Toshiba RTS 933 right channel apparently dead

as the title says, the right channel is dead or nearly dead
1) with the balance in the middle, only hear the left channel, and by increasing the volume begins to distort
2)when move to the right channel, the volume begins to decrease until they hear anything in both channels.this happens on all inputs, radio / tape / line and phono-
3)connecting headphones is exactly the same.
4)clean all switches without getting any results.
5)I checked things. tape recorded and played in another box and heard in sterero smoothly.
connect it to another box using the output of line out and listen to 2 channel smoothly, with the same signal without distortion apparent.
when using the external speaker output, the left channel works , the right output signal does not have any signal.

for now is the little test I could do.my knowledge of electronics are close to zero!any idea or suggestion is welcome to try to check

some pictures of the interior

Honestly sounds like a roached AMP chip

Maybe a stupid suggestion...but did you clean the record/play switch on the tape board or wherever it is located?

Yes you should clean all pots and switches, especially the function and band control

If spraying the pots & sliders doesn't work, you could try:

Checking connections on your bad channel - could just be a loose joint on the speaker at either spk or board end.
Disconnect your 'bad' spk & connect your good one to the bad channel - just to prove its not the spk & the fault lies with that channel.
Check for visual damage to the speaker cone - rips creases etc...
Have a look on the Board for dry solder joints.
If your feeling really confident & with the unit switched on, get something non conductive & have a tap [gentle taps - no drum solos ] around the board especially the sound chip

Hope that helps.

Check through headphones before swapping speaker. It could also be a dirtyrusty headphone jack cutting the channel to speaker

thanks guys for the suggestions, this weekend will try some more. did not see the bar tape / play, the typical long.
looketh in more detail and I'll upload some photos.

i'm really curious to see how this turns out....do you think you could go ahead and get going on this

this is the part of the amplifier (I think lol), Black and Red arrows indicates external speaker outs ,Blue(L) and yellou (R) and the ellipses red and black ,are the chips.
that could be measured in this area?
more pictures, so you can see some more details