Altec 1270B Power Amp sizzle & crackle noise

[futuretimes]

I am am looking for support on an Altec 1270B Stereo Power amp.
One channel has an intermittant sizzle sound with an occassianol crackle and pop coming from the left speaker. It's not loud but never goes away. It still plays clear with equal power through both channels. I have repired audio and televisions but my expertise is more industrial than audio so I could use some direction. I had thought about swapping the 12000UF power capacitors.

Any tips?

Thank you,

Tim

[Don Moose]

I would expect if those big caps were going, you'd get more power hum than snap, crackle, pop. Besides, those monsters are common to both sides, and only one channel is giving you grief.

There's a schematic and manual here.

It might be worth cleaning the pots (POT cleaner, not contact cleaner) and checking the coupling caps before and after for leakage - pots in tube amps don't like DC across them, but that may not apply to the relatively lower voltage solid-state circuits.

Then, check the tightness of any jacks that rely on mechanical contact for signal ground.

Are any of the output devices getting hot(ter than others)?

Hope this helps!

[Enzo]

First thing i would suspect is the LF356 at the input of the channel. After that I'd look at the other low current semicondictors.