Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fossilshark on June 09, 2021, 06:23:43 pm

Title: p2p JCM800 build
Post by: fossilshark on June 09, 2021, 06:23:43 pm

Hi! I have posted a few questions about this amp in the past (been working on it over a year  :lipsrsealed: ) but I wanted to start an "official" thread for it. It is a point to point JCM800 2204 that I designed the layout and chassis and such myself. I am attaching the schematic in reference to my questions.

It was sounding sweet yesterday as i've been playing it while doing little tweaks on it for about a week now, but earlier I ziptied all the wires together and now I have to turn the amp all the way up to get volume on the high channel and the low channel has even less volume than that. Any ideas where to start?

Also any tips in general is appreciated, I am trying to get better at amp building as this is only my 3rd full tube p2p amp that I've completed.

Title: Re: p2p JCM800 build
Post by: fossilshark on June 09, 2021, 06:25:36 pm

schematic

Title: Re: p2p JCM800 build
Post by: sluckey on June 09, 2021, 07:22:43 pm

Quote from: fossilshark on June 09, 2021, 06:23:43 pm

...I ziptied all the wires together and now I have to turn the amp all the way up to get volume on the high channel and the low channel has even less volume than that. Any ideas where to start?

I would start by clipping zipties.

Title: Re: p2p JCM800 build
Post by: fossilshark on June 09, 2021, 08:45:09 pm

I unclipped alot of zipties around the tone stack and preamp section and found the 22k tone pot had an internal short, so I replaced that and now the high gain channel works but not the low gain

Title: Re: p2p JCM800 build
Post by: mresistor on June 10, 2021, 09:09:33 am

Seems to me the trouble would then be with the low input jack.