lowe opta "vineta" type 1790w

7/26/2009 9:37:01 PMPaul Knaack

Hello all, I am hoping somebody could help me with this German radio. tubes are ecc85, ech81, ef85, eabc80, ECL82,ECL82. The cathode resistor (2000 ohm)on the last ECL82 power tube gets hot and smokes after about 45 seconds. swapped power tubes around no difference, both tubes test good, no shorts, all electrolytic caps replaced. radio plays. also i temporarily substituted an ef80 for the ef85 although I don't think this has anything to do with it.Much thanks for any help. Paul

7/26/2009 9:53:27 PMNorm Leal

Hi Paul

Most likely not a tube problem but rather lack of grid bias on the output stage. Measure voltage between grid #1 and cathode on your output tube. Grid #1 must be about 16 volts negative. If not the tube will draw too much current causing cathode resistor to overheat.

http://tdsl.duncanamps.com/show.php?des=ECL82

Norm

:Hello all, I am hoping somebody could help me with this German radio. tubes are ecc85, ech81, ef85, eabc80, ECL82,ECL82. The cathode resistor (2000 ohm)on the last ECL82 power tube gets hot and smokes after about 45 seconds. swapped power tubes around no difference, both tubes test good, no shorts, all electrolytic caps replaced. radio plays. also i temporarily substituted an ef80 for the ef85 although I don't think this has anything to do with it.Much thanks for any help. Paul
:

7/26/2009 9:55:53 PMNorm Leal

Hi Paul

One other thing, a cathode resistor should be lower value than 2,000 ohms. Maybe 400 ohms?

Norm

:Hi Paul
:
: Most likely not a tube problem but rather lack of grid bias on the output stage. Measure voltage between grid #1 and cathode on your output tube. Grid #1 must be about 16 volts negative. If not the tube will draw too much current causing cathode resistor to overheat.
:
:http://tdsl.duncanamps.com/show.php?des=ECL82
:
:Norm
:
::Hello all, I am hoping somebody could help me with this German radio. tubes are ecc85, ech81, ef85, eabc80, ECL82,ECL82. The cathode resistor (2000 ohm)on the last ECL82 power tube gets hot and smokes after about 45 seconds. swapped power tubes around no difference, both tubes test good, no shorts, all electrolytic caps replaced. radio plays. also i temporarily substituted an ef80 for the ef85 although I don't think this has anything to do with it.Much thanks for any help. Paul
::
:

7/27/2009 4:17:09 PMPaul Knaack

:Hi Paul
:
: One other thing, a cathode resistor should be lower value than 2,000 ohms. Maybe 400 ohms?
:
:Norm
:
::Hi Paul
::
:: Most likely not a tube problem but rather lack of grid bias on the output stage. Measure voltage between grid #1 and cathode on your output tube. Grid #1 must be about 16 volts negative. If not the tube will draw too much current causing cathode resistor to overheat.
::
::http://tdsl.duncanamps.com/show.php?des=ECL82
::
::Norm
::
:

7/28/2009 11:25:00 AMNorm Leal

Hi Paul

A 2000 ohm resistor is reasonable for the triode section. Since this section of the tube draws little current the resistor shouldn't burn unless grid #1 is positive. Check the coupling cap from previous stage. It may be leaky or shorted?

Norm

::Hi Paul
::
:: One other thing, a cathode resistor should be lower value than 2,000 ohms. Maybe 400 ohms?
::
::Norm
::
:::Hi Paul
:::
::: Most likely not a tube problem but rather lack of grid bias on the output stage. Measure voltage between grid #1 and cathode on your output tube. Grid #1 must be about 16 volts negative. If not the tube will draw too much current causing cathode resistor to overheat.
:::
:::http://tdsl.duncanamps.com/show.php?des=ECL82
:::
:::Norm
:Hello, thanks for the reply. First off I should have let you know that the resistor goes from pin 8 (cathode of the triode section)to B-. 2k is what it reads on the schematic and is what was in place. voltage from pin 1 to pin 8 is -122vdc voltage from pin 2 to pin 3 is -14 vdc. thank you, you have helped me many times just by my reading your relpys for other people. Paul
:
:::
::
:

