage axis and then a swing onto a transitional shift into being a - voltage
level.


Remember, this scope extensively uses DC coupled differential stages which are dependent upon
use of bipolar supplies.


Alas, your -150 supply is a bit higher than its prescribed level so that is upsetting other conditons, since it is used in so many other portions of the set.


ADJUNCT ASIDE:



I don't remember the units hoz positioning control, being other than the common dual
concentric control, that is using a high value pot along with a smaller pot such that the combo
gives a coarse and vernier adjustment capability.


You then just place the start of trace, at the very left graticule indexing of the grid display matrix.


Now you ALSO have a Helipot control on the front panel in the form of the vernier delay adjustment
of the B mode time delay onset, if using the "B" delayed sweep functions capability of the unit.


It would NOT be relevant to you at all, until you get this unit percolating, you will be placing
the HOZ sweep option switch at its very top, upper,center "A" sweep mode option.



Let me now go into a detail of the basic operation principle of the - 150 supply.



Seems like that I tacked the LVPS Supply Working Schematic on to many different points, but
this one seems to kick right in . . .unless on rural- party line - hand crank- dial up . . . .meet
you here, same time on Thursday !


Seek out:

http://www.nostalgiaair.org/Forums/Messages/530/M0080530.htm




Looking at the -150 supply portion, and reiterating again, the - supply line is a direct
connection from - line of the DC raw supply, with no inline obstructions, with it then emerging
at the far right, as being the designated -150 supply terminus.


And NOW, the positive portion of the raw DC supply, is then feeding on over to the plates of
a triad bank of (3) 12B4 power reg tubes.


The basic regulation concept of this stage is dependent upon that trio of tubes experiencing
an initial turn on with their 1st grids conduction biasing being acquired via that R729 which
you see going up to its supply source . . .the +110 regulated supply source, so
now I ask you . . . . GOT MILK ? . .errrr make that +100 VDC supply voltage ?


As it stands, if that bias voltage is present and is unhampered, the 12B4 trio would be driven
into so full of a degree of conduction, that there would only be the voltage drop across the
plate-cathode of the tubes that is making a path to ground via the cathodes.


In that conditon, the supply would be having a MUCH-MUCH greater output voltage than the desired
-150 VDC benchmark.
( . .BTW . . .Now, isn't that the EXACT condition which you are now experiencing ?)


Soooooo go back to the schema and notice the daisy chaining of all of the 12B4 1st grids, along with
their final emergence being over to the left and downwards to the plate of the V700 comparator stage
where,in actuality, it is then providing that stages plate supply voltage also.


Then, there is a straight forward technique in the screen voltage acquisition for that V700 stage.


When looking at its 1st grid control voltage, we see it as being routed in from a tap off
of a resistive voltage divider(R707-706) that is going over to connect across the plate of a DC
differential pair- DC coupled amplifier stage.


That same plate is receiving ITS supply voltage via the R719 resistor from the + 100 VDC supply.


The idea now in the regulation aspect, is for that 12B4 trio to not FULLY conduct, but to only
partially conduct, such that they can be responsible for creating the voltage drop which decreases that initial FULL raw DC supply, on down to the required -150 volt level.



That is being accomplished by two conditions, initially by the aquisition of a stable voltage reference source to input at the 1st grid of the left triode of that V712 differential DC amp stage.


Notice the presence of the 5651 gas tube regulator, being placed between the negative supply buss and a current limiting resistor R710, a complete series power loop is then made by the final connection of the other electrode of the 5651 to ground.


There is then the series resistor isolation that is provided by resistor R711 and the final presence of a slightly dropped initial ~87 voltage level that was developed across the conducting 5651 gaseous regulator reference.


The next aspect then would be the right half triode of V712 where its plate is receiving its supply from the R719 resistor.


Look now at the R718-R716-R715 voltage divider trio, with their interrelated RATIO of values, being chosen such that a min and max of adjustment range limits could be acquired.


That sampling across the -105 VDC output voltage , is fed on in thru isolative resistor R717 and then
presents a sampled volage to the 1st grid of the right triode of the diferential pair.


Note that the pair of triodes cathodes are tied together and then sharing a common cathode resistor.
Look and see the fixed voltage reference over at the left triodes first grid.


Also see the voltage dividers sample of the level of voltage present across the -150VDC
supply that is feeding into the right triodes 1st grid.


With that DC level sharing of the stages, that voltage level present at the #6 plate of the right triode will walk up and down in value, with any shift of that -150 supply buss level.


A portion of that difference is tapped off via the R707-R706 resistive voltage divider to then feed
in as a controlling and corrective grid bias, to the 1st grid of the V700 comparator stage.


If there is a need for a voltage correction, from there being too high of a voltage presence at the
-150 VDC buss sampling, the slight presence of a more positive voltage to the 1st grid of V700 then
increases its conduction.


More conduction in that V700 stage then means that the common V700 plate to 1st grid connection to
the 12B4 trio is going to pull down on, and bleed down that grid turn on + level that is continually
being provided via R729 from the +100 V supply.


The end result is the soaking up of the excess voltage via the 12B4 cluster and the regulation of the output buss down to the prescribed -150VDC.




Regulation Technique Summation:




The left V712 triode's 1st grid receives a sample of the stable voltage reference.

The right V712 triode's 1st grid receives a sample of a segment of of -105 V supply buss level.

They compare . . . and any variance from the norm will result in a shifting up or down of the plate

supply voltage of the right triode of V712.

That potentially variant voltage then feeds over to the 1st grid of the V700 comparator stage, its
potentially variant grid biasing swing could then provide for more or less conduction in accordance
as to whether it was making a + swing or a - swing.


That varying degree of conduction at the plate of V700 IS ALSO directly tied into the 1st grids of the 12B4 triodes.




Net Result . . . . would then be:




If V700 conducts more heavily, it pulls down the normal + grid bias present on those 12B4 stages via the R729 supply resistor from the +100VDC supply.


As they conduct less, that trio starts absorbing more of the surplus voltage presence, thus the -105 buss has a reduced voltage level presence, with it then shifting down to the specified -105 level.


Same control effect on the other situation of the -105 supply output being at LESS that its desired output voltage level.
In that situation the V700 would be needing to conduct LESS in order for there to be less pull down of the static + bias being fed into the 12B4's 1st grids.




How to do-it-to-it:




DVM probe to chassis ground, and then you use its other probe to 2-4 or 7 of the 5651 . . if you then find an ~87 V presence, the gas tube is firing and regulating as it should .




Move metering to the center terminal of R716 pot [ -150 supply adjust ] and swing the pot thru its range, to confirm an according voltage swing on the meter. . .if so.




Move metering to the Pin #6 plate of V712, keep up the same swinging of the R716 thru its range to see if there is a like variable response in the swinging of that plate level.. . .if so.




Move metering to the Pin #1 1 st grid of the V700 comparator stage plate to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.



Move metering to the Pin #7 of V725 1st grid to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.



NOW, you MOVE metering over to being across Pin #1 and pin #9 of V725 to see what the maximum voltage developed is, at the setting of the -150 adjustment pot which results in the highest voltage reading.


If that is not high enough, that is why your raw B+ level is not being able to be adjusted down to that -105 standard level.


Go back and check the screen, plate, first grid and cathode voltages of the V700 and check for their variance from the schematics estimation of those voltages.





ZUJ'ing





73's de Edd










10/27/2009 11:44:27 AMJoe Wutsch
:
:

:
:
:
:Hey,
I just dug my 545A out and will start working on it.
The last time I had it out I was going to replace the diodes in the HV section with semiconductor replacements and put a resistor on each of the filaments. My big question is do you have to use Silver solder in the HV section only and the rest of the unit 60/40?

