audio (vinyl player) amplifier problem

[gimme23]

Please forgive my poor English . I have an old 1989 year soviet union vinyl player. It has nice sounding speakers and a good amplifier.
I have used it as amplifier for four years. About two weeks ago, when I had shortly listened some music, it suddenly stopped amplifying.

You can still hear very low music and some static or something. The static goes louder when I turn the volume up.
Besides there is no difference whether the signal comes in from line in or from microphone input.
I break up the thing and controlled most of the wires and circuits with my multimeter and my small amount of knowledge. Everything seem to be okay.

Could someone advise me what is the problem. I attached a picture but when needed i have more accurate and specific pictures too.

 

[(*steve*)]

Is it mono or stereo? If stereo, does it affect both channels?

How high was the volume when the fault developed?

Are there any other symptoms (say indicator lights that don't come on, etc.)?

Does the sound you can hear seem to contain more high frequencies than low frequencies?

Have you checked the speakers?

 

[gimme23]

Is it mono or stereo? If stereo, does it affect both channels?

It is stereo, and yes it affects both channels. By the way there is a button that combines the two channels. After pressing it the problem persists.

How high was the volume when the fault developed?

When the fault developed the volume was a bit below mid-range.

Are there any other symptoms (say indicator lights that don't come on, etc.)?

I discovered now that when i put the input to input and turn the input on there is no very silent music. Same with the mic in. But when the input is in input and i turn the mic in on. There is very silent music. I haven't found any other symptoms.

Does the sound you can hear seem to contain more high frequencies than low frequencies?

I could not tell, it is the basically the same sound as it been always.

Have you checked the speakers?

No i haven't.

 

[(*steve*)]

I discovered now that when i put the input to input and turn the input on there is no very silent music. Same with the mic in. But when the input is in input and i turn the mic in on. There is very silent music. I haven't found any other symptoms.

OK, I can't understand this bit.

However, since both channels are affected, the problem mat be due to something that is common to both channels.

The power supply is a good place to start.

Measure the voltage on the power supply and compare it to the nominal value (which hopefully is printed somewhere).