Most likely you need to re-solder the power tube sockets.
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Sizzling & Crackling in HR Deville Problem
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wire across it.
So by design, putting in a 1 ohm resistor, allows TP30 to measure the plate current. Why then does the schematic state TP30 in mV?
I agree with g1, resolder all the pins on the power tube sockets. I don't care how good they appear to be.Education is what you're left with after you have forgotten what you have learned.
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Originally posted by Perkinsman View PostPOWER AMP IN jack, turn it down-Noise still present
PREAMP OUT jack to some other amp-Noise still present in Deville, not other amp speaker
edit: since you said the reverb level doesn't affect the noise I would guess it isn't the power amp in jack, as anything that happens at the jack goes straight into the reverb circuit.Last edited by glebert; 11-17-2019, 08:42 AM.
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Originally posted by glebert View PostSo this seems to narrow it down to the power amp section, or possibly the effects loop jacks/circuit. I would pull the PI tube and see if the noise persists. If there is still noise with no PI tube it has to be the power tubes. If the noise goes away it narrows it down to the loop jacks or the PI. I hate the 9 pin PCB jacks that they use on these, they are quite fragile internally and sometimes they behave like they need a good cleaning yet cleaning doesn't help. You could do a bridge past the power amp in jack pretty easily to rule it out.
edit: since you said the reverb level doesn't affect the noise I would guess it isn't the power amp in jack, as anything that happens at the jack goes straight into the reverb circuit.
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I noticed some "cap stuff" on one of the caps C34 and it's only measuring 10.5V. If I'mreading the schematic correctly, it should be up over 450. Is it appropriate to change out just one cap if it's bad? Also, why are they rated at 350v when the voltages are much higher, wouldn't 500v be more appropriate?- Own Opinions Only -
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I will add that the IC branded capacitors in modern Fender amps are notoriously famous for causing a range of problems. When I worked at a Fender authorized shop and needed to call support, it was the first thing they often said, "did you change those caps?"It's weird, because it WAS working fine.....
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I have seen problems with the 82K and 100K PI plate resistors so often in the Hot Rod/Blues Deluxe/DeVille series I automatically change them in every amp I see.
With the PI pulled out the noise disappears because there is no DC current though the resistors, I suggest using 1 Watt resistors for their higher breakdown voltage spec.
Symptoms are: crackling when they start to break down, distortion when they go open.
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Good point, could be 2 separate issues, solder joints on power tube sockets causing bias problems/redplate, and PI plate resistors making crackling.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by Helmholtz View PostThe voltage divider R72/73 takes care that with good caps the DCV across C34 is 50% of the voltage at point Z, i.e. about 240VDC. If it's much lower C34 is leaky and must be replaced. What is the Z voltage?
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Originally posted by g1 View PostGood point, could be 2 separate issues, solder joints on power tube sockets causing bias problems/redplate, and PI plate resistors making crackling.
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SP = solder post, or something like that. Look at the schematic, they are simply places on the board to connect the wires from the choke, which is not on the board itself. Look at the parts layout drawing, or for that matter look on your board to where the choke wires go, SP is probably silk screened on the board.
I see that point Z is at the intersection of R72 & R74 & whatever SP2 means but they don't actually connect on the top of the board that I see so is point Z on the + side of C33 or C34?Education is what you're left with after you have forgotten what you have learned.
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