Thanks,
Joe


:
:
:Sir David. . . .
:
:
:
:Well here we are again exploring yet another branch on the total repair aspect. Wayyy back
:on day one, was not my first few "breaths " from my keyboard being relevant to the confirmantion
:of the presence and tolerances of ALL of the LVPS's developed supply voltages?
:
:
:
:
:That, even being with a very detailed explanation of all of the supply voltages, and the
:dependent fact that almost all were "electrically interlocked" to each other
:
:
:
:That which you are running up against now is the fact that the hoz positioning, is
:related to a capability of needing a completely seamless shift of a DC voltage. Now that
:might be dependent, at one point, of a swing down from being a +DC voltage and down to
:a zero voltage axis and then a swing onto a transitional shift into being a - voltage
:level.
:
:
:Remember, this scope extensively uses DC coupled differential stages which are dependent upon
:use of bipolar supplies.
:
:
:Alas, your -150 supply is a bit higher than its prescribed level so that is upsetting other conditons, since it is used in so many other portions of the set.
:
:
:
:
:ADJUNCT ASIDE:
:
:
:
:I don't remember the units hoz positioning control, being other than the common dual
:concentric control, that is using a high value pot along with a smaller pot such that the combo
:gives a coarse and vernier adjustment capability.
:
:
:You then just place the start of trace, at the very left graticule indexing of the grid display matrix.
:
:
:
:
:Now you ALSO have a Helipot control on the front panel in the form of the vernier delay adjustment
:of the B mode time delay onset, if using the "B" delayed sweep functions capability of the unit.
:
:
:It would NOT be relevant to you at all, until you get this unit percolating, you will be placing
:the HOZ sweep option switch at its very top, upper,center "A" sweep mode option.
:
:
:
:
:Let me now go into a detail of the basic operation principle of the - 150 supply.
:
:
:
:Seems like that I tacked the LVPS Supply Working Schematic on to many different points, but
:this one seems to kick right in . . .unless on rural- party line - hand crank- dial up . . . .meet
:you here, same time on Thursday !
:
:
:Seek out:
:
:http://www.nostalgiaair.org/Forums/Messages/530/M0080530.htm
:
:
:
:
:Looking at the -150 supply portion, and reiterating again, the - supply line is a direct
:connection from - line of the DC raw supply, with no inline obstructions, with it then emerging
:at the far right, as being the designated -150 supply terminus.
:
:
:And NOW, the positive portion of the raw DC supply, is then feeding on over to the plates of
:a triad bank of (3) 12B4 power reg tubes.
:
:
:
:
:The basic regulation concept of this stage is dependent upon that trio of tubes experiencing
:an initial turn on with their 1st grids conduction biasing being acquired via that R729 which
:you see going up to its supply source . . .the +110 regulated supply source, so
:now I ask you . . . . GOT MILK ? . .errrr make that +100 VDC supply voltage ?
:
:
:As it stands, if that bias voltage is present and is unhampered, the 12B4 trio would be driven
:into so full of a degree of conduction, that there would only be the voltage drop across the
:plate-cathode of the tubes that is making a path to ground via the cathodes.
:
:
:In that conditon, the supply would be having a MUCH-MUCH greater output voltage than the desired
:-150 VDC benchmark.
:( . .BTW . . .Now, isn't that the EXACT condition which you are now experiencing ?)
:
:
:Soooooo go back to the schema and notice the daisy chaining of all of the 12B4 1st grids, along with
:their final emergence being over to the left and downwards to the plate of the V700 comparator stage
:where,in actuality, it is then providing that stages plate supply voltage also.
:
:
:Then, there is a straight forward technique in the screen voltage acquisition for that V700 stage.
:
:
:When looking at its 1st grid control voltage, we see it as being routed in from a tap off
:of a resistive voltage divider(R707-706) that is going over to connect across the plate of a DC
:differential pair- DC coupled amplifier stage.
:
:
:That same plate is receiving ITS supply voltage via the R719 resistor from the + 100 VDC supply.
:
:
:The idea now in the regulation aspect, is for that 12B4 trio to not FULLY conduct, but to only
:partially conduct, such that they can be responsible for creating the voltage drop which decreases that initial FULL raw DC supply, on down to the required -150 volt level.
:
:
:
:That is being accomplished by two conditions, initially by the aquisition of a stable voltage reference source to input at the 1st grid of the left triode of that V712 differential DC amp stage.
:
:
:Notice the presence of the 5651 gas tube regulator, being placed between the negative supply buss and a current limiting resistor R710, a complete series power loop is then made by the final connection of the other electrode of the 5651 to ground.
:
:
:There is then the series resistor isolation that is provided by resistor R711 and the final presence of a slightly dropped initial ~87 voltage level that was developed across the conducting 5651 gaseous regulator reference.
:
:
:The next aspect then would be the right half triode of V712 where its plate is receiving its supply from the R719 resistor.
:
:
:Look now at the R718-R716-R715 voltage divider trio, with their interrelated RATIO of values, being chosen such that a min and max of adjustment range limits could be acquired.
:
:
:That sampling across the -105 VDC output voltage , is fed on in thru isolative resistor R717 and then
:presents a sampled volage to the 1st grid of the right triode of the diferential pair.
:
:
:Note that the pair of triodes cathodes are tied together and then sharing a common cathode resistor.
:Look and see the fixed voltage reference over at the left triodes first grid.
:
:
:Also see the voltage dividers sample of the level of voltage present across the -150VDC
:supply that is feeding into the right triodes 1st grid.
:
:
:With that DC level sharing of the stages, that voltage level present at the #6 plate of the right triode will walk up and down in value, with any shift of that -150 supply buss level.
:
:
:A portion of that difference is tapped off via the R707-R706 resistive voltage divider to then feed
:in as a controlling and corrective grid bias, to the 1st grid of the V700 comparator stage.
:
:
:If there is a need for a voltage correction, from there being too high of a voltage presence at the
:-150 VDC buss sampling, the slight presence of a more positive voltage to the 1st grid of V700 then
:increases its conduction.
:
:
:More conduction in that V700 stage then means that the common V700 plate to 1st grid connection to
:the 12B4 trio is going to pull down on, and bleed down that grid turn on + level that is continually
:being provided via R729 from the +100 V supply.
:
:
:The end result is the soaking up of the excess voltage via the 12B4 cluster and the regulation of the output buss down to the prescribed -150VDC.
:
:
:
:
: Regulation Technique Summation:
:
:
:
:
:The left V712 triode's 1st grid receives a sample of the stable voltage reference.
:
:
:
:The right V712 triode's 1st grid receives a sample of a segment of of -105 V supply buss level.
:
:
:
:They compare . . . and any variance from the norm will result in a shifting up or down of the plate
:
:supply voltage of the right triode of V712.
:
:
:
:That potentially variant voltage then feeds over to the 1st grid of the V700 comparator stage, its
:potentially variant grid biasing swing could then provide for more or less conduction in accordance
:as to whether it was making a + swing or a - swing.
:
:
:That varying degree of conduction at the plate of V700 IS ALSO directly tied into the 1st grids of the 12B4 triodes.
:
:
:
:
:Net Result . . . . would then be:
:
:
:
:
:If V700 conducts more heavily, it pulls down the normal + grid bias present on those 12B4 stages via the R729 supply resistor from the +100VDC supply.
:
:
:As they conduct less, that trio starts absorbing more of the surplus voltage presence, thus the -105 buss has a reduced voltage level presence, with it then shifting down to the specified -105 level.
:
:
:Same control effect on the other situation of the -105 supply output being at LESS that its desired output voltage level.
:In that situation the V700 would be needing to conduct LESS in order for there to be less pull down of the static + bias being fed into the 12B4's 1st grids.
:
:
:
:
:How to do-it-to-it:
:
:
:
:
:DVM probe to chassis ground, and then you use its other probe to 2-4 or 7 of the 5651 . . if you then find an ~87 V presence, the gas tube is firing and regulating as it should .
:
:
:
:
:Move metering to the center terminal of R716 pot [ -150 supply adjust ] and swing the pot thru its range, to confirm an according voltage swing on the meter. . .if so.
:
:
:
:
:Move metering to the Pin #6 plate of V712, keep up the same swinging of the R716 thru its range to see if there is a like variable response in the swinging of that plate level.. . .if so.
:
:
:
:
:Move metering to the Pin #1 1 st grid of the V700 comparator stage plate to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:
:
:
:
:
:Move metering to the Pin #7 of V725 1st grid to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:
:
:
:
:
:NOW, you MOVE metering over to being across Pin #1 and pin #9 of V725 to see what the maximum voltage developed is, at the setting of the -150 adjustment pot which results in the highest voltage reading.
:
:
:If that is not high enough, that is why your raw B+ level is not being able to be adjusted down to that -105 standard level.
:
:
:Go back and check the screen, plate, first grid and cathode voltages of the V700 and check for their variance from the schematics estimation of those voltages.
:
:
:
:
:
:ZUJ'ing
:
:
:
:
:
:
:
:73's de Edd
:
:
:


:

:
:
:
:
:
:
:
10/27/2009 3:13:12 PMEdd







Sir Joe. . .



Me thinks that the situation on the solder, was the simple consideration that if one . . .John Doe . . .Eng or Tekkie
extra-ordinaire . . . . who wasn't working right in the instrumentation / calibration / repair field of expertise,
would have a problem locating that solder , so they included some multiple loops of it within the instrument.
Also might I clarify its somewhat misleading referencing to it as being "silver" solder.


Which is a "hard" type of compilation of completely different metals , which requires "heat city" in getting it
into its initial plastic state and then even more to get it on into the flowing and fusing state.


The proper wording for the solder type we are referring to would be that of "silver bearing solder".




The mentioned solder, being a slight variant of the electronics servicing blend of 60%tin / 40% lead or the
upgrading to SUPER blend of the eutectic grade by the skewing of that blend to ~ 63%tin / 37% lead
eutectic blend, where there is then the advantage of flowing into / out of a liquid/solid state with the absolute
shortest transitional time.

( Benefit . . . .less chance of a cold / fractured joint problem if subjected to a
micro-movement during soldering cool down.)


And then there is the mentioned silver bearing solder category which shifts the blend to potentially having
up to a 5% silver content. That enhances conductivity, corrosion resistance and enhances "wettability".


And now, as for the final " Cow-Pee-'De-Grass " on the pertinent info , would be the exacting reasoning on the
desirability of using silver bearing solder on a units repair.


I strongly believe that would PRINCIPALLY be directed towards soldering repairs involving their NEAT little,
what I call . . .ceramic terminal "troughs" . . .which they came up with and started using in their construction
of instrumentation. Probably being used in instruments up to the point where PCB construction then became
the norm. With their possible retention in hard wiring sites that were not feasible to be incorporated on a PCB.




. . . . . . Example of a TEK type of terminal strip.



I don't currently have a strip on hand to mechanically and microscopically examine, but there are the separate
silver troughs which are located within cutouts within the ceramic form. Anyone correct me if wrong, but it
seems that waaaaay back in first generation they actually had silver OR copper, with silver plating that fit down
within those slots within the ceramic. Seems like I had seen both the incorporation of both the flat looking bisque
form of ceramic used and then some units having received a glaze and a firing to end up as being Hard----Shiny
City as their end result.

Assuredly those units would lean towards being used in Hi Voltage environs or in an area
you would not want a solid condensation conductivity path from humidity on them.


Now it seems that at point in time that they reverted to different type of construction, where they tried to simplify /
automate the construction of the troughs .


So it seems like that they might have taken a page from the potentiometer manufacturers where they would have
the need of placing a conductive path on a ceramic blank, but could not get away with the mere use of a graphite slurry to perform condudction, as the pot manufacturers might have used. But the pot manufacturers also ran into particular
situatons where they needed to solder a wire to a connection which was interfacing with circuitrty on a ceramic blank.
I can remenber that in three different manners / stages of development.



Technique #1:


Initially there was the mechanical technique of having the "contact area" portion of the ceramic just being mechanically
abraded with a coarse silicon carbide wheel , leaving a porous and somewhat rough surfacing in that area.


( This being akin to the liberal roughing up of the somewhat shiny and glazed surfacing of an inner tube , before the then
additon of rubber cement /vulcanizing agent , and the final pressing on of a patch.)


If one then takes a spinning disk of soft copper and make a gradual pressing into the abraded surface, one can see it fill in
the porous cavities and then start building up a smooth surface of copper.


If one then has a build up of copper, and does not solder like an amateur, and facilitates by the use of flux, one then can
build up a surfactally tinned contact area.


