Pin 5 EL34 -DC voltage reading

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Janglin_Jack
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Pin 5 EL34 -DC voltage reading

Post by Janglin_Jack » Sat Oct 01, 2022 7:28 pm

It has been a long time since I have built an amp. I have a completed 50w 1987 project amp that was completed but never tested. It got put in storage and I just got it back (long story). I started to go through the testing steps and I have the 3 preamp tubes in and no power tubes, (SS rectifier). When I test for -DC voltage on pin 5 of the power tube sockets, I get almost -400v DC. The test steps say I should be seeing closer to -50vDC. My bias supply is coming off the standby switch and connects to a 220K resistor. Nothing seems to happen when I rotate the bias pot either. Feels like something is wrong. Is my bias supply wired correctly with this value resistor?

Mike

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Janglin_Jack
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Re: Pin 5 EL34 -DC voltage reading

Post by Janglin_Jack » Sat Oct 01, 2022 8:19 pm

I suppose I should just delete this post, but maybe it will be helpful for someone as a reminder. My bias network didn't have a ground connection!!! Soldered in a ground wire and now getting ~-50DCV on pin 5. Resuming testing... :shock:

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axeman
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Re: Pin 5 EL34 -DC voltage reading

Post by axeman » Tue Nov 01, 2022 4:42 pm

Send me some detailed photos so I can help you.
Axeman6@msn.com

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