7/28/2009 9:06:52 PMPaul Knaack

:Hello, My next question is, there were two paper caps left between af and output stage.I didn't change them right away because they have a third lead coming out of them going to b- and I am not sure what to do with them.Any suggestions, please? They are both .02mfd. they are testing at about .06mfd. I removed one leg from each one and jumped a new .02 over them but no change yet.Would a bad coupling cap cause both output tubes the same problems? (only problem on one)Thanks for your help, Paul :Hi Paul
:
: A 2000 ohm resistor is reasonable for the triode section. Since this section of the tube draws little current the resistor shouldn't burn unless grid #1 is positive. Check the coupling cap from previous stage. It may be leaky or shorted?
:
:Norm
:
:::Hi Paul
:::
::: One other thing, a cathode resistor should be lower value than 2,000 ohms. Maybe 400 ohms?
:::
:::Norm
:::
::::Hi Paul
::::
:::: Most likely not a tube problem but rather lack of grid bias on the output stage. Measure voltage between grid #1 and cathode on your output tube. Grid #1 must be about 16 volts negative. If not the tube will draw too much current causing cathode resistor to overheat.
::::
::::http://tdsl.duncanamps.com/show.php?des=ECL82
::::
::::Norm
::Hello, thanks for the reply. First off I should have let you know that the resistor goes from pin 8 (cathode of the triode section)to B-. 2k is what it reads on the schematic and is what was in place. voltage from pin 1 to pin 8 is -122vdc voltage from pin 2 to pin 3 is -14 vdc. thank you, you have helped me many times just by my reading your relpys for other people. Paul
::
::::
:::
::
:

7/29/2009 12:55:44 AMNorm Leal

Hi Paul

A leaky couping cap will cause grid #1 of one tube to go positive. If you have one leaky cap most likely there are more.

An open grid resistor could also cause the problem.

A tube will draw too much current when grid #1 starts going positive. This can cause a cathode resistor to burn if enough current is available. Measure voltage across the 2K resistor. With proper bias there will only be a couple volts across this resistor.

A positive grid should be the only thing causing a cathode resistor to burn unless a tube is shorted.

Third lead on those caps may be a grounded shield? You can use standard caps but keep leads short and mount them near the chassis if possible. Since I don't have the schematic going by what usually is in a radio.

Norm

::Hello, My next question is, there were two paper caps left between af and output stage.I didn't change them right away because they have a third lead coming out of them going to b- and I am not sure what to do with them.Any suggestions, please? They are both .02mfd. they are testing at about .06mfd. I removed one leg from each one and jumped a new .02 over them but no change yet.Would a bad coupling cap cause both output tubes the same problems? (only problem on one)Thanks for your help, Paul :Hi Paul
::
:: A 2000 ohm resistor is reasonable for the triode section. Since this section of the tube draws little current the resistor shouldn't burn unless grid #1 is positive. Check the coupling cap from previous stage. It may be leaky or shorted?
::
::Norm
::
::::Hi Paul
::::
:::: One other thing, a cathode resistor should be lower value than 2,000 ohms. Maybe 400 ohms?
::::
::::Norm
::::
:::::Hi Paul
:::::
::::: Most likely not a tube problem but rather lack of grid bias on the output stage. Measure voltage between grid #1 and cathode on your output tube. Grid #1 must be about 16 volts negative. If not the tube will draw too much current causing cathode resistor to overheat.
:::::
:::::http://tdsl.duncanamps.com/show.php?des=ECL82
:::::
:::::Norm
:::Hello, thanks for the reply. First off I should have let you know that the resistor goes from pin 8 (cathode of the triode section)to B-. 2k is what it reads on the schematic and is what was in place. voltage from pin 1 to pin 8 is -122vdc voltage from pin 2 to pin 3 is -14 vdc. thank you, you have helped me many times just by my reading your relpys for other people. Paul
:::
:::::
::::
:::
::
:

