Sunn Concert Bass (Blackface) Restore Help

[misterc57]

I bought this amp head knowing it had undescribed issues needing attention.

At idle I see around -34 VDC at the output jack with no load, and around -25 VDC with a 8 ohm dummy load

This amp has two 6800 uF filter caps and one bridge rectifier. I have attached the schematic which I think may be the correct one.

Still trying to learn solid state amplification workings.

I can see work had been done before on the amp board. See pics.

This schematic shows a + and - 34 VDC rails at the output jack. Does this mean there should be 0 VDC at the output jack? And it looks like the 5W 22R at the output was a replaced component along with some messy work on the underside. Don't care for all the glue on the top and bottom side.

I have plus and minus DC on the relative rails.

All four 0.33R 10 watt are showing negative VDC (in the -27 to -30 range).

Looks like one of the final 5 output transistors has been replaced. The other four are Toshiba Japan

The entire amp is showing a current draw of about 1.25A at the variac meter.

Need guidance. Thank you, Mark

[Jon Snell]

Q1 is a driver transistor, not an output transistor.
There should be 0volts between the speaker out and ground.
The 0volts is determined by the two resistors; R112 & R114 providing a centre voltage equating to 0volts.
There should be no more than 60mA draw when sitting with no signal and no load.

There are a few burnt resistors and bad repair work possibly from the previous repair. That will be a fun project.