Bought used 12000 - Breakup WAY too early. Help?

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Tylenol Jones
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Bought used 12000 - Breakup WAY too early. Help?

Post by Tylenol Jones » Tue Apr 28, 2015 11:21 am

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.

Image

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?"

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VelvetGeorge
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Re: Bought used 12000 - Breakup WAY too early. Help?

Post by VelvetGeorge » Tue Apr 28, 2015 12:04 pm

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
Check out Plexi Replicas for my personal amp builds...
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neikeel
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Re: Bought used 12000 - Breakup WAY too early. Help?

Post by neikeel » Tue Apr 28, 2015 12:20 pm

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.
Neil

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Re: Bought used 12000 - Breakup WAY too early. Help?

Post by Tylenol Jones » Sat May 02, 2015 10:50 am

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

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Tylenol Jones
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Re: Bought used 12000 - Breakup WAY too early. Help?

Post by Tylenol Jones » Tue May 05, 2015 2:30 pm

Do these shots help at all?

Trying to figure this out with help from the experts. :)

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Re: Bought used 12000 - Breakup WAY too early. Help?

Post by ivan H » Tue May 05, 2015 5:28 pm

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

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Re: Bought used 12000 - Breakup WAY too early. Help?

Post by rockgod212 » Sun Jul 26, 2015 10:29 pm

that amp should sound absolutely killer like its set up, if you don't like it- just send it my way..... :what: :mrgreen:
"purple power rules"

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