It is then a piece of cake to take your connecting wire lead, strip it, pre tin it and then move over and reflow solder onto
the pretinned contact area.


Now just who said that you couldn't solder to ceramic . . . .or even GLASS for that matter.


Oh, this just gets easier, since with silver , it is so soft and malleable, in comparison to that use of copper, that it really
is much easier to use and permits an even more impressive ease of application and overall build up capability.


Now . . . .ya wanna see me solder to ceramic ?


That is the primary manner of interfacing connections to ceramic, that I remembered being utilized, but there was also:




Technique #1:
A variant similar to the "baby shoe bronzing" technique of placing a graphite coating on a nonconductor (leather baby
shoe) /or /ceramic ? and then electroplating copper on the surface to an adequate build up level. Or in the case of the
use of ceramic for making a connection terminus, the then placing of a silverplate onto the copper.




Technique #3:
Modern day technology, in the respect of having the contact area(s) of interest, being the only ones openly exposed,
with all of the other area masked off. The ceramic unit is then placed in a vacuum bell and within, there is sacrificial
silver that has a very high voltage and current arc developed across it. A full vacuum is then pulled within the bell
the silver is the arced and totally vaporizes, a thin film of silver is deposited down within the porously abraded contact
area. Multiple operations then build up the thicknesses of the deposited silver.




I don't know the evolution of the maufacture of the Tek terminal "trough" strip, but would guess that the day one
consideration of a silver insert into a ceramic block and its economic variants of using less silver content and
eventually silver plate. And then, the sheer volume of quantity used and the need of a speedier as well as more
economical manufacturing mode might have led to a variant of the interfacing to ceramic as was used by the
potentiometer / control manufacturers.


At least in the controls situation, they can have a terminal area and then a degree of termal isolation where a
deposition of a slurry of graphite could interface between that terminal and a resistive contact strip of the control.


Even back at the manufacturing point of having a contact divot swaged or imbedded into a bisque ceramic block
and then fired, that might seem to be the necessary technique to make a solid mechanical interfacing and yet
hold up to some of the errant degree of overheating that it might be subjected to by SOME repair persons.


I have never quite found a family of epoxy which would hold up to extended soldering iron heat levels, other
than fast reflow operations. (Even the industrial E-pon and Hy-Sol families.)


Keep the soldering heat on too long on an epoxy anchored terminal and the bubbles will flow out from it.




Soooooo this all resulted in a full technical fill in . .why for . . as to the query about the use of silver bearing
solder on repairs, with my thinking that the full consideration might precisely be just related to those terminal
"troughs" in the aspect of placing soldering iron heat on those terminal "troughs" and then the pulling out of
solder clad leads of associative components from them and placing in new component leads.


THEN, if you should be using a common solder, to then flow a great new anount of it down to fill in the "trough"
the potential is there for that plain solder to leech out . .and carry away . . .some of that silver which is interfacing
in the bonding to the ceramic substrate, thus weakening its bond integrity.


The use of a silver bearing solder would profusely abate that proclivity.


Thassit . . . . .




73's de Edd






::
::

::
::
::
::Hey,
:I just dug my 545A out and will start working on it.
:The last time I had it out I was going to replace the diodes in the HV section with semiconductor replacements and put a resistor on each of the filaments. My big question is do you have to use Silver solder in the HV section only and the rest of the unit 60/40?
:
:Thanks,
:Joe
:
:
::
::
::Sir David. . . .
::
::
::
::Well here we are again exploring yet another branch on the total repair aspect. Wayyy back
::on day one, was not my first few "breaths " from my keyboard being relevant to the confirmantion
::of the presence and tolerances of ALL of the LVPS's developed supply voltages?
::
::
::
::
::That, even being with a very detailed explanation of all of the supply voltages, and the
::dependent fact that almost all were "electrically interlocked" to each other
::
::
::
::That which you are running up against now is the fact that the hoz positioning, is
::related to a capability of needing a completely seamless shift of a DC voltage. Now that
::might be dependent, at one point, of a swing down from being a +DC voltage and down to
::a zero voltage axis and then a swing onto a transitional shift into being a - voltage
::level.
::
::
::Remember, this scope extensively uses DC coupled differential stages which are dependent upon
::use of bipolar supplies.
::
::
::Alas, your -150 supply is a bit higher than its prescribed level so that is upsetting other conditons, since it is used in so many other portions of the set.
::
::
::
::
::ADJUNCT ASIDE:
::
::
::
::I don't remember the units hoz positioning control, being other than the common dual
::concentric control, that is using a high value pot along with a smaller pot such that the combo
::gives a coarse and vernier adjustment capability.
::
::
::You then just place the start of trace, at the very left graticule indexing of the grid display matrix.
::
::
::
::
::Now you ALSO have a Helipot control on the front panel in the form of the vernier delay adjustment
::of the B mode time delay onset, if using the "B" delayed sweep functions capability of the unit.
::
::
::It would NOT be relevant to you at all, until you get this unit percolating, you will be placing
::the HOZ sweep option switch at its very top, upper,center "A" sweep mode option.
::
::
::
::
::Let me now go into a detail of the basic operation principle of the - 150 supply.
::
::
::
::Seems like that I tacked the LVPS Supply Working Schematic on to many different points, but
::this one seems to kick right in . . .unless on rural- party line - hand crank- dial up . . . .meet
::you here, same time on Thursday !
::
::
::Seek out:
::
::http://www.nostalgiaair.org/Forums/Messages/530/M0080530.htm
::
::
::
::
::Looking at the -150 supply portion, and reiterating again, the - supply line is a direct
::connection from - line of the DC raw supply, with no inline obstructions, with it then emerging
::at the far right, as being the designated -150 supply terminus.
::
::
::And NOW, the positive portion of the raw DC supply, is then feeding on over to the plates of
::a triad bank of (3) 12B4 power reg tubes.
::
::
::
::
::The basic regulation concept of this stage is dependent upon that trio of tubes experiencing
::an initial turn on with their 1st grids conduction biasing being acquired via that R729 which
::you see going up to its supply source . . .the +110 regulated supply source, so
::now I ask you . . . . GOT MILK ? . .errrr make that +100 VDC supply voltage ?
::
::
::As it stands, if that bias voltage is present and is unhampered, the 12B4 trio would be driven
::into so full of a degree of conduction, that there would only be the voltage drop across the
::plate-cathode of the tubes that is making a path to ground via the cathodes.
::
::
::In that conditon, the supply would be having a MUCH-MUCH greater output voltage than the desired
::-150 VDC benchmark.
::( . .BTW . . .Now, isn't that the EXACT condition which you are now experiencing ?)
::
::
::Soooooo go back to the schema and notice the daisy chaining of all of the 12B4 1st grids, along with
::their final emergence being over to the left and downwards to the plate of the V700 comparator stage
::where,in actuality, it is then providing that stages plate supply voltage also.
::
::
::Then, there is a straight forward technique in the screen voltage acquisition for that V700 stage.
::
::
::When looking at its 1st grid control voltage, we see it as being routed in from a tap off
::of a resistive voltage divider(R707-706) that is going over to connect across the plate of a DC
::differential pair- DC coupled amplifier stage.
::
::
::That same plate is receiving ITS supply voltage via the R719 resistor from the + 100 VDC supply.
::
::
::The idea now in the regulation aspect, is for that 12B4 trio to not FULLY conduct, but to only
::partially conduct, such that they can be responsible for creating the voltage drop which decreases that initial FULL raw DC supply, on down to the required -150 volt level.
::
::
::
::That is being accomplished by two conditions, initially by the aquisition of a stable voltage reference source to input at the 1st grid of the left triode of that V712 differential DC amp stage.
::
::
::Notice the presence of the 5651 gas tube regulator, being placed between the negative supply buss and a current limiting resistor R710, a complete series power loop is then made by the final connection of the other electrode of the 5651 to ground.
::
::
::There is then the series resistor isolation that is provided by resistor R711 and the final presence of a slightly dropped initial ~87 voltage level that was developed across the conducting 5651 gaseous regulator reference.
::
::
::The next aspect then would be the right half triode of V712 where its plate is receiving its supply from the R719 resistor.
::
::
::Look now at the R718-R716-R715 voltage divider trio, with their interrelated RATIO of values, being chosen such that a min and max of adjustment range limits could be acquired.
::
::
::That sampling across the -105 VDC output voltage , is fed on in thru isolative resistor R717 and then
::presents a sampled volage to the 1st grid of the right triode of the diferential pair.
::
::
::Note that the pair of triodes cathodes are tied together and then sharing a common cathode resistor.
::Look and see the fixed voltage reference over at the left triodes first grid.
::
::
::Also see the voltage dividers sample of the level of voltage present across the -150VDC
::supply that is feeding into the right triodes 1st grid.
::
::
::With that DC level sharing of the stages, that voltage level present at the #6 plate of the right triode will walk up and down in value, with any shift of that -150 supply buss level.
::
::
::A portion of that difference is tapped off via the R707-R706 resistive voltage divider to then feed
::in as a controlling and corrective grid bias, to the 1st grid of the V700 comparator stage.
::
::
::If there is a need for a voltage correction, from there being too high of a voltage presence at the
::-150 VDC buss sampling, the slight presence of a more positive voltage to the 1st grid of V700 then
::increases its conduction.
::
::
::More conduction in that V700 stage then means that the common V700 plate to 1st grid connection to
::the 12B4 trio is going to pull down on, and bleed down that grid turn on + level that is continually
::being provided via R729 from the +100 V supply.
::
::
::The end result is the soaking up of the excess voltage via the 12B4 cluster and the regulation of the output buss down to the prescribed -150VDC.
::
::
::
::
:: Regulation Technique Summation:
::
::
::
::
::The left V712 triode's 1st grid receives a sample of the stable voltage reference.
::
::
::
::The right V712 triode's 1st grid receives a sample of a segment of of -105 V supply buss level.
::
::
::
::They compare . . . and any variance from the norm will result in a shifting up or down of the plate
::
::supply voltage of the right triode of V712.
::
::
::
::That potentially variant voltage then feeds over to the 1st grid of the V700 comparator stage, its
::potentially variant grid biasing swing could then provide for more or less conduction in accordance
::as to whether it was making a + swing or a - swing.
::
::
::That varying degree of conduction at the plate of V700 IS ALSO directly tied into the 1st grids of the 12B4 triodes.
::
::
::
::
::Net Result . . . . would then be:
::
::
::
::
::If V700 conducts more heavily, it pulls down the normal + grid bias present on those 12B4 stages via the R729 supply resistor from the +100VDC supply.
::
::
::As they conduct less, that trio starts absorbing more of the surplus voltage presence, thus the -105 buss has a reduced voltage level presence, with it then shifting down to the specified -105 level.
::
::
::Same control effect on the other situation of the -105 supply output being at LESS that its desired output voltage level.
::In that situation the V700 would be needing to conduct LESS in order for there to be less pull down of the static + bias being fed into the 12B4's 1st grids.
::
::
::
::
::How to do-it-to-it:
::
::
::
::
::DVM probe to chassis ground, and then you use its other probe to 2-4 or 7 of the 5651 . . if you then find an ~87 V presence, the gas tube is firing and regulating as it should .
::
::
::
::
::Move metering to the center terminal of R716 pot [ -150 supply adjust ] and swing the pot thru its range, to confirm an according voltage swing on the meter. . .if so.
::
::
::
::
::Move metering to the Pin #6 plate of V712, keep up the same swinging of the R716 thru its range to see if there is a like variable response in the swinging of that plate level.. . .if so.
::
::
::
::
::Move metering to the Pin #1 1 st grid of the V700 comparator stage plate to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
::
::
::
::
::
::Move metering to the Pin #7 of V725 1st grid to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
::
::
::
::
::
::NOW, you MOVE metering over to being across Pin #1 and pin #9 of V725 to see what the maximum voltage developed is, at the setting of the -150 adjustment pot which results in the highest voltage reading.
::
::
::If that is not high enough, that is why your raw B+ level is not being able to be adjusted down to that -105 standard level.
::
::
::Go back and check the screen, plate, first grid and cathode voltages of the V700 and check for their variance from the schematics estimation of those voltages.
::
::
::
::
::
::ZUJ'ing
::
::
::
::
::
::
::
::73's de Edd
::
::
::


