High-pitched squeal from amp - with gain and volume

Readings
On the triple cap, ohms setting
- red on top, black on bottom - -0- across the board
- black on bottom red on top - from left to right: -15.14 / -15.14 / -13.64

the stand alone cap in Plexi's pic out-take above (or between the triple cap and blue can cap below):
- red on top, black on bottom - -0-
Black on top - red on bottom: -13.54

IMG_20190512_201201.jpg
 
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RVA said:
Readings
On the triple cap, ohms setting
- red on top, black on bottom - -0- across the board
- black on bottom red on top - from left to right: -15.14 / -15.14 / -13.64

the stand alone cap in Plexi's pic out-take above (or between the triple cap and blue can cap below):
- red on top, black on bottom - -0-
Black on top - red on bottom: -13.54

View attachment 25081
Click to expand...
Bump. Do these readings indicate an issue?

Thanks
 
67plexi said:
Your amp is concerted a low plate 100k 1.5k 100k 1.5k low gain tap on the orange capacitors with the amp on don't get shocked.
My guess is your 12AX7 first tube close to the input. take your ohm meter and check the orange drop capacitors get a ohm reading then flip the leads
180 degrees and should read open or zero do this test power off it could be an oscillation issue. If you get a reading both sides you have a leaking capacitor.

Next would be voltage chart the amp

View attachment 25073
Click to expand...

RVA said:
Readings
On the triple cap, ohms setting
- red on top, black on bottom - -0- across the board
- black on bottom red on top - from left to right: -15.14 / -15.14 / -13.64

the stand alone cap in Plexi's pic out-take above (or between the triple cap and blue can cap below):
- red on top, black on bottom - -0-
Black on top - red on bottom: -13.54

View attachment 25081
Click to expand...

Looks like you don’t have any leaking capacitors in that area.(judging by your readings)

67plexi said:
I'm confused change the 12AX7 first input. #1 or V-1
Click to expand...

RVA said:
Bump. Do these readings indicate an issue?

Thanks
Click to expand...
 
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Did we establish whether the feedback is purely electronic within the amp, or vibration-induced via the speaker?
 
DonP said:
Did we establish whether the feedback is purely electronic within the amp, or vibration-induced via the speaker?
Click to expand...
I happens when I turn on the pedal on, with no guitar input source, and it starts immediately squealing. Does that help?
 
RVA said:
I happens when I turn on the pedal on, with no guitar input source, and it starts immediately squealing. Does that help?
Click to expand...

Not really. What needs to change is the physical relationship between amp and speaker. Either plug in an external speaker, or move it into the next room and shut the door. If the feedback is acoustic, moving the speaker should change it. Putting the speaker next door should stop it.
 
OK. I will use my longest cord on the external cab tonight and move it as far as I can. I will place a barrier in the way if possible. Thank you
 
Ray looking back I have had that issue only once with a ODS build and it was a 5751 tube that went crazy
The only other time was with a Trainwreck Express worked fine on my work bench but setting it on a 4/12" Marshall cabinet
the magnetic flux from the speakers I had to shield the chassis. Both chassis were aluminum not steel.

Next lead dress is important the pre amp does multiply the input signal one million times.

the carbon comp 2 watt resistor is the negative feedback loop what is the value I use a 4k7

The black velvet amp that SRV used on his first world tour 100 watt ODS Dumble had a trim pot on the negative feedback loop.

srvdumbonetb2.jpg
 
RVA said:
OK. I will use my longest cord on the external cab tonight and move it as far as I can. I will place a barrier in the way if possible. Thank you
Click to expand...



Or do you have different/other AMP/Speakers you can hook up the same rig,,,, pedals etc and see if it squeals in same room/different room etc too?
 
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RVA said:
V1. I also messed around with V3. In the end, neither made a difference
Click to expand...
Does this mean you swapped out all the preamp tubes and all the power tubes, one by one? We have to make sure that there are no defective tubes in the circuit.

Bypass any gizmo type of surge protectors. Plug amp directly into a house AC wall socket. Avoid connecting the buffered effects loop add-on for now. Only connect one pedal at a time. Don't use a power supply to power the pedal. Keep it at bare bones as possible to start off with!
 
Refresh my memory, RVA...
You bought the amp new?
Completely built by Ceriatone, and not a kit amp?
 
I sure wish we had a "send/bring me your amp" service here where all the best minds, diagnosticians and builders could all fix these issues lickity split, the only problem is most of us are many miles, KM's continents apart even. Heck 67 is practically in the USSR despite being a US citizen, and IVAN and Dave are Aussies, Grump is a Brit in Korea then of course we have Canadians throughout all the provinces, Kaliforneeans, Floor rid eans, and East coast USA folks like Bastard, Ray, and even a Kiwi.

I sure wish I could learn right in the presence of all you guys.
 
syscokid said:
Does this mean you swapped out all the preamp tubes and all the power tubes, one by one? We have to make sure that there are no defective tubes in the circuit.

Bypass any gizmo type of surge protectors. Plug amp directly into a house AC wall socket. Avoid connecting the buffered effects loop add-on for now. Only connect one pedal at a time. Don't use a power supply to power the pedal. Keep it at bare bones as possible to start off with!
Click to expand...
The amp is plugged into a Furman power conditioner. i would think that is better than the wall.

I swapped the pre-amp tubes separately (only 1 new tube at a time). The power tubes were not changed, but there was no obvious red-plating or anything
 
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