Different Hot rod deluxe

[nosaj]

New tube tried in v2 no change on noise. Want to ay PCB is 2002 version. Will check resistor in jet switching circuit to verify what's there.
pull out the scope tonight an see if I can find where noise starts.

Thanks ,
Nosaj

[nosaj]

Verified this pcb has the diode cr16 in the jfet switching section.
Because I don't have a computer in my work space I'm trying to map out some areas for noise. Looking at the schematic I'm looking at c5,c6, and c7 checking for DC Leakage and if the noise were before that the controls would affect them in my thinking. open to any other suggestions on probing.

Thanks,
Nosaj

[Jazz P Bass]

"Noise on both channels."

"V2 ground pin2 kills some noise ground pin7 all noise gone."

Something does not add up.
The Cl & Dr channels split off at V2A/ C2.
Two separate circuits.
Why would grounding V2A/ pin 7 have any affect on the Clean channel noise.
Or does it not?

[nosaj]

Ok Grounding pin7 kills noise on Drive channel if I chang the channel with it still grounded the clean channel gets noisy.

thanks,
nosaj

[Jazz P Bass]

Well, that makes less sense.
I would lift C8 to get all of the Jfet stuff out of the loop.
After that, replace R16 & / or C2.

[SoulFetish]

Well, that makes less sense.
I would lift C8 toget all of the Jfet stuff out of the loop.
After that, replaced R16 & / or C2.

Yeah, so far I tend to agree with this. I've definitely had plate resistors go noisy in these and fail outright as well.
Do you have any.. lets say 0.1-0.47µF/630V caps handy? If so, you can make a probe where you connect one side to ground, and use the other lead to AC ground the other nodes.
If you can put the probe on the plate (pin one) of V2a, you can see if the noise goes away. Or you can replace it all together and see if that fixes it as well, but I suspect this plate resistor might be the culprit too, like Jazz says.

[nosaj]

Yeah, so far I tend to agree with this. I've definitely had plate resistors go noisy in these and fail outright as well.
Do you have any.. lets say 0.1-0.47µF/630V caps handy? If so, you can make a probe where you connect one side to ground, and use the other lead to AC ground the other nodes.
If you can put the probe on the plate (pin one) of V2a, you can see if the noise goes away. Or you can replace it all together and see if that fixes it as well, but I suspect this plate resistor might be the culprit too, like Jazz says.

Ok did this an it quieted noised down a bit but not all. Lifting c8 no change. So I pulled board to replace the plate resistors r16 r22 and what do you know I saw a little black spot looked like dirt or something at first but noooo it was a track that had arced over. Cleaned the carbon up replaced the plate resistors for good measure put it back together . What do ya know. Sounds as it should now.

Thanks so much guys.
nosaj

[bsco]

Yeah...it doesn't take much to cause problems.....I like the idea in post 21....will have to try that out......