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RE: Maintenance Issues with Older Amps

With an older amp, of most concern would be the electrolytic caps, particularly the main supply caps, which usually dry out with age. This may occur at a slower rate in better quality/cooler running/more conservatively designed amps. There are usually warning signs of cap failure such as hum, bulging of the can, and leaking of electrolyte. You may get differences of opinion about how long caps should last in an older amp; IMO it should be at least 25 years before one would need to consider recapping an amp.

I've recapped some older amps and I've also left some others alone. Right now I have a 33-year-old Phase Linear 400 Series 2 to which I have added DC protection circuitry and upgraded the input and output connectors, but left the original caps in place for now. I've decided to adopt an "if its not broke don't fix it" approach.

Bias and DC offset in an older amp may also need to be checked and adjusted if necessary. This is usually not difficult to do with most amps; there are usually trimpots for making both adjustments. If you are handy with a digital multimeter, working with electronic equipment, and have the service manual or service procedure for making the adjustments, its a DIY project. In a handful of amps there is no adjustment method for offset and if the offset figure is out of spec, the input differential transistors will need to be replaced. BTW, I have a Classé CA-300 purchased in 1996 that is in fine operating condition.





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