On Saturday, October 31, 2020 at 9:51:07 AM UTC-4, T i m wrote:
Hi all,

Chatting to a mate the other day and in passing mentioned his old
Technics SU-610 amp, seems to have lost one channel and might I be
able to fix it (I've just fixed a car battery charger for him). ;-)

He said if he turns the balance fully to that channel and the volume
fully up, he can just hear something from that speaker.

I've suggested he try some tests ... actioning all the switches,
swapping the input leads over L/R, trying a different input, checking
the speaker connections / swapping the speakers, trying the headphone
socket etc and to let me know the outcome.

If it proves to be faulty and it comes to me, I've picked up one of
those PC USB scopes (It was bought by my mate for his PC shop but
mainly used by me there ... and he's not used it since he retired) and
so I just need a signal source (any simple sine wave generator kits
out there?), the schematic (got) and I'm good to go.

The schematic looks pretty simple (even for me g) but I'm guessing
it's likely to be the main hybrid amp module, an SVI3102B and I see
they are still available for not a lot of money (new / used).

Along with the basic tone generator question, does anyone know this
model and is aware of any 'typical' fault causes / weaknesses / mods
please?

Cheers, T i m

I can't tell you how many of those came in over the years with cranky switches, either the rotating or sliding kind. Yes, by all means have him manipulate them or test those first if it shows up. If it responds, clean them accordingly.

The good news is that a stereo amp with one weird channel out of two identical channels is one of the easier things to troubleshoot in the consumer electronics world.