Is the problem xfmr the one that is in between the 1st audio and the final push-pull audio?
Which tubes have no plate voltage? If it's the two final audio tubes, then their plate voltage doesn't go through the audio xfmr that feeds their grids, so I don't see that as your problem.
I'm not familiar with how you bypassed the open winding. But, whatever, you need to track down your voltage problem with a voltmeter.
Doug
:Hello all! I am working on a AK60. The audio driver transformer is half open on the secondary side, so I jumped it with a diagram in Langford-Smith I found on antiquewireless.org. The only audiable noise I get out of the speaker is when I move around the 27 tubes. There is no response by touching the grid caps on any of the 24s. The plate voltage on the tubes is around 3-4 volts, and it states that that should be around 160 or so. Could this still be the driver transformer causing this, or is there something else it could be. I have checked and replaced open resistors and the filter can caps. Thanks guys!
Hows about double-checking against info that you seem to have found out already.
Firstly, the bit of speaker noise that you have been able to acquire sort of seems to indicate full B+ level getting to the output tubes. Consult the mark-up schema at the bottom and confirm by DC voltage measurements…..initially… your main B+ line from
point [1] on the left over and up to the center tap [2] of the output transformer is complete.
Then concentrate on the sub B+ path at its origin point just to the right of the #1 point and then thru that second filter choke and coming out as Reference [A] and then on down the line to [B] to pass up and be voltage dropped by that 40K resistor above it [C] and then pass on up to that 65K late load resistor above and then [D] thru the RF choke and finally end up at the plate of the detector tube [E]…where you say that you only have a berry-berry paltry B+ level there. Or, problems in the respective dropping resistors, if a select tube voltage is low. As per your worrying about the open winding of the driver’s secondary, in the interim, the unit should still semi function working on one cylinder……. until the B+ voltage supply problem can be searched out. The series-stack derived output grid biasing loop is marked up on the magenta supply line, but also hold that ‘til later also. ZUJ’ing for your feedback.... Marked Up Schema Referencing:
Looking at the AF amp shows its supply getting routed from [F] and then thru 30K resistor and then it passes on up the power input terminal of your driver transformer.
Any connectivity problem along those supply lines could account for the abnormally low sub B+ level, with a problem between [1]
and [B], being at fault for both plates being low.
The last perspective to consider would be the voltage being pulled down by voltage leakage to ground loops thru marginal capacitors that are highlighted in the yellow mark up areas.
73's de Edd
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:Hows about double-checking against info that you seem to have found out already.
:
:Firstly, the bit of speaker noise that you have been able to acquire sort of seems to indicate full B+ level getting to the output tubes. Consult the mark-up schema at the bottom and confirm by DC voltage measurements…..initially… your main B+ line from
:point [1] on the left over and up to the center tap [2] of the output transformer is complete.
:
:
:Then concentrate on the sub B+ path at its origin point just to the right of the #1 point and then thru that second filter choke and coming out as Reference [A] and then on down the line to [B] to pass up and be voltage dropped by that 40K resistor above it [C] and then pass on up to that 65K late load resistor above and then [D] thru the RF choke and finally end up at the plate of the detector tube [E]…where you say that you only have a berry-berry paltry B+ level there.
:
:
:Looking at the AF amp shows its supply getting routed from [F] and then thru 30K resistor and then it passes on up the power input terminal of your driver transformer.
:
:Any connectivity problem along those supply lines could account for the abnormally low sub B+ level, with a problem between [1]
:and [B], being at fault for both plates being low.
:
: Or, problems in the respective dropping resistors, if a select tube voltage is low.
:
:The last perspective to consider would be the voltage being pulled down by voltage leakage to ground loops thru marginal capacitors that are highlighted in the yellow mark up areas.
:
:
:
:As per your worrying about the open winding of the driver’s secondary, in the interim, the unit should still semi function working on one cylinder……. until the B+ voltage supply problem can be searched out.
:
:
:
:The series-stack derived output grid biasing loop is marked up on the magenta supply line, but also hold that ‘til later also.
:
:
:
:ZUJ’ing for your feedback....
:
:
:
:Marked Up Schema Referencing:
:
:
:
:
:
:
:73's de Edd
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:
:
Edd- THank you for your advice. I cannot open or view the schematic you are referencing- could you email that to me? Then I can go from there! THanks again!
:
:
:
:
:
:
:
:
:Hows about double-checking against info that you seem to have found out already.
:
:Firstly, the bit of speaker noise that you have been able to acquire sort of seems to indicate full B+ level getting to the output tubes. Consult the mark-up schema at the bottom and confirm by DC voltage measurements…..initially… your main B+ line from
:point [1] on the left over and up to the center tap [2] of the output transformer is complete.
:
:
:Then concentrate on the sub B+ path at its origin point just to the right of the #1 point and then thru that second filter choke and coming out as Reference [A] and then on down the line to [B] to pass up and be voltage dropped by that 40K resistor above it [C] and then pass on up to that 65K late load resistor above and then [D] thru the RF choke and finally end up at the plate of the detector tube [E]…where you say that you only have a berry-berry paltry B+ level there.
:
:
:Looking at the AF amp shows its supply getting routed from [F] and then thru 30K resistor and then it passes on up the power input terminal of your driver transformer.
:
:Any connectivity problem along those supply lines could account for the abnormally low sub B+ level, with a problem between [1]
:and [B], being at fault for both plates being low.
:
: Or, problems in the respective dropping resistors, if a select tube voltage is low.
:
:The last perspective to consider would be the voltage being pulled down by voltage leakage to ground loops thru marginal capacitors that are highlighted in the yellow mark up areas.
:
:
:
:As per your worrying about the open winding of the driver’s secondary, in the interim, the unit should still semi function working on one cylinder……. until the B+ voltage supply problem can be searched out.
:
:
:
:The series-stack derived output grid biasing loop is marked up on the magenta supply line, but also hold that ‘til later also.
:
:
:
:ZUJ’ing for your feedback....
:
:
:
:Marked Up Schema Referencing:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
Edd- THank you for your advice. I cannot open or view the schematic you are referencing- could you email that to me? Then I can go from there! THanks again!
Never mind- it opened when I backed up and refreshed. Sorry!
:
:Is the problem xfmr the one that is in between the 1st audio and the final push-pull audio?
:
:Which tubes have no plate voltage? If it's the two final audio tubes, then their plate voltage doesn't go through the audio xfmr that feeds their grids, so I don't see that as your problem.
:
:I'm not familiar with how you bypassed the open winding. But, whatever, you need to track down your voltage problem with a voltmeter.
:Doug
:
:
::Hello all! I am working on a AK60. The audio driver transformer is half open on the secondary side, so I jumped it with a diagram in Langford-Smith I found on antiquewireless.org. The only audiable noise I get out of the speaker is when I move around the 27 tubes. There is no response by touching the grid caps on any of the 24s. The plate voltage on the tubes is around 3-4 volts, and it states that that should be around 160 or so. Could this still be the driver transformer causing this, or is there something else it could be. I have checked and replaced open resistors and the filter can caps. Thanks guys!
Thanks Doug- I will see what I can come up with based on your and Edd's advice. Thank you so much for your time.