Help with Pioneer phono input

[antmax]

Hello everyone. I have an old Pioneer amplifier SA 710. It has always worked very well, but for this morning the Riaa channel (left channel), emits almost exclusively static noise and Crackles. All other inputs (tuner, tape 1 and 2, aux) work very well. The static noise and the crackles increase or decrease in intensity depending on the volume, so I suppose it is the Riaa circuit of the preamplifier, and not the final stage. Can someone help me? Thank you

 

[WaynerN]

This could come from the selector switch for the phono input, not making good contact. MIght use a shot of Deoxit-5. For now, rotated (or push buttons) back and forth a bunch of times to try remove tarnish on internal contact(s) of switches, see if that helps.

 

[Blue Shadow]

could be a bad transistor needing replacement. Check circuit components against bad transistor list in the sticky in solid state, I think.

 

[MegaHurts]

Hello everyone. I have an old Pioneer amplifier SA 710. It has always worked very well, but for this morning the Riaa channel (left channel), emits almost exclusively static noise and Crackles. All other inputs (tuner, tape 1 and 2, aux) work very well. The static noise and the crackles increase or decrease in intensity depending on the volume, so I suppose it is the Riaa circuit of the preamplifier, and not the final stage. Can someone help me? Thank you

Can you check voltages on op amp? I'd expect the one or both channels to be completely dead instead of the noise though.

 

[antmax]

Thank you all, i've tried to use Deoxid on the internal linear switcher, with no luck. I think that Blue Shadow coud be correct, there are three 2S4978 transistors per channel on the phono stage, maybe one of these is damaged.

 

[E100]

Hi. I have a similar problem , there is no sound from LCH of phono. How did you solve the problem at your amplifier? Thanks.