7/30/2009 6:04:23 AMEdd

SIR Paul. . . . .and it does look like you DO have the Knaack

I initially looked thru this topic and then consulted my 20-40 Loews schematics and saw that I had NOTHING utilizing that

ECL 82. . .( . . .aka . . . our AMERIKANSKI. . .6 “ B ig Mama ” 8) . . .tube, in its circuit design. . . much less, with the
utilization of

a Push-Pull pair, in which case, they probably must be using the triode section(s) as the phase inverter function to drive the

output pentodes.

I did read back and forth on the comments and observations already made and condensed down to this, highlighting its main

info points being provided:

CONDENSED INFO:

What I then did instead, was to pull out this amp circuit that is using an ECL82 Push Pull circuit and did some mark up
and highlighting of its like points of interest.

Initially, note that the selection of the cathode resistors values of the output pair has set the neg grid bias up in the vicinity
of ~21 Vdc, whereas the typically lower values found would have been bringing that bias value down.

In THIS circuit, they are shifting on up towards a class AB biasing parameter.

THEN, what you need to see is that with the circuits 820 ohm value for the phase inverter pair, the produced negative biasing there is in the order of -2VDC, so you might expect in the order of almost double that, plus a bit more, for your units 2 k value of a shared cathode resistor.
[ Not that 120+ volts ! . . . . instead, with its resultant cathode current being limited by the phase inverters plate load resistors value.]

I highlighted all of this circuits coupling capacitors in orange, but with the outputs set now being of less suspicion.

I do interpret your subbing in of the extra .O2’s, as being in series with the old ones right ? as shunting across the
units would still have any series DC leakage being still present thru a bad unit.

BUTTTTT what you really need to do is compare this circuit to your situation, and see if you have the C3 capacitor
equivalent bad in your unit.

My preferred capacitance leakage test manner is to lift the lead of the coupling capacitor that is opposite of the plate
connection and use 2 clip leads and connect the positive meter lead of your + DVM to the lifted, resultant floating lead,
and the other metering - lead then goes to ground.

Then, you power up the set and take a third test lead and have one end connected to ground and use its free end to
short the tested cap / + meter lead node to ground . That action need take but a few seconds. That then lets the cap
take on a full charging IMMEDIATELY. Otherwise, you would be w a i t i n g , if you were dependent upon
the High Z charging loop being presented thru your meters HIGH input impedance. You then note what voltage develops
on your metering. If its above mere decades of millivolts, that cap needs chunked and replaced.

Move on to the AF coupling capacitors "C10 and C11" next to see what shape they really are in. If they are bad , my choice to replace the shielded type of construction is to use a flat disc ceramic capacitors rated at 500-1KV, with the lead lengths selected so that the 1st grid connection wire gets almost zero lead length .

That’s it for any more info now. . . .unless you can additionally provide us a copy of that LOEW units’ schematic for
us here, or else, via E-mail.

73's de Edd

P/P ECL82 Push Pull Circuitry INFO:

