I am working on a National TV-7 7 inch electrostatic deflection TV. Everything now works, but I cannot center the raster. I have checked the voltage divider networks that supply the bias voltages to the plates and have replaced any resistors that were out of tolerance. There are two 0.005 ufd, 5000 V caps that feed the deflection signals to the plates, and isolate the high voltage on the centering network from the deflection circuitry. They are originals. If they were leaky, could they interfere with the balance of the bias network?
Lou
Anybody have a few units to sell? I am having some trouble finding that high a voltage rating.
0.005 uF, 6Kv
Thanks for any help in advance!!
The units that are in there now are wax paper types (huge!!!!)
Lou
:That fixed static DC voltage is establishing the base location of the beam positioning, with the cumulative sweep signal filling in the screens display pattern.
:Don't know if they were using other than ceramic types for that application, but ceramic is all that I would expect to be reliable longterm.
:If my situation, I would already have one cap unit out, and with one end connected to as high of a DC voltage to 5KV level as available and the other lead to the + lead of a VTVM or modern DVM, either....having their minumal loading characteristics.... then not be happy til I saw the initial cap charging surge drop waaaaay down to the MV...uv! levels.hi hi.
:73's de Edd
:
:Thanks Guys
:
:Anybody have a few units to sell? I am having some trouble finding that high a voltage rating.
:
:0.005 uF, 6Kv
:
:Thanks for any help in advance!!
:
:The units that are in there now are wax paper types (huge!!!!)
:
:Lou
::That fixed static DC voltage is establishing the base location of the beam positioning, with the cumulative sweep signal filling in the screens display pattern.
::Don't know if they were using other than ceramic types for that application, but ceramic is all that I would expect to be reliable longterm.
::If my situation, I would already have one cap unit out, and with one end connected to as high of a DC voltage to 5KV level as available and the other lead to the + lead of a VTVM or modern DVM, either....having their minumal loading characteristics.... then not be happy til I saw the initial cap charging surge drop waaaaay down to the MV...uv! levels.hi hi.
::73's de Edd
::
Since it is a resistor bridge, i.e. each set of plates ( horiz set, vert set )gets a fixed bias, changes in HV level (within reason) should not affect the position of the beam, only changes in One Side of the bridge should affect the beam centering. The same principle is used on older oscilloscopes.
Lou
:How is the centering accomplished on that set? Is there some kind od DC bias applied to the plates for that purpose? Perhaps the bias supply has an issue?
:
:
::Thanks Guys
::
::Anybody have a few units to sell? I am having some trouble finding that high a voltage rating.
::
::0.005 uF, 6Kv
::
::Thanks for any help in advance!!
::
::The units that are in there now are wax paper types (huge!!!!)
::
::Lou
:::That fixed static DC voltage is establishing the base location of the beam positioning, with the cumulative sweep signal filling in the screens display pattern.
:::Don't know if they were using other than ceramic types for that application, but ceramic is all that I would expect to be reliable longterm.
:::If my situation, I would already have one cap unit out, and with one end connected to as high of a DC voltage to 5KV level as available and the other lead to the + lead of a VTVM or modern DVM, either....having their minumal loading characteristics.... then not be happy til I saw the initial cap charging surge drop waaaaay down to the MV...uv! levels.hi hi.
:::73's de Edd
:::
BUT, don't stop looking if you feel you have the time.
I appreciate it - this is the last thing on this set that doesn't work.
Lou
::The bias for the bridge that supplies the plates of the CRT comes directly from the HV for the tube.
::
::Since it is a resistor bridge, i.e. each set of plates ( horiz set, vert set )gets a fixed bias, changes in HV level (within reason) should not affect the position of the beam, only changes in One Side of the bridge should affect the beam centering. The same principle is used on older oscilloscopes.
::
::Lou
::
:::How is the centering accomplished on that set? Is there some kind od DC bias applied to the plates for that purpose? Perhaps the bias supply has an issue?
:::
:::
::::Thanks Guys
::::
::::Anybody have a few units to sell? I am having some trouble finding that high a voltage rating.
::::
::::0.005 uF, 6Kv
::::
::::Thanks for any help in advance!!
::::
::::The units that are in there now are wax paper types (huge!!!!)
::::
::::Lou
:::::That fixed static DC voltage is establishing the base location of the beam positioning, with the cumulative sweep signal filling in the screens display pattern.
:::::Don't know if they were using other than ceramic types for that application, but ceramic is all that I would expect to be reliable longterm.
:::::If my situation, I would already have one cap unit out, and with one end connected to as high of a DC voltage to 5KV level as available and the other lead to the + lead of a VTVM or modern DVM, either....having their minumal loading characteristics.... then not be happy til I saw the initial cap charging surge drop waaaaay down to the MV...uv! levels.hi hi.
:::::73's de Edd::::
:Hi Lou
: Well Antique Electronic Supply has a 2,500Pf at 10,000 Volt, you could get four of them parallel 2 of them to get 5,000PF and the other 2 to get the other 5,000pf which equals out to .005uf & .005uf at 10,000 volt, I'll do some more checking in the mean time, but that would be your best bet right now, they are $1.22 each.
