RCA RT2500 Buzzing Sound - Replace 6800uv 16v caps

It is more than likely a capacitor or two on the power supply. I would replace the power supply or the capacitors on the PSU board if you are comfortable with a soldering iron, flux and desoldering braid/ vacuum pump.
When I replace the caps I always get a slightly higher voltage and ensure I get 105° rated caps. If possible find some low ripple capacitors. Typically if they are 16V 1000uf I will replace with 25V 1000uf 105°.

Make sure all your audio jacks are hooked up right and make sure your on a good mode of sound. Also, you can try this for support from the actual RCA service. http://voxrightnow.custhelp.com/cgi-bin/voxrightnow.cfg/php/enduser/ask.php?p_sid=wOSZIMUi&p_accessibility=0&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PWRmbHQmcF9ncmlkc29ydD0mcF9yb3dfY250PTcmcF9wcm9kcz0xNTgmcF9jYXRzPTAmcF9wdj0xLjE1OCZwX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX25sJnBfc2NmX2JyYW5kPSZwX3BhZ2U9MQ**&p_srch=1

they are 12000uf 63v

You can use a higher voltage capacitors without problems its the value of uf that should remain the same. But sometimes you can use a higher uf like a 330uf can be replaced with 470uf but never go lower than the original value on uf and voltage. But you can safely use 6800uf 25v or 35v.

Similar problem here, at first 20-30 min warm-up time, followed by irregularity in sound levels, to a complete failure after using for around 30 minutes after warm up (choppy sound to a steady buzz). I wonder if over heating has something to do with it since I left it on all the time after the need of a warm-up occurred. One night, a horrid buzz came from the system and ever since it would become unbearable to listen too after a few minutes, I am debating either to attempt a fix or chunk it. I haven't tried the caps and fuses yet, but seeing your problem leads me to believe it is something more to the problem, and more likely a better investment would be an upgrade.

Hey EmperorBob, was reading a short across D119 & D120. pulled (I think it was) C139 and was able to get a good reading across the two diodes. reading a short on the cap (out of circuit). Still poking around. Will let you know if I find anthing else...

I'd suspect your power supply capacitors are on their last leg. replace them.  - This was posted by videoguy1742. :   this problem is CURED simply by replacing 2 capacitors inside on the main board. They are easily identified by a bulge on the top end of the capacitors. The capacitors are located between the heat sinks. The size is 6800uf/16v.
I am a RadioShack dealer and sold a few of these in 2000/2001. I bought one for myself. I have repaired only 2 that had the same problem as listed by HAGUC above. They both are working great and for the record. . .are NOT peices of JUNK,. . .hehe. . .they just need a little TLC. Parts available from larger electronics parts houses, not at RadioShack

It sounds like a capacitor in the power supply is just about to die. With the power disconnected have a look at the large tin can looking gizmos near the power transformer. There could be a couple of them. Leave the unit switched off for a while before going near them they could still pack a splat. Replace them with the same value and make sure they're connected the right way and it should solve your problem. Whilst in there have a good look for any other smaller capacitors which look as if they're getting rounded at the top. Replace them too. Either that or dig deep and buy a new one.

i have the same system that i bought new and after about 3 yaers it did the same thing for no reason. i think you get what you paid for!!!