::

::
::
::
::
::
::
::
:

10/27/2009 4:39:31 PMEdd







Sir Joe. . .

I just noticed that in the FULL explanation of the "silver bearing solder" aspect, that I forgot to include the
additonal query of :




The last time I had it out I was going to replace the diodes in the HV section with semiconductor replacements
and put a resistor on each of the filaments.




In which, I would have to completely think that you were referring to THE high voltage section and its use of
the now somewhat pricey "pencil" rectifier tubes.


Now, there could be the dual consideration of either the use of the quite reliable selenium stack, stick rectifiers
that were used for a limited time frame, for use as focus rectifiers on color TV receivers, replacing the 1V2
family of vacuum tube rectifiers. They are down to about the $3 each price range now.


Otherwise, the use of a pure silicon high voltage diode / stack as its element.


When using the 5642's they were going to have the highest diode rectificaton loss, with the selenium stick stack
having a bit less of a conversion drop, with the silicon unit having but a VERY miniscule voltage drop.


The HV section is created at two levels with the tripling up to the ~8650 volt level highest level for the accelerator
anode of the CRT, and the lower ~1350 voltage supply being voltage divided for taking care of the multi voltage levels needed by the gun elements of the CRT.


I can see where the accelerator anode just might actually like that bit of additonal voltage.


On the voltage division of the High Voltages lower voltage level, that might or might not adjust in for that extra 50-100
extra volts now being available.


Seems like an initial try it and see situation, then the insertion of a series dropping resistor at a now dormant terminal
of a formerly unused filamant windings for a 5642.


If you don't happen to have a 25-50 K high voltage probe in order to exert minimal HV loading while extracting a total high
voltage reading, you could merely set up all controls, never move them, and take a reading across a lower voltage being derived from its arrangement in a series voltage divider string.


A good lower voltage level point would be on the voltage divider string of the focus supply resistor string, with attention
given to the cold side from ground at the R850 point as it is being referenced against ground.


Then you tack in the SS HV rectifier and see what that same voltage sample has now risen up to.


Then you initially tack in a series dropping resistor in a filament to diode leg and see by the resultant voltage at the "test"
node, if you then have to zip that resistance either on up or down from your initially guesstimated value to re establish
that initial voltage level that was being produced by the tube rectifiers.





Thassit . . . .




73's de Edd





:
:
:
:

:
:
:
:
:
:
:Sir Joe. . .
:
:
:
:
:
:Me thinks that the situation on the solder, was the simple consideration that if one . . .John Doe . . .Eng or Tekkie
:extra-ordinaire . . . . who wasn't working right in the instrumentation / calibration / repair field of expertise,
:would have a problem locating that solder , so they included some multiple loops of it within the instrument.
:Also might I clarify its somewhat misleading referencing to it as being "silver" solder.
:
:
:Which is a "hard" type of compilation of completely different metals , which requires "heat city" in getting it
:into its initial plastic state and then even more to get it on into the flowing and fusing state.
:
:
:The proper wording for the solder type we are referring to would be that of "silver bearing solder".
:
:
:
:
:The mentioned solder, being a slight variant of the electronics servicing blend of 60%tin / 40% lead or the
:upgrading to SUPER blend of the eutectic grade by the skewing of that blend to ~ 63%tin / 37% lead
:eutectic blend, where there is then the advantage of flowing into / out of a liquid/solid state with the absolute
:shortest transitional time.
:
:( Benefit . . . .less chance of a cold / fractured joint problem if subjected to a
:micro-movement during soldering cool down.)
:
:
:And then there is the mentioned silver bearing solder category which shifts the blend to potentially having
:up to a 5% silver content. That enhances conductivity, corrosion resistance and enhances "wettability".
:
:
:And now, as for the final " Cow-Pee-'De-Grass " on the pertinent info , would be the exacting reasoning on the
:desirability of using silver bearing solder on a units repair.
:
:
:I strongly believe that would PRINCIPALLY be directed towards soldering repairs involving their NEAT little,
:what I call . . .ceramic terminal "troughs" . . .which they came up with and started using in their construction
:of instrumentation. Probably being used in instruments up to the point where PCB construction then became
:the norm. With their possible retention in hard wiring sites that were not feasible to be incorporated on a PCB.
:
:
:
:
:
:
: . . . . . . Example of a TEK type of terminal strip.
:
:
:
:I don't currently have a strip on hand to mechanically and microscopically examine, but there are the separate
:silver troughs which are located within cutouts within the ceramic form. Anyone correct me if wrong, but it
:seems that waaaaay back in first generation they actually had silver OR copper, with silver plating that fit down
:within those slots within the ceramic. Seems like I had seen both the incorporation of both the flat looking bisque
:form of ceramic used and then some units having received a glaze and a firing to end up as being Hard----Shiny
:City as their end result.
:
:Assuredly those units would lean towards being used in Hi Voltage environs or in an area
:you would not want a solid condensation conductivity path from humidity on them.
:
:
:Now it seems that at point in time that they reverted to different type of construction, where they tried to simplify /
:automate the construction of the troughs .
:
:
:So it seems like that they might have taken a page from the potentiometer manufacturers where they would have
:the need of placing a conductive path on a ceramic blank, but could not get away with the mere use of a graphite slurry to perform condudction, as the pot manufacturers might have used. But the pot manufacturers also ran into particular
:situatons where they needed to solder a wire to a connection which was interfacing with circuitrty on a ceramic blank.
:I can remenber that in three different manners / stages of development.
:
:
:
:Technique #1:
:
:
:Initially there was the mechanical technique of having the "contact area" portion of the ceramic just being mechanically
:abraded with a coarse silicon carbide wheel , leaving a porous and somewhat rough surfacing in that area.
:
:
:( This being akin to the liberal roughing up of the somewhat shiny and glazed surfacing of an inner tube , before the then
:additon of rubber cement /vulcanizing agent , and the final pressing on of a patch.)
:
:
:If one then takes a spinning disk of soft copper and make a gradual pressing into the abraded surface, one can see it fill in
:the porous cavities and then start building up a smooth surface of copper.
:
:
:If one then has a build up of copper, and does not solder like an amateur, and facilitates by the use of flux, one then can
:build up a surfactally tinned contact area.
:
:
:It is then a piece of cake to take your connecting wire lead, strip it, pre tin it and then move over and reflow solder onto
:the pretinned contact area.
:
:
:Now just who said that you couldn't solder to ceramic . . . .or even GLASS for that matter.
:
:
:Oh, this just gets easier, since with silver , it is so soft and malleable, in comparison to that use of copper, that it really
:is much easier to use and permits an even more impressive ease of application and overall build up capability.
:
:
:Now . . . .ya wanna see me solder to ceramic ?
:
:
:That is the primary manner of interfacing connections to ceramic, that I remembered being utilized, but there was also:
:
:
:
:
:Technique #1:
:A variant similar to the "baby shoe bronzing" technique of placing a graphite coating on a nonconductor (leather baby
:shoe) /or /ceramic ? and then electroplating copper on the surface to an adequate build up level. Or in the case of the
:use of ceramic for making a connection terminus, the then placing of a silverplate onto the copper.
:
:
:
:
:Technique #3:
:Modern day technology, in the respect of having the contact area(s) of interest, being the only ones openly exposed,
:with all of the other area masked off. The ceramic unit is then placed in a vacuum bell and within, there is sacrificial
:silver that has a very high voltage and current arc developed across it. A full vacuum is then pulled within the bell
:the silver is the arced and totally vaporizes, a thin film of silver is deposited down within the porously abraded contact
:area. Multiple operations then build up the thicknesses of the deposited silver.
:
:
:
:
:I don't know the evolution of the maufacture of the Tek terminal "trough" strip, but would guess that the day one
:consideration of a silver insert into a ceramic block and its economic variants of using less silver content and
:eventually silver plate. And then, the sheer volume of quantity used and the need of a speedier as well as more
:economical manufacturing mode might have led to a variant of the interfacing to ceramic as was used by the
:potentiometer / control manufacturers.
:
:
:At least in the controls situation, they can have a terminal area and then a degree of termal isolation where a
:deposition of a slurry of graphite could interface between that terminal and a resistive contact strip of the control.
:
:
:
:Even back at the manufacturing point of having a contact divot swaged or imbedded into a bisque ceramic block
:and then fired, that might seem to be the necessary technique to make a solid mechanical interfacing and yet
:hold up to some of the errant degree of overheating that it might be subjected to by SOME repair persons.
:
:
:I have never quite found a family of epoxy which would hold up to extended soldering iron heat levels, other
: than fast reflow operations. (Even the industrial E-pon and Hy-Sol families.)
:
:
:Keep the soldering heat on too long on an epoxy anchored terminal and the bubbles will flow out from it.
:
:
:
:
:Soooooo this all resulted in a full technical fill in . .why for . . as to the query about the use of silver bearing
:solder on repairs, with my thinking that the full consideration might precisely be just related to those terminal
:"troughs" in the aspect of placing soldering iron heat on those terminal "troughs" and then the pulling out of
:solder clad leads of associative components from them and placing in new component leads.
:
:
:THEN, if you should be using a common solder, to then flow a great new anount of it down to fill in the "trough"
:the potential is there for that plain solder to leech out . .and carry away . . .some of that silver which is interfacing
:in the bonding to the ceramic substrate, thus weakening its bond integrity.
:
:
:The use of a silver bearing solder would profusely abate that proclivity.
:
:
:Thassit . . . . .
:
:
:
:
:
:
:73's de Edd
:
:
:


