Here is the schematic:
http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
6J7 is the first audio amplifier. Remove the top connection and touch top of this tube. You will hear loud hum if audio circuits are working.
Electrolytics should be replaced. When bad they usually cause hum. They can also cause the radio not to operate due to low voltage. If shorted electrolytics can damage the rectifier tube (5Z4) and power transformer.
Norm
:I just bought a GE A-53 tombstone radio. The unit powers up and hums but does nothting else. Rubbing a little length of wire on the grid wire on the 6J7 produces faint crackling. Otherwise I'm getting nothing, not even crackling when I turn the volume control. I suspect the problem may begin with the electrolytics, but being new at this I'd like some advice.
:Also, the dial scale is a little warped and tends to rub up against the inside of the cabinet, which makes it bind. Would it be possible to place it in a low-heat oven between two weights and straighten it up that way?
:Thanks!
:Ken
Thanks, Norm. I will try touching the top of the 6J7 as you suggest and replace the electrolytics at the first opportunity. I'm very new at this, so I'm grateful the schematic also shows an under-chassis layout!
As for the dial scale, do you have any suggestions for that? The printing on it is still in good condition and I would hate to use a reproduction unless I absolutely have to.
Thanks,
Ken
Hi Norm,
I tried, or rather, had a friend touch the top of the 6J7. There was no sound emitted. Any ideas? Should I just begin with the electrolytics and recap the whole thing?
Thanks!
Ken
:Hi Ken
:
: Here is the schematic:
:
:http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
:
: 6J7 is the first audio amplifier. Remove the top connection and touch top of this tube. You will hear loud hum if audio circuits are working.
:
: Electrolytics should be replaced. When bad they usually cause hum. They can also cause the radio not to operate due to low voltage. If shorted electrolytics can damage the rectifier tube (5Z4) and power transformer.
:
:Norm
:
::I just bought a GE A-53 tombstone radio. The unit powers up and hums but does nothting else. Rubbing a little length of wire on the grid wire on the 6J7 produces faint crackling. Otherwise I'm getting nothing, not even crackling when I turn the volume control. I suspect the problem may begin with the electrolytics, but being new at this I'd like some advice.
::Also, the dial scale is a little warped and tends to rub up against the inside of the cabinet, which makes it bind. Would it be possible to place it in a low-heat oven between two weights and straighten it up that way?
::Thanks!
::Ken
Yes, electrolytic caps should be replaced in an older radio before much testing. If they short it will damage the rectifier tube and power transformer.
You may end up recapping the entire radio? If you do this replace one cap at a time. It's easy to connect one in wrong. Much harder to find a miswire than just repairing a defective component.
Pins #3 and #4 must be positive on a 6J7 tube. If either of these voltages are missing the stage won't operate.
Norm
:
:
:
:Hi Norm,
:I tried, or rather, had a friend touch the top of the 6J7. There was no sound emitted. Any ideas? Should I just begin with the electrolytics and recap the whole thing?
:Thanks!
:Ken
:
:
:
:
:
:
:
::Hi Ken
:
::
:: Here is the schematic:
::
::http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
::
:: 6J7 is the first audio amplifier. Remove the top connection and touch top of this tube. You will hear loud hum if audio circuits are working.
::
:: Electrolytics should be replaced. When bad they usually cause hum. They can also cause the radio not to operate due to low voltage. If shorted electrolytics can damage the rectifier tube (5Z4) and power transformer.
::
::Norm
::
:::I just bought a GE A-53 tombstone radio. The unit powers up and hums but does nothting else. Rubbing a little length of wire on the grid wire on the 6J7 produces faint crackling. Otherwise I'm getting nothing, not even crackling when I turn the volume control. I suspect the problem may begin with the electrolytics, but being new at this I'd like some advice.
:::Also, the dial scale is a little warped and tends to rub up against the inside of the cabinet, which makes it bind. Would it be possible to place it in a low-heat oven between two weights and straighten it up that way?
:::Thanks!
:::Ken