Marshall 2203 REEEEEEEEEEE-work

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harddriver
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by harddriver »

Maybe it's a type of parasitic oscillation. Take a look at those JEL layouts I sent you and try a 470pf ceramic or mica cap on V2A's 100K plate resistor and see it dampens/attenuates out the noise.

Was the noise always there since you fired the amp up or did it just start???
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by PLX »

harddriver wrote: Sun Jul 31, 2022 11:10 pm Maybe it's a type of parasitic oscillation. Take a look at those JEL layouts I sent you and try a 470pf ceramic or mica cap on V2A's 100K plate resistor and see it dampens/attenuates out the noise.

Was the noise always there since you fired the amp up or did it just start???
I'll try that.

This is a totally new noise after the recent REEEEEEEEEEEEEEEE-work of this amp.
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by lll »

Possibility exists you have an iffy can cap (filter)?
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by PLX »

lll wrote: Mon Aug 01, 2022 12:13 am Possibility exists you have an iffy can cap (filter)?
Maybe, but I just replaced all 3 with brand new filter caps.
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by harddriver »

PLX wrote: Sun Jul 31, 2022 11:31 pm
harddriver wrote: Sun Jul 31, 2022 11:10 pm Maybe it's a type of parasitic oscillation. Take a look at those JEL layouts I sent you and try a 470pf ceramic or mica cap on V2A's 100K plate resistor and see it dampens/attenuates out the noise.

Was the noise always there since you fired the amp up or did it just start???
I'll try that.

This is a totally new noise after the recent REEEEEEEEEEEEEEEE-work of this amp.
So the noise was there immediately on the first fire up from the REEEEEEEEEEEEEEEEEEEWORK? Yes.... :?

I would do the filter caps before putting that 470 pf plate snubber on as you may solve the problem with the caps.

I agree with III............I think it may be a faulty filter cap, maybe swap them out for one of the old 50/50uf LCR that you know are good one at a time and give the amp a listen. Maybe the ESR leakage is poor on one of them causing the noise, because if you noticed in video the guy seems to reference that the intermodulation noise was due to the poor connection and or leaky filter cap.

They may be new but they may be leaky.

I would swap the preamp cap out first then listen and play the amp. If the noise is still there, then replace the preamp with the new F/T and then move that LCR 50/50uf cap to the screens and do the exact same thing, play and listen if the noise is still there then replace with the new F/T and move to the Mains................. Capish????????? 8-)

That amp doesn't have enough gain really to need the 100K 470pf plate snubber but It's a tool to try to narrow things down if it isn't the new F/T caps.
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by PLX »

Thanks guys :!:

Based on the advice in this thread from HD and LLL, I replaced the 50µF/50µF filter cap on the pre-amp taps, and the 1MΩ audio taper pots on the PRE AMP and MASTER VOLUME controls and that fucking noise is gone !

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Re: Marshall 2203 REEEEEEEEEEE-work

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PLX wrote: Thu Aug 18, 2022 12:35 am Thanks guys :!:

Based on the advice in this thread from HD and LLL, I replaced the 50µF/50µF filter cap on the pre-amp taps, and the 1MΩ audio taper pots on the PRE AMP and MASTER VOLUME controls and that fucking noise is gone !

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I'm guessing when the master and preamp pots grounded out to your buss wire the carbon tracks on the wipers arced over burning them. The other was the possibility that the 10 year old 50/50 uf on the preamp was having issues as III recommended. 8-) AND OR BOTH ISSUES!
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by PLX »

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Re: Marshall 2203 REEEEEEEEEEE-work

Post by harddriver »

Sounds great PLX! The love the clank on the muted upstrokes!

After playing it some more the noise is still gone? Just making sure............... ;)
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Re: Marshall 2203 REEEEEEEEEEE-work

Post by PLX »

harddriver wrote: Thu Aug 18, 2022 1:57 pm Sounds great PLX! The love the clank on the muted upstrokes!

After playing it some more the noise is still gone? Just making sure............... ;)
The only noise now is from my rusty, ham-fisted playing.

That reminds me of the time I used to play in a wedding band named "Rusty Ham Fist".

:|
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