It appears a good spot to try is at the volume control where C201 and C202 are connected. Not at the center terminal on the pot but the top terminal, or the right side of R327 and R328, 1.5K resistors.

 

It appears a good spot to try is at the volume control where C201 and C202 are connected. Not at the center terminal on the pot but the top terminal, or the right side of R327 and R328, 1.5K resistors.

I connected it at volume control and it worked, but equalizer and speaker balance didn't work, then at R327 and R328 resistors balance started working but still nothing from equalizer.

Now I connected it to the right side of R323 and R234 resistors. Equalizer and balance are working, but for some reason VU meter doesn't work (I am pretty sure it worked before when I connected aux at volume control). I know it's not the most important thing, but since it's there it would be nice if I could make it work somehow. Any ideas where else I could try connecting aux?

In all of these cases the volume on phone had to be at 80% tops to avoid distortion like before, but now that's as loud as it should be. Its probably the speakers that can't handle more. Any suggestion for resistors I could use? Maybe I could just take pot from some cable of old headphones and set it to about 80%?

I also removed whole tape circuit pcb when I was soldering aux to these resistors, so I hope I wont need to connect anything there anymore.

 

Any ideas where else I could try connecting aux?

Try the right side of R343 and R344. They appear to be connected directly to preamp circuits that feed the tone controls.

Equalizer and balance are working, but for some reason VU meter doesn't work

Possible the output from the phone is loading down the circuit at that junction inhibiting the signal going to the VU circuit.

 

I suspect that the VU meter is only used during recording to the Tape Deck.

I have marked out the signal traces in RED and BLUE for you to locate and inject your AUX dual channel inputs.
Note that there is a MUTE switch down at the bottom of the circuit. This will have an effect on whether or not you receive any signal.

 

I added a clipping detector LED to the amplifier I designed and built for my TV so I can see that the clipping is from the TV station and not from my amplifier.
One time a TV station played stereo that had the channels out-of-phase. It sounded weird and switching the amplifier for L+R mono the bass was cancelled.

You need to see what is clipping. It might be your phone that is clipping when its volume is higher than 80%.
My new hearing aids have a stepped volume control that can go high enough to make it hurt. The compressor circuit is not working but the clarity and noise reduction is superb.

 

Try the right side of R343 and R344. They appear to be connected directly to preamp circuits that feed the tone controls.

That works, but now I have to keep phone volume under 50% to avoid distortion.

I suspect that the VU meter is only used during recording to the Tape Deck.

VU meter used to work on all modes... actually at the moment that aux is connected to R343 and R344 the only mode that it doesn't work on is tape.

I have marked out the signal traces in RED and BLUE for you to locate and inject your AUX dual channel inputs.

I tried connecting it at R313 and R314 (atleast I think that's what it says here). I got similar result as if I connected it to phono input.

You need to see what is clipping. It might be your phone that is clipping when its volume is higher than 80%.

If I understand right that would mean that my phone would clip while playing to other devices aswell?
Now on the VU meter everything above 50% on the phone shows in red color and below in green, while the radio volume doesn't matter.

 

Now on the VU meter everything above 50% on the phone shows in red color and below in green, while the radio volume doesn't matter.

Does that mean it's working to your satisfaction?

 

Does that mean it's working to your satisfaction?

Yes it is good enough. I will probably add another pot to replace current "record level" knob and call it "gain control". It will probably make the most sense since the best result is at about 50%, so right in the middle and if some song will be more quiet I could make it a bit louder there.

Sorry for dragging this for so long. Thank you all for your help. It was a nice welcome to the forum, I will definitely stick around