:

:
:
:
:
:
:
:::
:::

:::
:::
:::
:::Hey,
::I just dug my 545A out and will start working on it.
::The last time I had it out I was going to replace the diodes in the HV section with semiconductor replacements and put a resistor on each of the filaments. My big question is do you have to use Silver solder in the HV section only and the rest of the unit 60/40?
::
::Thanks,
::Joe
::
::
:::
:::
:::Sir David. . . .
:::
:::
:::
:::Well here we are again exploring yet another branch on the total repair aspect. Wayyy back
:::on day one, was not my first few "breaths " from my keyboard being relevant to the confirmantion
:::of the presence and tolerances of ALL of the LVPS's developed supply voltages?
:::
:::
:::
:::
:::That, even being with a very detailed explanation of all of the supply voltages, and the
:::dependent fact that almost all were "electrically interlocked" to each other
:::
:::
:::
:::That which you are running up against now is the fact that the hoz positioning, is
:::related to a capability of needing a completely seamless shift of a DC voltage. Now that
:::might be dependent, at one point, of a swing down from being a +DC voltage and down to
:::a zero voltage axis and then a swing onto a transitional shift into being a - voltage
:::level.
:::
:::
:::Remember, this scope extensively uses DC coupled differential stages which are dependent upon
:::use of bipolar supplies.
:::
:::
:::Alas, your -150 supply is a bit higher than its prescribed level so that is upsetting other conditons, since it is used in so many other portions of the set.
:::
:::
:::
:::
:::ADJUNCT ASIDE:
:::
:::
:::
:::I don't remember the units hoz positioning control, being other than the common dual
:::concentric control, that is using a high value pot along with a smaller pot such that the combo
:::gives a coarse and vernier adjustment capability.
:::
:::
:::You then just place the start of trace, at the very left graticule indexing of the grid display matrix.
:::
:::
:::
:::
:::Now you ALSO have a Helipot control on the front panel in the form of the vernier delay adjustment
:::of the B mode time delay onset, if using the "B" delayed sweep functions capability of the unit.
:::
:::
:::It would NOT be relevant to you at all, until you get this unit percolating, you will be placing
:::the HOZ sweep option switch at its very top, upper,center "A" sweep mode option.
:::
:::
:::
:::
:::Let me now go into a detail of the basic operation principle of the - 150 supply.
:::
:::
:::
:::Seems like that I tacked the LVPS Supply Working Schematic on to many different points, but
:::this one seems to kick right in . . .unless on rural- party line - hand crank- dial up . . . .meet
:::you here, same time on Thursday !
:::
:::
:::Seek out:
:::
:::http://www.nostalgiaair.org/Forums/Messages/530/M0080530.htm
:::
:::
:::
:::
:::Looking at the -150 supply portion, and reiterating again, the - supply line is a direct
:::connection from - line of the DC raw supply, with no inline obstructions, with it then emerging
:::at the far right, as being the designated -150 supply terminus.
:::
:::
:::And NOW, the positive portion of the raw DC supply, is then feeding on over to the plates of
:::a triad bank of (3) 12B4 power reg tubes.
:::
:::
:::
:::
:::The basic regulation concept of this stage is dependent upon that trio of tubes experiencing
:::an initial turn on with their 1st grids conduction biasing being acquired via that R729 which
:::you see going up to its supply source . . .the +110 regulated supply source, so
:::now I ask you . . . . GOT MILK ? . .errrr make that +100 VDC supply voltage ?
:::
:::
:::As it stands, if that bias voltage is present and is unhampered, the 12B4 trio would be driven
:::into so full of a degree of conduction, that there would only be the voltage drop across the
:::plate-cathode of the tubes that is making a path to ground via the cathodes.
:::
:::
:::In that conditon, the supply would be having a MUCH-MUCH greater output voltage than the desired
:::-150 VDC benchmark.
:::( . .BTW . . .Now, isn't that the EXACT condition which you are now experiencing ?)
:::
:::
:::Soooooo go back to the schema and notice the daisy chaining of all of the 12B4 1st grids, along with
:::their final emergence being over to the left and downwards to the plate of the V700 comparator stage
:::where,in actuality, it is then providing that stages plate supply voltage also.
:::
:::
:::Then, there is a straight forward technique in the screen voltage acquisition for that V700 stage.
:::
:::
:::When looking at its 1st grid control voltage, we see it as being routed in from a tap off
:::of a resistive voltage divider(R707-706) that is going over to connect across the plate of a DC
:::differential pair- DC coupled amplifier stage.
:::
:::
:::That same plate is receiving ITS supply voltage via the R719 resistor from the + 100 VDC supply.
:::
:::
:::The idea now in the regulation aspect, is for that 12B4 trio to not FULLY conduct, but to only
:::partially conduct, such that they can be responsible for creating the voltage drop which decreases that initial FULL raw DC supply, on down to the required -150 volt level.
:::
:::
:::
:::That is being accomplished by two conditions, initially by the aquisition of a stable voltage reference source to input at the 1st grid of the left triode of that V712 differential DC amp stage.
:::
:::
:::Notice the presence of the 5651 gas tube regulator, being placed between the negative supply buss and a current limiting resistor R710, a complete series power loop is then made by the final connection of the other electrode of the 5651 to ground.
:::
:::
:::There is then the series resistor isolation that is provided by resistor R711 and the final presence of a slightly dropped initial ~87 voltage level that was developed across the conducting 5651 gaseous regulator reference.
:::
:::
:::The next aspect then would be the right half triode of V712 where its plate is receiving its supply from the R719 resistor.
:::
:::
:::Look now at the R718-R716-R715 voltage divider trio, with their interrelated RATIO of values, being chosen such that a min and max of adjustment range limits could be acquired.
:::
:::
:::That sampling across the -105 VDC output voltage , is fed on in thru isolative resistor R717 and then
:::presents a sampled volage to the 1st grid of the right triode of the diferential pair.
:::
:::
:::Note that the pair of triodes cathodes are tied together and then sharing a common cathode resistor.
:::Look and see the fixed voltage reference over at the left triodes first grid.
:::
:::
:::Also see the voltage dividers sample of the level of voltage present across the -150VDC
:::supply that is feeding into the right triodes 1st grid.
:::
:::
:::With that DC level sharing of the stages, that voltage level present at the #6 plate of the right triode will walk up and down in value, with any shift of that -150 supply buss level.
:::
:::
:::A portion of that difference is tapped off via the R707-R706 resistive voltage divider to then feed
:::in as a controlling and corrective grid bias, to the 1st grid of the V700 comparator stage.
:::
:::
:::If there is a need for a voltage correction, from there being too high of a voltage presence at the
:::-150 VDC buss sampling, the slight presence of a more positive voltage to the 1st grid of V700 then
:::increases its conduction.
:::
:::
:::More conduction in that V700 stage then means that the common V700 plate to 1st grid connection to
:::the 12B4 trio is going to pull down on, and bleed down that grid turn on + level that is continually
:::being provided via R729 from the +100 V supply.
:::
:::
:::The end result is the soaking up of the excess voltage via the 12B4 cluster and the regulation of the output buss down to the prescribed -150VDC.
:::
:::
:::
:::
::: Regulation Technique Summation:
:::
:::
:::
:::
:::The left V712 triode's 1st grid receives a sample of the stable voltage reference.
:::
:::
:::
:::The right V712 triode's 1st grid receives a sample of a segment of of -105 V supply buss level.
:::
:::
:::
:::They compare . . . and any variance from the norm will result in a shifting up or down of the plate
:::
:::supply voltage of the right triode of V712.
:::
:::
:::
:::That potentially variant voltage then feeds over to the 1st grid of the V700 comparator stage, its
:::potentially variant grid biasing swing could then provide for more or less conduction in accordance
:::as to whether it was making a + swing or a - swing.
:::
:::
:::That varying degree of conduction at the plate of V700 IS ALSO directly tied into the 1st grids of the 12B4 triodes.
:::
:::
:::
:::
:::Net Result . . . . would then be:
:::
:::
:::
:::
:::If V700 conducts more heavily, it pulls down the normal + grid bias present on those 12B4 stages via the R729 supply resistor from the +100VDC supply.
:::
:::
:::As they conduct less, that trio starts absorbing more of the surplus voltage presence, thus the -105 buss has a reduced voltage level presence, with it then shifting down to the specified -105 level.
:::
:::
:::Same control effect on the other situation of the -105 supply output being at LESS that its desired output voltage level.
:::In that situation the V700 would be needing to conduct LESS in order for there to be less pull down of the static + bias being fed into the 12B4's 1st grids.
:::
:::
:::
:::
:::How to do-it-to-it:
:::
:::
:::
:::
:::DVM probe to chassis ground, and then you use its other probe to 2-4 or 7 of the 5651 . . if you then find an ~87 V presence, the gas tube is firing and regulating as it should .
:::
:::
:::
:::
:::Move metering to the center terminal of R716 pot [ -150 supply adjust ] and swing the pot thru its range, to confirm an according voltage swing on the meter. . .if so.
:::
:::
:::
:::
:::Move metering to the Pin #6 plate of V712, keep up the same swinging of the R716 thru its range to see if there is a like variable response in the swinging of that plate level.. . .if so.
:::
:::
:::
:::
:::Move metering to the Pin #1 1 st grid of the V700 comparator stage plate to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:::
:::
:::
:::
:::
:::Move metering to the Pin #7 of V725 1st grid to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:::
:::
:::
:::
:::
:::NOW, you MOVE metering over to being across Pin #1 and pin #9 of V725 to see what the maximum voltage developed is, at the setting of the -150 adjustment pot which results in the highest voltage reading.
:::
:::
:::If that is not high enough, that is why your raw B+ level is not being able to be adjusted down to that -105 standard level.
:::
:::
:::Go back and check the screen, plate, first grid and cathode voltages of the V700 and check for their variance from the schematics estimation of those voltages.
:::
:::
:::
:::
:::
:::ZUJ'ing
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::


