Sony STR-7045 Tuner Intermittent Static

[Johnny_Law]

I'm dealing with a funky tuner in my STR-7045 (all original inside). I had an STR-6055 previously (the exact same unit) which had wonderful FM reception (although I had recapped the tuner boards).

My STR-7045 pulls in stations great and sounds fantastic ... for a while. It will randomly burst into complete static, and stay in static for a minute or two, and then snap out of it and the static disappears. This happens in both mono and stereo, with and without FM muting selected. In Stereo mode it gets louder and more intense, in mono it is less intense but still present. I have cleaned the tuner according to @dr*audio guide, but all caps and etc are original.

I've found a variety of threads discussing Sony STR tuner issues but none seem to report these precise symptoms. Any ideas?

 

[bzb882]

The STR-7045 service manual shows quite a few 2SC631 and 2SC632 transistors. They're prone to noise and/or failure. That said, I rcapped mine in November and found none of them....

 

[Johnny_Law]

Hmm, thanks, a couple 2SC631 and 2SC633 in the MPX decoder. Perhaps measuring reference voltages during a period of static will shed some light on it ... in the meantime I need to check my stock of KSC1845.

 

[Johnny_Law]

Another interesting thing, the stereo light pulses with the music, especially with bass notes at higher volume.

I wonder if this implies that the power supply needs a refresh.

 

[Punker X]

Another interesting thing, the stereo light pulses with the music, especially with bass notes at higher volume

This is a typical symptom of the discriminator needing alignment.