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Mesa 440 Rocket high frequency noise generator machine
Hello gentlemen,
Been a while since I have worked on an amp that stumped me this much so here it goes. This amp makes noise in the preamp all the time on both channels basically a high pitched near the end of audible noise, the frequency changes when the channel is switched. The only place I could find noise with an oscilloscope in the preamp without the tubes installed is here:
https://drive.google.com/file/d/1Kxf...usp=share_link
In the power section after regulating to +/- 3v for the channel switching components of the amp. Of course this noise propagates all through the channel switching section. My question here: Since this is not strictly connected to the audio anywhere, was this section meant to be pure dc or is it ok that it has noise? If it's not ok, what components would you recommend testing/replacing to fix it?
Once I install V1 and V2, I have noise everywhere in the preamp. Here is an image of the noise appearing at the lead gain and rythm gain:
Strange part is, when I yank out V1, which is after V2 in the schematic, the noise goes away. Also, if I switch to rhythm channel the noise goes away to the oscilloscope, but returns when all tubes are installed and amp is on. All dc voltages on the tubes are about twice what they should be, IE 300 volts to plate and cathode is ~2vdc. This stays approximately the same regardless of how many tubes I have installed. Also I should mention that grid dc is 0 on all grids so nothing obvious with the coupling caps.
I am not super good at this, but my current theories are:
-That HV power supply noise is getting in somehow that I can't detect when tubes are out
-That the noise in the +/- 3vdc heater circuit for V1/V2 and footswitch circuit are somehow getting into the signal chain early, hence my inability to detect it when tubes are removed. Is this possible?
Someone throw me a bone here,
Been a while since I have worked on an amp that stumped me this much so here it goes. This amp makes noise in the preamp all the time on both channels basically a high pitched near the end of audible noise, the frequency changes when the channel is switched. The only place I could find noise with an oscilloscope in the preamp without the tubes installed is here:
https://drive.google.com/file/d/1Kxf...usp=share_link
In the power section after regulating to +/- 3v for the channel switching components of the amp. Of course this noise propagates all through the channel switching section. My question here: Since this is not strictly connected to the audio anywhere, was this section meant to be pure dc or is it ok that it has noise? If it's not ok, what components would you recommend testing/replacing to fix it?
Once I install V1 and V2, I have noise everywhere in the preamp. Here is an image of the noise appearing at the lead gain and rythm gain:
Strange part is, when I yank out V1, which is after V2 in the schematic, the noise goes away. Also, if I switch to rhythm channel the noise goes away to the oscilloscope, but returns when all tubes are installed and amp is on. All dc voltages on the tubes are about twice what they should be, IE 300 volts to plate and cathode is ~2vdc. This stays approximately the same regardless of how many tubes I have installed. Also I should mention that grid dc is 0 on all grids so nothing obvious with the coupling caps.
I am not super good at this, but my current theories are:
-That HV power supply noise is getting in somehow that I can't detect when tubes are out
-That the noise in the +/- 3vdc heater circuit for V1/V2 and footswitch circuit are somehow getting into the signal chain early, hence my inability to detect it when tubes are removed. Is this possible?
Someone throw me a bone here,
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