:::

:::
:::
:::
:::
:::
:::
:::
::
:
10/27/2009 5:12:31 PMJoe Wutsch
Thanks Edd!
I have a set of Silicon Diodes that I bought about 15 years ago for this unit.
All the 5642's have their leads broken right at the glass envelope and I ground a bit off to get a connection but all I got was the "Arc of the Covenant"

Joe

10/27/2009 4:06:34 PMDave Froehlich
Edd,
I will have to disconnect that R756 to make any measurements. Even without the plug-in, this resistor smokes, and no load can be found.
I will do the testing you recommend later this evening.

Thanks very much,

Dave
:
:

:
:
:
:
:
:
:Sir David. . . .
:
:
:
:Well here we are again exploring yet another branch on the total repair aspect. Wayyy back
:on day one, was not my first few "breaths " from my keyboard being relevant to the confirmantion
:of the presence and tolerances of ALL of the LVPS's developed supply voltages?
:
:
:
:
:That, even being with a very detailed explanation of all of the supply voltages, and the
:dependent fact that almost all were "electrically interlocked" to each other
:
:
:
:That which you are running up against now is the fact that the hoz positioning, is
:related to a capability of needing a completely seamless shift of a DC voltage. Now that
:might be dependent, at one point, of a swing down from being a +DC voltage and down to
:a zero voltage axis and then a swing onto a transitional shift into being a - voltage
:level.
:
:
:Remember, this scope extensively uses DC coupled differential stages which are dependent upon
:use of bipolar supplies.
:
:
:Alas, your -150 supply is a bit higher than its prescribed level so that is upsetting other conditons, since it is used in so many other portions of the set.
:
:
:
:
:ADJUNCT ASIDE:
:
:
:
:I don't remember the units hoz positioning control, being other than the common dual
:concentric control, that is using a high value pot along with a smaller pot such that the combo
:gives a coarse and vernier adjustment capability.
:
:
:You then just place the start of trace, at the very left graticule indexing of the grid display matrix.
:
:
:
:
:Now you ALSO have a Helipot control on the front panel in the form of the vernier delay adjustment
:of the B mode time delay onset, if using the "B" delayed sweep functions capability of the unit.
:
:
:It would NOT be relevant to you at all, until you get this unit percolating, you will be placing
:the HOZ sweep option switch at its very top, upper,center "A" sweep mode option.
:
:
:
:
:Let me now go into a detail of the basic operation principle of the - 150 supply.
:
:
:
:Seems like that I tacked the LVPS Supply Working Schematic on to many different points, but
:this one seems to kick right in . . .unless on rural- party line - hand crank- dial up . . . .meet
:you here, same time on Thursday !
:
:
:Seek out:
:
:http://www.nostalgiaair.org/Forums/Messages/530/M0080530.htm
:
:
:
:
:Looking at the -150 supply portion, and reiterating again, the - supply line is a direct
:connection from - line of the DC raw supply, with no inline obstructions, with it then emerging
:at the far right, as being the designated -150 supply terminus.
:
:
:And NOW, the positive portion of the raw DC supply, is then feeding on over to the plates of
:a triad bank of (3) 12B4 power reg tubes.
:
:
:
:
:The basic regulation concept of this stage is dependent upon that trio of tubes experiencing
:an initial turn on with their 1st grids conduction biasing being acquired via that R729 which
:you see going up to its supply source . . .the +110 regulated supply source, so
:now I ask you . . . . GOT MILK ? . .errrr make that +100 VDC supply voltage ?
:
:
:As it stands, if that bias voltage is present and is unhampered, the 12B4 trio would be driven
:into so full of a degree of conduction, that there would only be the voltage drop across the
:plate-cathode of the tubes that is making a path to ground via the cathodes.
:
:
:In that conditon, the supply would be having a MUCH-MUCH greater output voltage than the desired
:-150 VDC benchmark.
:( . .BTW . . .Now, isn't that the EXACT condition which you are now experiencing ?)
:
:
:Soooooo go back to the schema and notice the daisy chaining of all of the 12B4 1st grids, along with
:their final emergence being over to the left and downwards to the plate of the V700 comparator stage
:where,in actuality, it is then providing that stages plate supply voltage also.
:
:
:Then, there is a straight forward technique in the screen voltage acquisition for that V700 stage.
:
:
:When looking at its 1st grid control voltage, we see it as being routed in from a tap off
:of a resistive voltage divider(R707-706) that is going over to connect across the plate of a DC
:differential pair- DC coupled amplifier stage.
:
:
:That same plate is receiving ITS supply voltage via the R719 resistor from the + 100 VDC supply.
:
:
:The idea now in the regulation aspect, is for that 12B4 trio to not FULLY conduct, but to only
:partially conduct, such that they can be responsible for creating the voltage drop which decreases that initial FULL raw DC supply, on down to the required -150 volt level.
:
:
:
:That is being accomplished by two conditions, initially by the aquisition of a stable voltage reference source to input at the 1st grid of the left triode of that V712 differential DC amp stage.
:
:
:Notice the presence of the 5651 gas tube regulator, being placed between the negative supply buss and a current limiting resistor R710, a complete series power loop is then made by the final connection of the other electrode of the 5651 to ground.
:
:
:There is then the series resistor isolation that is provided by resistor R711 and the final presence of a slightly dropped initial ~87 voltage level that was developed across the conducting 5651 gaseous regulator reference.
:
:
:The next aspect then would be the right half triode of V712 where its plate is receiving its supply from the R719 resistor.
:
:
:Look now at the R718-R716-R715 voltage divider trio, with their interrelated RATIO of values, being chosen such that a min and max of adjustment range limits could be acquired.
:
:
:That sampling across the -105 VDC output voltage , is fed on in thru isolative resistor R717 and then
:presents a sampled volage to the 1st grid of the right triode of the diferential pair.
:
:
:Note that the pair of triodes cathodes are tied together and then sharing a common cathode resistor.
:Look and see the fixed voltage reference over at the left triodes first grid.
:
:
:Also see the voltage dividers sample of the level of voltage present across the -150VDC
:supply that is feeding into the right triodes 1st grid.
:
:
:With that DC level sharing of the stages, that voltage level present at the #6 plate of the right triode will walk up and down in value, with any shift of that -150 supply buss level.
:
:
:A portion of that difference is tapped off via the R707-R706 resistive voltage divider to then feed
:in as a controlling and corrective grid bias, to the 1st grid of the V700 comparator stage.
:
:
:If there is a need for a voltage correction, from there being too high of a voltage presence at the
:-150 VDC buss sampling, the slight presence of a more positive voltage to the 1st grid of V700 then
:increases its conduction.
:
:
:More conduction in that V700 stage then means that the common V700 plate to 1st grid connection to
:the 12B4 trio is going to pull down on, and bleed down that grid turn on + level that is continually
:being provided via R729 from the +100 V supply.
:
:
:The end result is the soaking up of the excess voltage via the 12B4 cluster and the regulation of the output buss down to the prescribed -150VDC.
:
:
:
:
: Regulation Technique Summation:
:
:
:
:
:The left V712 triode's 1st grid receives a sample of the stable voltage reference.
:
:
:
:The right V712 triode's 1st grid receives a sample of a segment of of -105 V supply buss level.
:
:
:
:They compare . . . and any variance from the norm will result in a shifting up or down of the plate
:
:supply voltage of the right triode of V712.
:
:
:
:That potentially variant voltage then feeds over to the 1st grid of the V700 comparator stage, its
:potentially variant grid biasing swing could then provide for more or less conduction in accordance
:as to whether it was making a + swing or a - swing.
:
:
:That varying degree of conduction at the plate of V700 IS ALSO directly tied into the 1st grids of the 12B4 triodes.
:
:
:
:
:Net Result . . . . would then be:
:
:
:
:
:If V700 conducts more heavily, it pulls down the normal + grid bias present on those 12B4 stages via the R729 supply resistor from the +100VDC supply.
:
:
:As they conduct less, that trio starts absorbing more of the surplus voltage presence, thus the -105 buss has a reduced voltage level presence, with it then shifting down to the specified -105 level.
:
:
:Same control effect on the other situation of the -105 supply output being at LESS that its desired output voltage level.
:In that situation the V700 would be needing to conduct LESS in order for there to be less pull down of the static + bias being fed into the 12B4's 1st grids.
:
:
:
:
:How to do-it-to-it:
:
:
:
:
:DVM probe to chassis ground, and then you use its other probe to 2-4 or 7 of the 5651 . . if you then find an ~87 V presence, the gas tube is firing and regulating as it should .
:
:
:
:
:Move metering to the center terminal of R716 pot [ -150 supply adjust ] and swing the pot thru its range, to confirm an according voltage swing on the meter. . .if so.
:
:
:
:
:Move metering to the Pin #6 plate of V712, keep up the same swinging of the R716 thru its range to see if there is a like variable response in the swinging of that plate level.. . .if so.
:
:
:
:
:Move metering to the Pin #1 1 st grid of the V700 comparator stage plate to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:
:
:
:
:
:Move metering to the Pin #7 of V725 1st grid to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:
:
:
:
:
:NOW, you MOVE metering over to being across Pin #1 and pin #9 of V725 to see what the maximum voltage developed is, at the setting of the -150 adjustment pot which results in the highest voltage reading.
:
:
:If that is not high enough, that is why your raw B+ level is not being able to be adjusted down to that -105 standard level.
:
:
:Go back and check the screen, plate, first grid and cathode voltages of the V700 and check for their variance from the schematics estimation of those voltages.
:
:
:
:
:
:ZUJ'ing
:
:
:
:
:
:
:
:73's de Edd
:
:
:


:

:
:
:
:
:
:
:

10/27/2009 4:46:17 PMDave Froehlich
Edd,
Is it ok to unplug the Horizontal Oscillator tube so the HV is off when I measure the power supply?

