Static in reverb channel of '74 Deluxe Reverb

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Randy Magee
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Static in reverb channel of '74 Deluxe Reverb

Post by Randy Magee »

I have a weird static in the reverb channel of a '74 Deluxe Reverb that I can't seem to track down. Someone else worked on this amp before it came to me and left off the cathode bypass cap for the reverb driver tube. I replaced that cap as well as the 2.2K resistor associated with it, but that didn't solve the problem. The voltages on that 12AT7 driver tube check out. The board on this amp is warped pretty badly and I did find the board conductive in the area that the driver circuit resides. I measured 2.1 volts DC straight off the board. Would that be enough to cause static in the reverb. The amp sounds fine when the reverb is off and the normal channel is fine as well.
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xtian
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Re: Static in reverb channel of '74 Deluxe Reverb

Post by xtian »

Randy Magee wrote: Mon Jul 10, 2017 10:44 pmI measured 2.1 volts DC straight off the board. Would that be enough to cause static in the reverb.
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jjman
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Re: Static in reverb channel of '74 Deluxe Reverb

Post by jjman »

My '71 had board conduction where the 5 leads join that include the wire to the V4A grid. Faint crackling. I added a standoff to float that node off the board. Pressing the vicinity with a chopstick revealed it. (I modded the values of the 10pf/3.3meg to 47pf/1meg for more signal.)
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Re: Static in reverb channel of '74 Deluxe Reverb

Post by Stevem »

yup , conductive board there!

I just had a SR reissue circuit board type that arc internal to the board in the PI section such that I had to cut out a whole section of the board and point to point wire it!
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Randy Magee
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Re: Static in reverb channel of '74 Deluxe Reverb

Post by Randy Magee »

I ended up replacing the board with a black G10 garolite board and the issue is resolved and should never reappear...
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Stevem
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Re: Static in reverb channel of '74 Deluxe Reverb

Post by Stevem »

Good to hear, pun intended!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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