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Hi guys,
Been working on this nice little cathedral. I've changed the filter caps (but not the caps in the blocks), a couple of resistors, and have it powering up. All I'm getting is a soft hum now. I have a suspicion the oscillator coil isn't working. However, I'm wondering about the caps in the blocks. What do you guys think....caps or coil...or something els?. What's a good test on the osc. coil? Tubes test strong.
Thanks,
Art
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(03-23-2012, 10:04 PM)Art Hoch Wrote: Hi guys,
Been working on this nice little cathedral. I've changed the filter caps (but not the caps in the blocks), a couple of resistors, and have it powering up. All I'm getting is a soft hum now. I have a suspicion the oscillator coil isn't working. However, I'm wondering about the caps in the blocks. What do you guys think....caps or coil...or something els?. What's a good test on the osc. coil? Tubes test strong.
Got to do it all and the resistors.
Terry
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Do you or any friends have a scope? With it you can quickly see if the oscillator is working.
It's very important to measure the plate and screen voltages before you do anything.
Pete
Pete AI2V
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Do you or any friends have a scope? With it you can quickly see if the oscillator is working.
It's very important to measure the plate and screen voltages before you do anything.
Pete
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No, no scope.
I have already removed two (not simultaneously) of the capacitor blocks filled with tar and am soldering back the connections on the second one (7625SU). Kind of messy because even though I have read how to the the tar out "easily," (
http://www.philcorepairbench.com/capbuild.htm), (step 4--fig.4) is not working for me, and I have had to melt the tar to empty the block.
Along the way, I found resistor 22 listed in the parts list with a value of 24K but in the schematic it is 240K. And to beat that, the resistor in the radio actually was a 420K which tested @ 393K. So I have a conundrum: which should it be????????????????
Art
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Do you or any friends have a scope? With it you can quickly see if the oscillator is working.
It's very important to measure the plate and screen voltages before you do anything.
Pete
*********************
No, no scope.
I have already removed two (not simultaneously) of the capacitor blocks filled with tar and am soldering back the connections on the second one (7625SU). Kind of messy because even though I have read how to the the tar out "easily," (
http://www.philcorepairbench.com/capbuild.htm), (step 4--fig.4) is not working for me, and I have had to melt the tar to empty the block.
Along the way, I found resistor 22 listed in the parts list with a value of 24K but in the schematic it is 240K. And to beat that, the resistor in the radio actually was a 420K which tested @ 393K. So I have a conundrum: which should it be????????????????
Art
[/quote]
Please post schematic or post to schematic. Probably you can answer your own question.
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It may have been another production run or code than that of the schematic you have, they changed many things as a radio was produced as to repair issues that would come up.
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(03-27-2012, 10:31 PM)tab10672 Wrote: It may have been another production run or code than that of the schematic you have, they changed many things as a radio was produced as to repair issues that would come up.
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True. I'm going with a 240K resistor.
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Radio has all new caps and resistors replaced if out-of-tolerance. However, radio not playing yet ---- and a wire-wound 325 ohm resistor (#30 on schem) connected to transformer gets VERY hot. Is this a sign of a bad transformer?
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No I don't think so. Check the polarity of the filter caps. Sounds like you've got one in backwards. How much juice you got from the chassis to the filament of the 80 tube?
Terry
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Thanks to Terry's help with the oscillator coil, this little cathedral is playing like a champ w/lots of bass from the speaker.
It's missing the little lug tap on the sensitiviy control on the back of the chassis. Does anyone have a spare they could send me? Right now I have it "bushed" up and held with a very small tap but suspect it might be losing some reception from that rigging.
Thanks in advance if you can help.
Art
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It's missing the little lug tap on the sensitiviy control on the back of the chassis. Does anyone have a spare they could send me? Right now I have it "bushed" up and held with a very small tap but suspect it might be losing some reception from that rigging.
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Thanks to Terry (again) for supplying the lug tap. I appreciate you very much.
Art