Thanks,

Dave
:
:

:
:
:
:
:
:
:Sir David. . . .
:
:
:
:Well here we are again exploring yet another branch on the total repair aspect. Wayyy back
:on day one, was not my first few "breaths " from my keyboard being relevant to the confirmantion
:of the presence and tolerances of ALL of the LVPS's developed supply voltages?
:
:
:
:
:That, even being with a very detailed explanation of all of the supply voltages, and the
:dependent fact that almost all were "electrically interlocked" to each other
:
:
:
:That which you are running up against now is the fact that the hoz positioning, is
:related to a capability of needing a completely seamless shift of a DC voltage. Now that
:might be dependent, at one point, of a swing down from being a +DC voltage and down to
:a zero voltage axis and then a swing onto a transitional shift into being a - voltage
:level.
:
:
:Remember, this scope extensively uses DC coupled differential stages which are dependent upon
:use of bipolar supplies.
:
:
:Alas, your -150 supply is a bit higher than its prescribed level so that is upsetting other conditons, since it is used in so many other portions of the set.
:
:
:
:
:ADJUNCT ASIDE:
:
:
:
:I don't remember the units hoz positioning control, being other than the common dual
:concentric control, that is using a high value pot along with a smaller pot such that the combo
:gives a coarse and vernier adjustment capability.
:
:
:You then just place the start of trace, at the very left graticule indexing of the grid display matrix.
:
:
:
:
:Now you ALSO have a Helipot control on the front panel in the form of the vernier delay adjustment
:of the B mode time delay onset, if using the "B" delayed sweep functions capability of the unit.
:
:
:It would NOT be relevant to you at all, until you get this unit percolating, you will be placing
:the HOZ sweep option switch at its very top, upper,center "A" sweep mode option.
:
:
:
:
:Let me now go into a detail of the basic operation principle of the - 150 supply.
:
:
:
:Seems like that I tacked the LVPS Supply Working Schematic on to many different points, but
:this one seems to kick right in . . .unless on rural- party line - hand crank- dial up . . . .meet
:you here, same time on Thursday !
:
:
:Seek out:
:
:http://www.nostalgiaair.org/Forums/Messages/530/M0080530.htm
:
:
:
:
:Looking at the -150 supply portion, and reiterating again, the - supply line is a direct
:connection from - line of the DC raw supply, with no inline obstructions, with it then emerging
:at the far right, as being the designated -150 supply terminus.
:
:
:And NOW, the positive portion of the raw DC supply, is then feeding on over to the plates of
:a triad bank of (3) 12B4 power reg tubes.
:
:
:
:
:The basic regulation concept of this stage is dependent upon that trio of tubes experiencing
:an initial turn on with their 1st grids conduction biasing being acquired via that R729 which
:you see going up to its supply source . . .the +110 regulated supply source, so
:now I ask you . . . . GOT MILK ? . .errrr make that +100 VDC supply voltage ?
:
:
:As it stands, if that bias voltage is present and is unhampered, the 12B4 trio would be driven
:into so full of a degree of conduction, that there would only be the voltage drop across the
:plate-cathode of the tubes that is making a path to ground via the cathodes.
:
:
:In that conditon, the supply would be having a MUCH-MUCH greater output voltage than the desired
:-150 VDC benchmark.
:( . .BTW . . .Now, isn't that the EXACT condition which you are now experiencing ?)
:
:
:Soooooo go back to the schema and notice the daisy chaining of all of the 12B4 1st grids, along with
:their final emergence being over to the left and downwards to the plate of the V700 comparator stage
:where,in actuality, it is then providing that stages plate supply voltage also.
:
:
:Then, there is a straight forward technique in the screen voltage acquisition for that V700 stage.
:
:
:When looking at its 1st grid control voltage, we see it as being routed in from a tap off
:of a resistive voltage divider(R707-706) that is going over to connect across the plate of a DC
:differential pair- DC coupled amplifier stage.
:
:
:That same plate is receiving ITS supply voltage via the R719 resistor from the + 100 VDC supply.
:
:
:The idea now in the regulation aspect, is for that 12B4 trio to not FULLY conduct, but to only
:partially conduct, such that they can be responsible for creating the voltage drop which decreases that initial FULL raw DC supply, on down to the required -150 volt level.
:
:
:
:That is being accomplished by two conditions, initially by the aquisition of a stable voltage reference source to input at the 1st grid of the left triode of that V712 differential DC amp stage.
:
:
:Notice the presence of the 5651 gas tube regulator, being placed between the negative supply buss and a current limiting resistor R710, a complete series power loop is then made by the final connection of the other electrode of the 5651 to ground.
:
:
:There is then the series resistor isolation that is provided by resistor R711 and the final presence of a slightly dropped initial ~87 voltage level that was developed across the conducting 5651 gaseous regulator reference.
:
:
:The next aspect then would be the right half triode of V712 where its plate is receiving its supply from the R719 resistor.
:
:
:Look now at the R718-R716-R715 voltage divider trio, with their interrelated RATIO of values, being chosen such that a min and max of adjustment range limits could be acquired.
:
:
:That sampling across the -105 VDC output voltage , is fed on in thru isolative resistor R717 and then
:presents a sampled volage to the 1st grid of the right triode of the diferential pair.
:
:
:Note that the pair of triodes cathodes are tied together and then sharing a common cathode resistor.
:Look and see the fixed voltage reference over at the left triodes first grid.
:
:
:Also see the voltage dividers sample of the level of voltage present across the -150VDC
:supply that is feeding into the right triodes 1st grid.
:
:
:With that DC level sharing of the stages, that voltage level present at the #6 plate of the right triode will walk up and down in value, with any shift of that -150 supply buss level.
:
:
:A portion of that difference is tapped off via the R707-R706 resistive voltage divider to then feed
:in as a controlling and corrective grid bias, to the 1st grid of the V700 comparator stage.
:
:
:If there is a need for a voltage correction, from there being too high of a voltage presence at the
:-150 VDC buss sampling, the slight presence of a more positive voltage to the 1st grid of V700 then
:increases its conduction.
:
:
:More conduction in that V700 stage then means that the common V700 plate to 1st grid connection to
:the 12B4 trio is going to pull down on, and bleed down that grid turn on + level that is continually
:being provided via R729 from the +100 V supply.
:
:
:The end result is the soaking up of the excess voltage via the 12B4 cluster and the regulation of the output buss down to the prescribed -150VDC.
:
:
:
:
: Regulation Technique Summation:
:
:
:
:
:The left V712 triode's 1st grid receives a sample of the stable voltage reference.
:
:
:
:The right V712 triode's 1st grid receives a sample of a segment of of -105 V supply buss level.
:
:
:
:They compare . . . and any variance from the norm will result in a shifting up or down of the plate
:
:supply voltage of the right triode of V712.
:
:
:
:That potentially variant voltage then feeds over to the 1st grid of the V700 comparator stage, its
:potentially variant grid biasing swing could then provide for more or less conduction in accordance
:as to whether it was making a + swing or a - swing.
:
:
:That varying degree of conduction at the plate of V700 IS ALSO directly tied into the 1st grids of the 12B4 triodes.
:
:
:
:
:Net Result . . . . would then be:
:
:
:
:
:If V700 conducts more heavily, it pulls down the normal + grid bias present on those 12B4 stages via the R729 supply resistor from the +100VDC supply.
:
:
:As they conduct less, that trio starts absorbing more of the surplus voltage presence, thus the -105 buss has a reduced voltage level presence, with it then shifting down to the specified -105 level.
:
:
:Same control effect on the other situation of the -105 supply output being at LESS that its desired output voltage level.
:In that situation the V700 would be needing to conduct LESS in order for there to be less pull down of the static + bias being fed into the 12B4's 1st grids.
:
:
:
:
:How to do-it-to-it:
:
:
:
:
:DVM probe to chassis ground, and then you use its other probe to 2-4 or 7 of the 5651 . . if you then find an ~87 V presence, the gas tube is firing and regulating as it should .
:
:
:
:
:Move metering to the center terminal of R716 pot [ -150 supply adjust ] and swing the pot thru its range, to confirm an according voltage swing on the meter. . .if so.
:
:
:
:
:Move metering to the Pin #6 plate of V712, keep up the same swinging of the R716 thru its range to see if there is a like variable response in the swinging of that plate level.. . .if so.
:
:
:
:
:Move metering to the Pin #1 1 st grid of the V700 comparator stage plate to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:
:
:
:
:
:Move metering to the Pin #7 of V725 1st grid to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
:
:
:
:
:
:NOW, you MOVE metering over to being across Pin #1 and pin #9 of V725 to see what the maximum voltage developed is, at the setting of the -150 adjustment pot which results in the highest voltage reading.
:
:
:If that is not high enough, that is why your raw B+ level is not being able to be adjusted down to that -105 standard level.
:
:
:Go back and check the screen, plate, first grid and cathode voltages of the V700 and check for their variance from the schematics estimation of those voltages.
:
:
:
:
:
:ZUJ'ing
:
:
:
:
:
:
:
:73's de Edd
:
:
:


:

:
:
:
:
:
:
:

10/27/2009 5:32:13 PMEdd








Is it ok to unplug the Horizontal Oscillator tube so the HV is off when I measure the power supply?