8/1/2009 3:12:13 PMPaul Knaack

Hi, I double checked my cathode voltages. Please tell me what I am doing wrong. I put dvom on dc volts, put neg lead on pin 8 (cathode of triode section of ecl82), positive lead on pin 1 (grid of triode), I then read about - 125 vdc also this time i am getting sparks and arcing around pin 7(grid2 of pentode) so now I am going to replace this tube socket also when I replaced the .02 coupling caps I did disconnect the old ones. I may be overlooking something were circuits go through the switches for the band switching buttons. All resistors test fine.
:
: A leaky couping cap will cause grid #1 of one tube to go positive. If you have one leaky cap most likely there are more.
:
: An open grid resistor could also cause the problem.
:
: A tube will draw too much current when grid #1 starts going positive. This can cause a cathode resistor to burn if enough current is available. Measure voltage across the 2K resistor. With proper bias there will only be a couple volts across this resistor.
:
: A positive grid should be the only thing causing a cathode resistor to burn unless a tube is shorted.
:
: Third lead on those caps may be a grounded shield? You can use standard caps but keep leads short and mount them near the chassis if possible. Since I don't have the schematic going by what usually is in a radio.
:
:Norm
:
:::Hello, My next question is, there were two paper caps left between af and output stage.I didn't change them right away because they have a third lead coming out of them going to b- and I am not sure what to do with them.Any suggestions, please? They are both .02mfd. they are testing at about .06mfd. I removed one leg from each one and jumped a new .02 over them but no change yet.Would a bad coupling cap cause both output tubes the same problems? (only problem on one)Thanks for your help, Paul :Hi Paul
:::
::: A 2000 ohm resistor is reasonable for the triode section. Since this section of the tube draws little current the resistor shouldn't burn unless grid #1 is positive. Check the coupling cap from previous stage. It may be leaky or shorted?
:::
:::Norm
:::
:::::Hi Paul
:::::
::::: One other thing, a cathode resistor should be lower value than 2,000 ohms. Maybe 400 ohms?
:::::
:::::Norm
:::::
::::::Hi Paul
::::::
:::::: Most likely not a tube problem but rather lack of grid bias on the output stage. Measure voltage between grid #1 and cathode on your output tube. Grid #1 must be about 16 volts negative. If not the tube will draw too much current causing cathode resistor to overheat.
::::::
::::::http://tdsl.duncanamps.com/show.php?des=ECL82
::::::
::::::Norm
::::Hello, thanks for the reply. First off I should have let you know that the resistor goes from pin 8 (cathode of the triode section)to B-. 2k is what it reads on the schematic and is what was in place. voltage from pin 1 to pin 8 is -122vdc voltage from pin 2 to pin 3 is -14 vdc. thank you, you have helped me many times just by my reading your relpys for other people. Paul
::::
::::::
:::::
::::
:::
::
:

8/1/2009 4:59:43 PMPaul Knaack

Hi, I replaced tube socket, powered it up and crossed my fingers, with volt meter hooked to pins 8 and 1 . radio came to life, voltage reading -1.15 vdc checked grid voltage on pentode -18.5 vdc. My tube manual say's 0 volts on triode grid and -16 on pentode grid. so do I still have a problem? or is this close enough? Many thanks to Norm and Edd. Paul

8/1/2009 5:31:30 PMEduardo Eugenio Emelio Arredando Arenales Catalan von Gonzalez de la Garza IV

AAhhhhhhh Sooooooo, methinks that you have just been introduced to, as well as having had your first encounter, with a "carbonized" intereletrode leakage path on a tube socket.

If you have the BIG bucks, for steatite, porcelain or ceramic you might as well spring for 2 socket and replace its companion '82 socket as well.

Your read out specs sound OK to me now, and it sounds like you are now definitely closer to a "GO Dog Go" status on your set now !. . . .and alas, I had just about reformatted, cleaned up, bleached and re-digitized that tattered, yellowed, schema of yours using the latest NASA transposing, bit rate averaging and sampling resupposition techniques. . . .oh well.

73's de edd

:Hi, I replaced tube socket, powered it up and crossed my fingers, with volt meter hooked to pins 8 and 1 . radio came to life, voltage reading -1.15 vdc checked grid voltage on pentode -18.5 vdc. My tube manual say's 0 volts on triode grid and -16 on pentode grid. so do I still have a problem? or is this close enough? Many thanks to Norm and Edd. Paul
:

8/1/2009 6:52:44 PMNorm Leal

Hi Paul

Close enough. You are most likely using a meter that doesn't load down the circuit as much. You won't have a problem with those grid voltages.

