Bought used 12000 - Breakup WAY too early. Help?

[Tylenol Jones]

It was assembled by the seller. Here's what it came with.

****** trannies
NOS Iskra resistors
NOS mustard caps (almost everywhere)
SoZo caps for the rest
PEC PPIMV (post-master volume)
New production Svetlana EL34 tubes.

For now, this is the only image of the build I have... until I get to open it up once I'm home.



MV is halway, volume is at *1* and there's tons of breakup already! I was under the impression that it should start to break up at noon.

It's my first Marshall-style amp so I'm quite green at this. What could be causing it to be this "hot?"

[VelvetGeorge]

Most likely culprits to breaking up that early will be the bright cap and the negative feedback resistor value.

Can we identify those? Hard to tell from the pic.

george

[neikeel]

Yes need better pics.
It has that big electrolytic cap on V2a that can just give you mud on some amps.
I cannot see a bright cap.
Just get blur when looking a the NFB resistor and cannot see which cap it goes to.

[Tylenol Jones]

As promised, here are shots of the circuitry. If there is a need for any other specific shots, please let me know.

[Tylenol Jones]

Do these shots help at all?

Trying to figure this out with help from the experts.

[ivan H]

Hi, I notice that the V1b cathode has an 820r/.68uf combination (which Marshall did use on early split cathode amps). U might try changing that resistor to a 2k7, & get rid of the electrolytic on the V2a cathode. I cant see the value of this cap but I'll bet its larger than the .68uf that was used here. Cheres

[rockgod212]

that amp should sound absolutely killer like its set up, if you don't like it- just send it my way.....