Sir David . . .



I can't be LEAD- PIPE- CINCH . . . certain, with some very-very-very slight possibility of a voltage interlock /
disabling feature. (I'm in dummy mode now, Cuz I can't access and check out the WHOLE schematic at this instant.)


But, would think that it would be permissible, since 90 % of the AC line power transformer derivation is being
routed to use for the "regulated " supplies aspect.


That OSC circuit does account for a quarter of the power dissipation of the unit, in line just after the MYRIAD
of AMPS being consumed for the units filamental supplies.
How's bout you unplugging that little puppy and we done gwine to be findings out.

(PSSSSSSSHHHHT . . .the sound of searing fingertips and the distinctive aroma of burnt flesh.)



73's de Edd




:
:Dave
::
::

::
::
::
::
::
::
::Sir David. . . .
::
::
::
::Well here we are again exploring yet another branch on the total repair aspect. Wayyy back
::on day one, was not my first few "breaths " from my keyboard being relevant to the confirmantion
::of the presence and tolerances of ALL of the LVPS's developed supply voltages?
::
::
::
::
::That, even being with a very detailed explanation of all of the supply voltages, and the
::dependent fact that almost all were "electrically interlocked" to each other
::
::
::
::That which you are running up against now is the fact that the hoz positioning, is
::related to a capability of needing a completely seamless shift of a DC voltage. Now that
::might be dependent, at one point, of a swing down from being a +DC voltage and down to
::a zero voltage axis and then a swing onto a transitional shift into being a - voltage
::level.
::
::
::Remember, this scope extensively uses DC coupled differential stages which are dependent upon
::use of bipolar supplies.
::
::
::Alas, your -150 supply is a bit higher than its prescribed level so that is upsetting other conditons, since it is used in so many other portions of the set.
::
::
::
::
::ADJUNCT ASIDE:
::
::
::
::I don't remember the units hoz positioning control, being other than the common dual
::concentric control, that is using a high value pot along with a smaller pot such that the combo
::gives a coarse and vernier adjustment capability.
::
::
::You then just place the start of trace, at the very left graticule indexing of the grid display matrix.
::
::
::
::
::Now you ALSO have a Helipot control on the front panel in the form of the vernier delay adjustment
::of the B mode time delay onset, if using the "B" delayed sweep functions capability of the unit.
::
::
::It would NOT be relevant to you at all, until you get this unit percolating, you will be placing
::the HOZ sweep option switch at its very top, upper,center "A" sweep mode option.
::
::
::
::
::Let me now go into a detail of the basic operation principle of the - 150 supply.
::
::
::
::Seems like that I tacked the LVPS Supply Working Schematic on to many different points, but
::this one seems to kick right in . . .unless on rural- party line - hand crank- dial up . . . .meet
::you here, same time on Thursday !
::
::
::Seek out:
::
::http://www.nostalgiaair.org/Forums/Messages/530/M0080530.htm
::
::
::
::
::Looking at the -150 supply portion, and reiterating again, the - supply line is a direct
::connection from - line of the DC raw supply, with no inline obstructions, with it then emerging
::at the far right, as being the designated -150 supply terminus.
::
::
::And NOW, the positive portion of the raw DC supply, is then feeding on over to the plates of
::a triad bank of (3) 12B4 power reg tubes.
::
::
::
::
::The basic regulation concept of this stage is dependent upon that trio of tubes experiencing
::an initial turn on with their 1st grids conduction biasing being acquired via that R729 which
::you see going up to its supply source . . .the +110 regulated supply source, so
::now I ask you . . . . GOT MILK ? . .errrr make that +100 VDC supply voltage ?
::
::
::As it stands, if that bias voltage is present and is unhampered, the 12B4 trio would be driven
::into so full of a degree of conduction, that there would only be the voltage drop across the
::plate-cathode of the tubes that is making a path to ground via the cathodes.
::
::
::In that conditon, the supply would be having a MUCH-MUCH greater output voltage than the desired
::-150 VDC benchmark.
::( . .BTW . . .Now, isn't that the EXACT condition which you are now experiencing ?)
::
::
::Soooooo go back to the schema and notice the daisy chaining of all of the 12B4 1st grids, along with
::their final emergence being over to the left and downwards to the plate of the V700 comparator stage
::where,in actuality, it is then providing that stages plate supply voltage also.
::
::
::Then, there is a straight forward technique in the screen voltage acquisition for that V700 stage.
::
::
::When looking at its 1st grid control voltage, we see it as being routed in from a tap off
::of a resistive voltage divider(R707-706) that is going over to connect across the plate of a DC
::differential pair- DC coupled amplifier stage.
::
::
::That same plate is receiving ITS supply voltage via the R719 resistor from the + 100 VDC supply.
::
::
::The idea now in the regulation aspect, is for that 12B4 trio to not FULLY conduct, but to only
::partially conduct, such that they can be responsible for creating the voltage drop which decreases that initial FULL raw DC supply, on down to the required -150 volt level.
::
::
::
::That is being accomplished by two conditions, initially by the aquisition of a stable voltage reference source to input at the 1st grid of the left triode of that V712 differential DC amp stage.
::
::
::Notice the presence of the 5651 gas tube regulator, being placed between the negative supply buss and a current limiting resistor R710, a complete series power loop is then made by the final connection of the other electrode of the 5651 to ground.
::
::
::There is then the series resistor isolation that is provided by resistor R711 and the final presence of a slightly dropped initial ~87 voltage level that was developed across the conducting 5651 gaseous regulator reference.
::
::
::The next aspect then would be the right half triode of V712 where its plate is receiving its supply from the R719 resistor.
::
::
::Look now at the R718-R716-R715 voltage divider trio, with their interrelated RATIO of values, being chosen such that a min and max of adjustment range limits could be acquired.
::
::
::That sampling across the -105 VDC output voltage , is fed on in thru isolative resistor R717 and then
::presents a sampled volage to the 1st grid of the right triode of the diferential pair.
::
::
::Note that the pair of triodes cathodes are tied together and then sharing a common cathode resistor.
::Look and see the fixed voltage reference over at the left triodes first grid.
::
::
::Also see the voltage dividers sample of the level of voltage present across the -150VDC
::supply that is feeding into the right triodes 1st grid.
::
::
::With that DC level sharing of the stages, that voltage level present at the #6 plate of the right triode will walk up and down in value, with any shift of that -150 supply buss level.
::
::
::A portion of that difference is tapped off via the R707-R706 resistive voltage divider to then feed
::in as a controlling and corrective grid bias, to the 1st grid of the V700 comparator stage.
::
::
::If there is a need for a voltage correction, from there being too high of a voltage presence at the
::-150 VDC buss sampling, the slight presence of a more positive voltage to the 1st grid of V700 then
::increases its conduction.
::
::
::More conduction in that V700 stage then means that the common V700 plate to 1st grid connection to
::the 12B4 trio is going to pull down on, and bleed down that grid turn on + level that is continually
::being provided via R729 from the +100 V supply.
::
::
::The end result is the soaking up of the excess voltage via the 12B4 cluster and the regulation of the output buss down to the prescribed -150VDC.
::
::
::
::
:: Regulation Technique Summation:
::
::
::
::
::The left V712 triode's 1st grid receives a sample of the stable voltage reference.
::
::
::
::The right V712 triode's 1st grid receives a sample of a segment of of -105 V supply buss level.
::
::
::
::They compare . . . and any variance from the norm will result in a shifting up or down of the plate
::
::supply voltage of the right triode of V712.
::
::
::
::That potentially variant voltage then feeds over to the 1st grid of the V700 comparator stage, its
::potentially variant grid biasing swing could then provide for more or less conduction in accordance
::as to whether it was making a + swing or a - swing.
::
::
::That varying degree of conduction at the plate of V700 IS ALSO directly tied into the 1st grids of the 12B4 triodes.
::
::
::
::
::Net Result . . . . would then be:
::
::
::
::
::If V700 conducts more heavily, it pulls down the normal + grid bias present on those 12B4 stages via the R729 supply resistor from the +100VDC supply.
::
::
::As they conduct less, that trio starts absorbing more of the surplus voltage presence, thus the -105 buss has a reduced voltage level presence, with it then shifting down to the specified -105 level.
::
::
::Same control effect on the other situation of the -105 supply output being at LESS that its desired output voltage level.
::In that situation the V700 would be needing to conduct LESS in order for there to be less pull down of the static + bias being fed into the 12B4's 1st grids.
::
::
::
::
::How to do-it-to-it:
::
::
::
::
::DVM probe to chassis ground, and then you use its other probe to 2-4 or 7 of the 5651 . . if you then find an ~87 V presence, the gas tube is firing and regulating as it should .
::
::
::
::
::Move metering to the center terminal of R716 pot [ -150 supply adjust ] and swing the pot thru its range, to confirm an according voltage swing on the meter. . .if so.
::
::
::
::
::Move metering to the Pin #6 plate of V712, keep up the same swinging of the R716 thru its range to see if there is a like variable response in the swinging of that plate level.. . .if so.
::
::
::
::
::Move metering to the Pin #1 1 st grid of the V700 comparator stage plate to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
::
::
::
::
::
::Move metering to the Pin #7 of V725 1st grid to see if there is a like variable response in the swinging of that 1st grid voltage .. . .if so.
::
::
::
::
::
::NOW, you MOVE metering over to being across Pin #1 and pin #9 of V725 to see what the maximum voltage developed is, at the setting of the -150 adjustment pot which results in the highest voltage reading.
::
::
::If that is not high enough, that is why your raw B+ level is not being able to be adjusted down to that -105 standard level.
::
::
::Go back and check the screen, plate, first grid and cathode voltages of the V700 and check for their variance from the schematics estimation of those voltages.
::
::
::
::
::
::ZUJ'ing
::
::
::
::
::
::
::
::73's de Edd
::
::
::


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