Mystery Circuit

[lowell]

Have a Proficient Audio S12 powered sub. No output. Have -16v on output protect relay. All 8pin opamp have no +V on pin 8. I cannot find any regulators or zener diodes to fix the low v rails. I called the company and they have no info on it. It's a very capitalistic product and a throwaway when broken ideology.

It has 1 2SA1943 and 2SC5200 BJT power transistor. So I'm guessing it's a pretty common off the shelf design. Also has TIP41/42 as well. Drivers?

I also found one 1/8w resistor that's toast. It connects to a TIP41C BASE and a smallish transistor - 2SA965 collector. The other end of the resistor is connected to the high -V rail. My guess is the 2SA965 is a Vbe multiplier (bias transistor/rubber diode)?

Any comments appreciated and if anyone has one of these laying around I need a value for R186 near the TIP41/42 which are mounted to the plate.

[lowell]

Maybe the resistor is a 2k2? This is somewhat similar.

[lowell]

Well I took a guess at that resistor and put a 2k2. Then replaced a shorted KSC1815 with a 2n3904... making sure the EBC were correct since the transistors aren't identical in lead layout. Then after tracing the low voltage rail circuit figured the B722 and B822 are BJT regulators. The working negative rail measured 1.2k from C to B but the missing positive rail had a 50k resistance reading there. Again took a guess and put a 1k2 in there. Fired it up...no smoke...and it WORKS. I'll be damned. The Base wasn't tied close enough with the collector so the regulation couldn't happen.