Sansui AU717 protection issue

[moosefriend]

first time poster: I’ve got a AU717 on the bench with a problem I haven’t been able to nail down. It turns on, protector light flashes, protection relay clicks, left channel comes on but no right, after 5-10 minutes right channel snaps on and everything works normally. I have set the bias voltages and confirmed all are in spec with the service manual, I cleaned pots, cleaned the switch on back and worked it several times. No change after all that. I’ve tried tapping the relay as a last resort, it didn’t trigger the right side on.

I’m thinking I’ll be tracking something down in the power supply, any suggestions?

 

[slimecity]

Try the speaker B outputs and see if the same thing happens there.

 

[petehall347]

you could use rca cables to cross over left and right pre to main and see if it swaps sides .

 

[moosefriend]

I didn’t mention that, yes the problem is on both A and B outputs

 

[moosefriend]

you could use rca cables to cross over left and right pre to main and see if it swaps sides .

Switches sides=issue on preamp?

 

[petehall347]

looks that way .
maybe tape switch .

 

[skippy124]

Hi and welcome to AK and the Sansui forum

It could be the preamp power supplies. You can measure the pre amp power supplies for each channel at the top corners of the power supply board (red and blue wires to chassis, and yellow and grey wires to chassis). Should read around + and - 33V dc.

Cheers

John

 

[Robisme]

Hi and welcome to AK and the Sansui forum

It could be the preamp power supplies. You can measure the pre amp power supplies for each channel at the top corners of the power supply board (red and blue wires to chassis, and yellow and grey wires to chassis). Should read around + and - 33V dc.

Cheers

John

This.

I had one that did the same thing, but took 30 minutes for the second channel to kick in. Voltage to one channel was slow to come up. Needed a power supply rebuild.

Rob.