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Pioneer Sa-706 - Phono Continuous Crackling

Hi there,

I could not find any post adressing this issue...

When set on phono, the amp produces a big crackling noise.
I don't even need to plug the turn-table to the amp for the crackling to happen.

The crackling won't fade and grows as I turn the volume up, making it impossible to use the amp.
The problem occurs whether I'm using headphones or speakers.

Not sure what to do to find out what the problem is or if a component is damaged or needs to be cleaned/replaced.

Thanks for your help.
Alex



Re: Pioneer Sa-706 - Phono Continuous Crackling

you might be able to troubleshoot this as follows :
connect a pair of modified phono cables to the phono input
(modified: strip 1 end of the phono cables and twist the center and shield wires together)
this will eliminate picking up external noise as you have now "shorted" the input.

if the switch is dirty as the other commenter, rightfully, suggested, jostle the switch after cleaning to see if it causes your problem.

if after cleaning the switch and inserting the shorted phono cables, you still have the problem,
then you may have some noisy transistors. IF you're getting scratchy noise which
increases and decreases by itself from ONLY the phono section there's a good chance
it could be noise from transistors. Rather than desoldering and cleaning the leads and re-installing I would look at just replacing the transistors. noise would be generated internally in the transistors.

one of my very first "professional" repair jobs in the late 70's was trying to repair a
noisy phono section. that's when I first learned about "noisy" transistors. The hard way.

Re: Pioneer Sa-706 - Phono Continuous Crackling

The phono interference filter switch on the back may be dirty. There may be corrosion on some or all of the transistor leads; if these leads are discolored or black they will need to be resoldered at the very least. Sometimes it's necessary to remove them for cleaning before resoldering. Transistors can also fail internally.