sounds like the same issue i was having.  i learned my lesson.  resolder that fader's/pot's connections, whichever it is and see what that does.  if that doesn't get you any where i happen to know (thru the internet, not personally) a guy that worked for acoustic control corp.  i bet he could help you.  better hurry though.  he's pretty old and could croak at any moment.   xP  

I found the same model amp on ebay:  http://cgi.ebay.com/1990s-RMS-500RC-RMS_W0QQitemZ120118330641QQihZ002QQcategoryZ43375QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

The auction says 6" speakers.  They looked like 8" to me.

I thought it was strange because I connected a meter to the pot and it checked out fine no matter where I rotated it to.  In other words, it had a steady resistance when connected to the meter.  That didn't seem to be the case when the pot was in the amp.  Turning it from just past zero to full resulted in no signal except scratchiness and hum.  Had the pot been bad I'd think that the resistance would have fluctuated, indicating an intermittent connection.  I'm just glad it was an easy fix.  My buddy decided he didn't want the amp and said he would sell it for $25.  It doesn't sound very good to my ears but I might take it and experiment on it.  Watcha think?  It has two channels, probably 30-40 watts into two 8" speakers, spring reverb and a really crappy chorus (both footswitchable), crappy osb cabinet, and no real heatsink for the chips.  The heatsink is a flat piece of aluminum that runs the length of the chassis.  Sound wise it's in the neighborhood of an old Crate (yackkk!).  It might be something good to tinker around with.           

Just looking for any suggestions before I build one.....or two.....or three.   

I just want something to practice on and fiddle around with before my first tube amp build.  I think I'm going to build a little gem and a ruby.  What else is out there?  I had a danelectro honeytone a couple of years ago that sounded pretty raunchy, in a good way.  It died after a few weeks and I should have opened it up figured out how to fix it.  A friend of mine had one that was labeled as a fender bassman that sounded pretty good considering what it is.  I'm just prodding for variations, enclosure ideas, tried mods that any of you have liked, good part sources, etc.  I've ordered electronic parts from mostly mouser in the past.  I'd like to get the stuff local but radio shack's prices are completely rediculous.  I'm thinking about trying out futurelec because of the low prices.  Anyone tried them?  For enclosures I want to use something different.  Maybe an old jewelry box, a lunch box, a toy truck, etc.  Any ideas?             

Strange.  I pulled the pot and checked it's resistance and it checked out fine.  The low pot was the same value so i swapped the high and low to see if the problem followed.  It didn't and everything is working fine now.  The problem must have been a bad solder joint.  I guess I should have went over that pot's joints with a solder iron before pulling it.  Thanks again.   

Thanks guys.  I'm making a trip to radio shack today for a few things.  Hopefully I can find a suitable pot there.  I'll let you know how it turns out.

Hi.  First time posting here.  I found this forum looking for tips on troubleshooting a solid state guitar amp.  Hopefully someone here will be able to help me with this thing. 

A buddy of mine got a little 2x8 solid state guitar amp given to him but it has something wrong with it.  I tinker around with a lot of things so he dropped it off here hoping I could figure it out.  I really don't have a clue as to what's wrong with it.  It's an RMS500RC, made in Korea, 2x8" 2 channel amp with reverb and chorus.  I've never seen one before.  The problem is that when the 'high' knob is turned up, it starts crackling until about halfway thru the travel of the pot.  From half to full the amp just hums and there's no output other than the hum.  I took it apart and had a look around but didn't find any pcb cracks, bad joints, etc.  I did notice a burned plastic washer that goes between one of the ic's and it's mounting screw.  This amp has two TDA2030's mounted to the back of the chassis.  The burned washer (or insulator?) is white plastic.  That's the only sign of overheating that I could find.  All controls work good except this issue with the 'high' control.  Output to both speakers seems fine and output from the line outs seems fine. 

I recorded a sound clip by connecting one of the line out's to my sound card.  Maybe it will be helpful.  In the sound clip I flip on the amp, start playing some chords, and begin slowly turning up the high control from zero to halfway.  I'm strumming chords all along the way.  At 10 seconds you can hear the crackling starting.  At 36 seconds you can hear the humming.  I increased the volume of the humming to make it more apparent.  The hum is very apparent when running thru the amp's speakers but for some reason it's very low volume when using the line out's alone.  Sound clip is here (RMS500RC.mp3):  http://sellyoursoulformusic.googlepages.com/travis%27smp3%27s 

I can solder, I know how most components work and how to check them (except ic's), but I don't have a clue where to go from here.  If I fix, bonus for my buddy.  If I don't, bonus for me.  I'll have a complete chassis with a reverb tank and speakers for an amp project.