Norm

8/1/2009 8:31:59 PMPaul Knaack

:Hi, I've been playing it for the last few hours now and all seems well other than certain bass notes seem to really thump. I was reading an article on American vs European de-emphasis and apparently this radio has a 50usec de-emphasis and the US has a 75msec de-emphasis and that is what causes the thumping bass. Were is this de-emphasis circuit located and how do I correct it? Thanks Again,Paul

8/2/2009 2:00:43 PMEdd

Sir Paul . . .

I was away from all of my Info archives at the time of my last posting, but have full acess to them now.

Now, if you want to change your sets FM output circitry in order to comform with our US FM standards, just
consult the attached Thumbnail of the circuitry involved.

One needs to stretch this sets designed time constant of its de-emphasis filter in its R-C elements from the
current produced 50 us , on out to a 75 us time constant.

Take note of the larger marked in [RED] node at the FM detector output circuitry . The placement of 150 pf of
capacitance to ground will just shift the circuits R-C characteristics downwards, to respond to a new
~2125 hz cut off frequency and then have an~ 6 db shift for each decade away from that frequency.

A silver mica type of capacitor would be a very stable capacitor to use.

The [GREEN DOT] plotting signifies your AM circuitry detectors output audio routing.

The [ RED DOT ] plotting signifies your FM circuitry detectors output audio routing.

The provided mark up is as good as I was able to retrieve from converting from a J-peg file to an ever so
more flexible bit map format.

The J-peg is just horrible about solorizing and all of the accompanying small random pixel background clutter.

All in all, I think that you will now be happy with the performance of an old ~57 vintage product.

73's de Edd

Loew's FM De-emphasis filter Mark-up Thumbnail:

8/2/2009 8:53:07 PMPaul Knaack

:
:
:
:
:
:Sir Paul . . .
:
:
:
:
:I was away from all of my Info archives at the time of my last posting, but have full acess to them now.
:
:Now, if you want to change your sets FM output circitry in order to comform with our US FM standards, just
:consult the attached Thumbnail of the circuitry involved.
:
:
:One needs to stretch this sets designed time constant of its de-emphasis filter in its R-C elements from the
:current produced 50 us , on out to a 75 us time constant.
:
:
:Take note of the larger marked in [RED] node at the FM detector output circuitry . The placement of 150 pf of
:capacitance to ground will just shift the circuits R-C characteristics downwards, to respond to a new
:~2125 hz cut off frequency and then have an~ 6 db shift for each decade away from that frequency.
:
:A silver mica type of capacitor would be a very stable capacitor to use.
:
:
:The [GREEN DOT] plotting signifies your AM circuitry detectors output audio routing.
:
:The [ RED DOT ] plotting signifies your FM circuitry detectors output audio routing.
:
:
:
:The provided mark up is as good as I was able to retrieve from converting from a J-peg file to an ever so
:more flexible bit map format.
:
:The J-peg is just horrible about solorizing and all of the accompanying small random pixel background clutter.
:
:
:
:All in all, I think that you will now be happy with the performance of an old ~57 vintage product.
:
:
:
:
:
:
:
:
:
:73's de Edd
:
:Hi Edd, Thanks Again for all your help, Radio sounds great as is if I don't turn the bass up too high, so I am going to give this a try, should only get better
: Paul
:

:

:
:
:

:Loew's FM De-emphasis filter Mark-up Thumbnail:
:
:

:
:
:
:
:

:
:
:

