Crown PowerBase 1 slight buzz

[MuseChaser]

I'm never sure whether to post requests for repair insight in the solid-state forum or here in the DIY forum. Hope I chose wisely...

I have the aforementioned amp, purchased new back in the 80s, and it has served me long, hard, and very well, six nights a week for several of those years, without a hiccup, powering a pair of Yamaha 4115H, and then as we downsized a bit a pair of 3115H speakers. I'm at the point now in my career where I don't play the kind of music that needs that much power, nor do I have the desire to carry a lot of big, heavy gear like I did when I was a kid and more was better.

Anyway, I listed the amp and the 3115H speakers on our local CL, but before doing so plugged it all in for the first time in probably five years just to make sure it was all good. There's a VERY slight buzz in one channel, and it follows the leads when swapping speakers, so it's definitely the amp. It's not noticeable far away from the speakers, nor close up when anything is being played, but it is there. I disclosed this in the ad I posted, and I'm afraid it's discouraging folks from inquiring. I'd like to fix it.

I have a DMM, signal generator app, and a 'scope, with beginning knowledge in the use of the 'scope, having used it to successfully diagnose and repair (with the help of folks here @Ray Gianelli @ConradH and a few kind others) a Dynaco SCA80Q and a Trace Elliott Acoustic Cube amp. I do not have the repair manual for the amp. Can anyone point me to probable causes or initial places to start looking?

Thanks in advance.

 

[Lavane]

If it was in both channels I would start with the power supply, but it isn't.
I'm not familiar with that amp, but it doesn't have a dual power supply by chance does it? My first thought is since its been sitting so long, and with the age of it, it could be an electrolytic capacitor going south. Sometimes capacitors can reform over time. I've used my variac to slowly bring up older equipment, SS and tube, over a few hours time to let the caps reform. Sometimes it works. But being that old and used quite a bit over the time you've had it, its probably time for a recap anyway. Does it have gain controls like other Crown amps? I had a Sony power amp that made noise in one channel that was due to a dirty gain pot. Using a scope to trace the signal path should be a big help in finding the offending part. Years ago I bought a Marantz 140 power amp that had been stored in the original box for years. It had an intermittent buzz in one channel that turned out to be a failing capacitor.

 

[MuseChaser]

Yes, this one does have adjustable gain via small pots on the back panel. I'll have to see if I can find the schematic online and start tracing. Thanks for the reply.