Rockstah Modded 2203 Issues

[River City Studios]

Hey everyone,

This is my first post. Very cool to have access to this forum. Much appreciated.

I live in BFE (Fresno, CA) and there are no quality amp techs in the area that I know of. As a result, every time I have a problem with an amp, I have to ship it to someone, which increases the cost of the repair significantly. I have sent stuff to Voodoo in NY. Trace does great work, but shipping to and from is $300. So, I thought I would figure out how to repair my amps, at least fix simple problems, myself. The guys at "Rigtalk" said this was a good place to start. I know how to use a soldering iron and I have built pedal kits and small electronic components before, so I am not too afraid of jumping (of course, I know about discharging the caps).

All that being said, this is my current problem:

I have a 77' Marshall 2203 that was modified by Mark Abrahamian for a buddy of his. Here is a link to the MetroAmp Mark started when he finished the build back in early 2010: http://forum.metroamp.com/viewtopic.php?f=16&t=29776" onclick="window.open(this.href);return false;

I bought it from "Rick". The biggest problem is after about 30 minutes of playing, I notice what I can best describe as a "crackling" sound when I play lower notes and let them ring out, especially bar chords. A low F works best at producing the "crackling". Other issue, which is less annoying but annoying just the same, is that the amp is noisy, I.E. has a minor hum when off bypass. It's very faint, but it is still their. Something else that is kind of strange is that when I connect a tuner to the tuner out on a volume pedal in my chain, the amp hum gets louder.

I have done the obvious things, I.E. changed the tubes multiple times, cleaned the tube sockets, pots, and jacks, etc. Made no difference.

I started reading through the forum and thought changing the filter and bias caps might help, but when I checked the amp, I noticed Mark had recapped it with F&T's. I'm sure they could still be failing, but I thought it unlikely.

I took it to the local guy, who said it was fixed when my wife picked it up for me (big mistake) but when I got it home, it sounded the same. I actually don't think he even touched it.

Any suggestions as to what the problem might be? Any guidance would be appreciated. If I had a direction to look in, I could do the research and figure out how to fix it myself, hopefully.

If I can't fix it myself, maybe I'll just sell it.

Thanks in advance,

--Dan S.

[ezs]

Post what local guy did. Sounds like a cold solder joint somewhere, or an intermittent thermal condition? Well nows a good time to get to know your amp.

[RACKSYSTEMS]

Could be ocillation. I would be happy to look at it for you. Your close at least. Or sort of.