8/9/2009 10:45:32 PMPaul Knaack

::
::
::
::
::
::Sir Paul . . .
::
::
::
::
::I was away from all of my Info archives at the time of my last posting, but have full acess to them now.
::
::Now, if you want to change your sets FM output circitry in order to comform with our US FM standards, just
::consult the attached Thumbnail of the circuitry involved.
::
::
::One needs to stretch this sets designed time constant of its de-emphasis filter in its R-C elements from the
::current produced 50 us , on out to a 75 us time constant.
::
::
::Take note of the larger marked in [RED] node at the FM detector output circuitry . The placement of 150 pf of
::capacitance to ground will just shift the circuits R-C characteristics downwards, to respond to a new
::~2125 hz cut off frequency and then have an~ 6 db shift for each decade away from that frequency.
::
::A silver mica type of capacitor would be a very stable capacitor to use.
::
::
::The [GREEN DOT] plotting signifies your AM circuitry detectors output audio routing.
::
::The [ RED DOT ] plotting signifies your FM circuitry detectors output audio routing.
::
::
::
::The provided mark up is as good as I was able to retrieve from converting from a J-peg file to an ever so
::more flexible bit map format.
::
::The J-peg is just horrible about solorizing and all of the accompanying small random pixel background clutter.
::
::
::
::All in all, I think that you will now be happy with the performance of an old ~57 vintage product.
::
::
::
::
::
::
::
::
::
::73's de Edd
::
::Hi Edd, Thanks Again for all your help, Radio sounds great as is if I don't turn the bass up too high, so I am going to give this a try, should only get better
:: Paul
::

::

::
::
::

::Loew's FM De-emphasis filter Mark-up Thumbnail:
::
::

::
:: Just want to let you know I made the changes to the de-emphasis, the German radio now sounds wunderbar regardless how much bass is put to it.Thanks for all your help. Paul
::
::
::

::
::
::
:

8/10/2009 8:00:22 AMEdd

:::

:::
:::
:::
:::
:::
:::Sir Paul . . .
:::
:::
:::
:::
:::I was away from all of my Info archives at the time of my last posting, but have full acess to them now.
:::
:::Now, if you want to change your sets FM output circitry in order to comform with our US FM standards, just
:::consult the attached Thumbnail of the circuitry involved.
:::
:::
:::One needs to stretch this sets designed time constant of its de-emphasis filter in its R-C elements from the
:::current produced 50 us , on out to a 75 us time constant.
:::
:::
:::Take note of the larger marked in [RED] node at the FM detector output circuitry . The placement of 150 pf of
:::capacitance to ground will just shift the circuits R-C characteristics downwards, to respond to a new
:::~2125 hz cut off frequency and then have an~ 6 db shift for each decade away from that frequency.
:::
:::A silver mica type of capacitor would be a very stable capacitor to use.
:::
:::
:::The [GREEN DOT] plotting signifies your AM circuitry detectors output audio routing.
:::
:::The [ RED DOT ] plotting signifies your FM circuitry detectors output audio routing.
:::
:::
:::
:::The provided mark up is as good as I was able to retrieve from converting from a J-peg file to an ever so
:::more flexible bit map format.
:::
:::The J-peg is just horrible about solorizing and all of the accompanying small random pixel background clutter.
:::
:::
:::
:::All in all, I think that you will now be happy with the performance of an old ~57 vintage product.
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::Hi Edd, Thanks Again for all your help, Radio sounds great as is if I don't turn the bass up too high, so I am going to give this a try, should only get better
::: Paul
:::

:::

:::
:::
:::

:::Loew's FM De-emphasis filter Mark-up Thumbnail:
:::
:::

:::
::: Just want to let you know I made the changes to the de-emphasis, the German radio now sounds wunderbar regardless how much bass is put to it.Thanks for all your help. Paul
:::
:::
:::

:::

Sir Paaul. . . .

I knew that. . .

I had your Telefunken Gavotte 7 on my Samuels pull list while out at the archival storage at " the mule barn" this weekend, but I just now read that you seem to have it already.

Don't know the significance of your models export aspect , you designated , excepting the power supply and your
acquaintance with the FM aspect... . IF it FM's.

My mistake now. . . .I see that it was Adam Cee that was temporarily short of that schematic.

73's de Edd