Hello,
I have tested : the amplifier seems to be OK

. A cool guy from Sri Lanka, Dilshan Jayakody, is also helping me, he's very patient

The 2 vu-meter only works with tape deck, not with radio, but I think it is normal.
There is a problem with light bulbs of the 2 vu-meter : I have removed the light bulbs because they were dead. there is + and - (look at photo) but there is electricity on + and - too.
I have study the service manual (I have tried). The 314 is the + of the lights bulbs and the 315 is -. The 314 and 315 plug to M414 and M415 on the amplifier board. But there is electricity coming from M415 and it is not normal.
Now, I wait for a new spring for the tape deck (a factory will make exactly the same for me but it is expensive for a peace of iron 30 usd

).
I would like to put a little spring. If someone has a photo.
For Superlew : it is ok for you ?