The Amp Garage

Yes, I guess I should have precised that the noise is only there when playing. Otherwise the amp is very quiet. No hiss or hum.

I tried the same guitar/cables with a different amp through a different cab and it's fine, so not coming from these.

RiR, if I any of the preamp tubes is out, how would I hear the issue? wouldn't the amp just be silent?

Unfortunately no, I don't.

Could it be a bad solder joint? I really don't think it's a wiring error nor a component value error. I have triple checked everything and measured all resistors.

I've never heard that type of screechy sound coming out of an amp before...

Nope...

Reversed the primaries and got the squeal of death.

Any suggestions where to look next?

Thanks Phil! I'll swap the primaries and report
back.

I hope that's it! No idea either where it could be coming from...

With all controls maxed out and jack in channel 1, measuring pin to ground:

V1.2 30K V2.2 715K V3.2 1M
V1.7 1M V2.7 230K V3.7 1M

If the OT primary were backwards, wouldn't I have gotten a howling sound first time I fired up the amp?

I meant I checked the grounding of the pots. Didn't see Xtian's post... You mean pins 2 and 7 (not 6)? Sorry, I haven't done this one before... With the amp off and controls on 0: Pin2 30K/235K/1M Pin 7 30K/530K/1M "The input to the amp also should have a good 1M reference on those (no pots there, j...

OK, I disconnected the NFB wire from the output jack and there is an improvement. It's not as choppy and the decay is not as strong. But it's still not sounding right. Again the sound almost has a fuzz/octave quality to it. Should I still swap the OT wires? I also noticed the mid and bass pots have ...

So... -Traced the whole circuit. -Checked continuity everywhere. -A couple of joint looked so so, redid them. -Moved/wiggled every pins Sounds exactly the same. With the guitar volume rolled down, the sound cleans up a tad but I still get that frying sound. It almost has a high octave quality to it....

I attached a clip of the noise it makes.

Lifted the coupling caps and measured for DC leakage and it's all good.

No DC on pots.

Ugh...

Thanks guys! Ill check and report back.

Right now I'm troubleshooting a new build. Ugh...

Finished a new build which is essentially a 1987 circuit with 6V6s. Only change is PI 820/22K. The (fixed) bias is fine and stable. No volume issue. B+ is around 390V on the 6V6s plates and screens. When I turn up the volume, the sound breaks up very early and gets into some nasty distortion... thin...

Hi, So I have a nice 67 100w blackflag with dual rectifier here. Had a bad case of ghosting... Changed all the caps while raising the filerting a bit (from 32uf to 47uf) except for the preamp. Ghosting is pretty much gone, can still hear it a bit when volume is on 8 but nothing unmanageable or too d...

My Deluxe seems to need some attention. The overdrive sounds pretty harsh, especially in the top end (not coming from the speaker). The amp has grid stoppers and screen resistors. Electros are new. In the PI, pin 6 has higher voltage than pin 1: 232v vs 229v, should be the other way around... Everyt...

Didit, what tweak would you have in mind?

For a pair of 34s or 66s, if I keep the B+ under 400V, would that be OK?

I have a JTM45 clone here which has around 440V on the plates. Should I check the cathode current to see where it's at... as a reference point?