:Mark
Lou
::Well, I did find a site that has no minimum - gonna call them tomorrow. 1-800-272-2737.
::
::BUT, don't stop looking if you feel you have the time.
::I appreciate it - this is the last thing on this set that doesn't work.
::
::Lou
::
::::The bias for the bridge that supplies the plates of the CRT comes directly from the HV for the tube.
::::
::::Since it is a resistor bridge, i.e. each set of plates ( horiz set, vert set )gets a fixed bias, changes in HV level (within reason) should not affect the position of the beam, only changes in One Side of the bridge should affect the beam centering. The same principle is used on older oscilloscopes.
::::
::::Lou
::::
:::::How is the centering accomplished on that set? Is there some kind od DC bias applied to the plates for that purpose? Perhaps the bias supply has an issue?
:::::
:::::
::::::Thanks Guys
::::::
::::::Anybody have a few units to sell? I am having some trouble finding that high a voltage rating.
::::::
::::::0.005 uF, 6Kv
::::::
::::::Thanks for any help in advance!!
::::::
::::::The units that are in there now are wax paper types (huge!!!!)
::::::
::::::Lou
:::::::That fixed static DC voltage is establishing the base location of the beam positioning, with the cumulative sweep signal filling in the screens display pattern.
:::::::Don't know if they were using other than ceramic types for that application, but ceramic is all that I would expect to be reliable longterm.
:::::::If my situation, I would already have one cap unit out, and with one end connected to as high of a DC voltage to 5KV level as available and the other lead to the + lead of a VTVM or modern DVM, either....having their minumal loading characteristics.... then not be happy til I saw the initial cap charging surge drop waaaaay down to the MV...uv! levels.hi hi.
:::::::73's de Edd::::
:::Hi Lou
::: Well Antique Electronic Supply has a 2,500Pf at 10,000 Volt, you could get four of them parallel 2 of them to get 5,000PF and the other 2 to get the other 5,000pf which equals out to .005uf & .005uf at 10,000 volt, I'll do some more checking in the mean time, but that would be your best bet right now, they are $1.22 each.
:::Mark
:Hi Lou
: I found another place you can check, Just Radios, they have some on EBay right now, 3 .0047uf 6000V buy it now price for $7.99
:Mark
I was looking thru my stash and knew that I had some HV ceramic units that I had used in the fabrication of a HV ...no, make that .. HIGH VOLTAGE multiplier circuit, but was unsure of remembering their exact capacitance. A search found them to be of .001 @ 25KV. They should merely idle in your less demanding application. I had Hi-potted them up to even greater than that specification and was only experiencing static / stray microvolt levels in testing.
Sooooo.... I have them available for your use and have pulled out 10 of them. A single unit measures about 3/8 in dia by the same in depth, with radial leads and a glass hard, thick red epoxy conformal coating 5 in parallel should be using less real estate than
one of the previous paper ones found in the unit.
I am asking some where in between nil and zilch for them, should you not have already comitted yourself on a (shudder...big BUX) order to a supplier....forward your snail mail addee to eddw35....at....comcast.net.
You had been on this sets problems before, but I thought that you had it nailed, so I never had gone to the effort of pulling its schema out from archrchival "cold storage".
A further touchpoint on analysis:
You made no comeback on the mentioned DC leakage test of a unit.
To make further meaningful evaluation, I might suggest the tuning of the Tee Wee in to a stationary video pattern, e.g. a test pattern (nearly impossible to find)...a fixed bulletin board on a cable or satellite signal , outputted as a tunable / accessible Ch3 RF signal, to that receivers tuner, or lastly the fixed video pattern of a DVD player with its printing (propaganda) displayed in its blue screens
background. Typically it outputs a raw video signal so that would have to be inputted into a Vee Cee Ruhhh to then obtain a TV-7 cabable Ch 3 tuned RF signal from the VCR's Ch 3 RF output.
When that info is displayed, make dimensional notes of exactly where the patterns edges lay in reference to kine screen edge.
Then inter-swap your two capacitors and see if there is a great variance of the pattern position. This would let you know if one capacitor is more at fault in the trouble than the other. Ideally, if there was minumal patttern shifting, we could ascertain that there was negligible differences in any presence of DC leakage, as well as the units almost being equal in their capacitive value.
73's de Edd
The ones I want are 0.005 uF , 5 Kv.
Good idea on the patter - do have a patter generator that could do the job.
Thanks
Lou
:A mentioned parts sourcing of .....Centerpoint Electronics???
:
:I was looking thru my stash and knew that I had some HV ceramic units that I had used in the fabrication of a HV ...no, make that .. HIGH VOLTAGE multiplier circuit, but was unsure of remembering their exact capacitance. A search found them to be of .001 @ 25KV. They should merely idle in your less demanding application. I had Hi-potted them up to even greater than that specification and was only experiencing static / stray microvolt levels in testing.
:Sooooo.... I have them available for your use and have pulled out 10 of them. A single unit measures about 3/8 in dia by the same in depth, with radial leads and a glass hard, thick red epoxy conformal coating 5 in parallel should be using less real estate than
:one of the previous paper ones found in the unit.
:I am asking some where in between nil and zilch for them, should you not have already comitted yourself on a (shudder...big BUX) order to a supplier....forward your snail mail addee to eddw35....at....comcast.net.
:
:You had been on this sets problems before, but I thought that you had it nailed, so I never had gone to the effort of pulling its schema out from archrchival "cold storage".
:
:A further touchpoint on analysis:
:You made no comeback on the mentioned DC leakage test of a unit.
:To make further meaningful evaluation, I might suggest the tuning of the Tee Wee in to a stationary video pattern, e.g. a test pattern (nearly impossible to find)...a fixed bulletin board on a cable or satellite signal , outputted as a tunable / accessible Ch3 RF signal, to that receivers tuner, or lastly the fixed video pattern of a DVD player with its printing (propaganda) displayed in its blue screens
:background. Typically it outputs a raw video signal so that would have to be inputted into a Vee Cee Ruhhh to then obtain a TV-7 cabable Ch 3 tuned RF signal from the VCR's Ch 3 RF output.
:When that info is displayed, make dimensional notes of exactly where the patterns edges lay in reference to kine screen edge.
:Then inter-swap your two capacitors and see if there is a great variance of the pattern position. This would let you know if one capacitor is more at fault in the trouble than the other. Ideally, if there was minumal patttern shifting, we could ascertain that there was negligible differences in any presence of DC leakage, as well as the units almost being equal in their capacitive value.
:
:73's de Edd
:
Understood....did you not read the pulled 10 of them for you...10 to make 2 replacement caps.
e.g. 5 parallel .001's gives your wanted value of .005 ufd and the 25Kv rating should be highly desirable.
25KV....???
Physical Example:
You are a 105 lb gymnast and have to do a flip and be caught overhead by your partner.
You have a choice of that partner.... you have one that struggles to maintain a wobbly composure
on a 125 lb catch, OR another which you have seen adeptly doing a catch of 250 lbs. Wouldn't the
latter be your better choice ?
As for the multiple caps...you are going to be additively and dimutively modulating that static voltage with the sweep sawtooth waveform at 15,734 Khz, and that is into the threshold that the repetitive
hammering of that waveform into the capacitors results in a bit of heat being created. Multiple units can
spread that undesirable trait amongst the units. Paper units having worse characteristics than ceramic in their ESR at those freqs.
Example:
I frequently run into solid state switch mode power supply designs that experience a failure mode in the
same manner, however they are pulses that are run on up into the 60-200khz freq spectrum and the
capacitor type in that case is a 105 deg C electrolytic.
The cumulative heat results in the capacitor slowly...yet progressively venting out a bit of its
internal damp electrolyte as a gas and with an exponentially, warmer operation of the cap. That being, up to the point where it really runs hot and pressurizes up to the point of venting / spewing
/exploding from the alum case thru a weakened top expansion crease.
When one experiences this situation it can be avoided again by the mere use of two parallel electrolytics,
whereupon an initial design center point operation
resulted in it being merely warm to the fingertip
, could then be dimished down to the barely perceptible temperature threshold.
73's de Edd
I went to JustRadios and ordered the proper caps for this, but I do thank you for your offer.
Hopefully, with new electrolytics, new 5000 pf caps and a new CRT ( I substituted a Radar CRT , 7JP7 for the 7JP4, and it works perfectly)I can watch this set for some time to come!!!!
Lou
:"The ones I want are 0.005 uF , 5 Kv"
:
:Understood....did you not read the pulled 10 of them for you...10 to make 2 replacement caps.
:e.g. 5 parallel .001's gives your wanted value of .005 ufd and the 25Kv rating should be highly desirable.
:
:25KV....???
:Physical Example:
:You are a 105 lb gymnast and have to do a flip and be caught overhead by your partner.
:You have a choice of that partner.... you have one that struggles to maintain a wobbly composure
:on a 125 lb catch, OR another which you have seen adeptly doing a catch of 250 lbs. Wouldn't the
:latter be your better choice ?
:As for the multiple caps...you are going to be additively and dimutively modulating that static voltage with the sweep sawtooth waveform at 15,734 Khz, and that is into the threshold that the repetitive
:hammering of that waveform into the capacitors results in a bit of heat being created. Multiple units can
:spread that undesirable trait amongst the units. Paper units having worse characteristics than ceramic in their ESR at those freqs.
:Example:
:I frequently run into solid state switch mode power supply designs that experience a failure mode in the
:same manner, however they are pulses that are run on up into the 60-200khz freq spectrum and the
:capacitor type in that case is a 105 deg C electrolytic.
:The cumulative heat results in the capacitor slowly...yet progressively venting out a bit of its
:internal damp electrolyte as a gas and with an exponentially, warmer operation of the cap. That being, up to the point where it really runs hot and pressurizes up to the point of venting / spewing
:/exploding from the alum case thru a weakened top expansion crease.
:When one experiences this situation it can be avoided again by the mere use of two parallel electrolytics,
:whereupon an initial design center point operation
:resulted in it being merely warm to the fingertip
:, could then be dimished down to the barely perceptible temperature threshold.
:73's de Edd
: