Polytone mini teeny brute problem

[prulup]

Okay doke. Pull the power transistors and report the voltages on the bases of the two driver transistors.

MJE 182 (NPN)
E 0
B 0,6
C 29

MJE 172 (PNP)
E 0
B -0,6
C -29

I know the MJEs have a different pinout than PU57s.
The bias potentiometer works, I can set the +- 0,5-0,6V on the MJEs.
On the pin 7 of the LM391 is cca 1,2V.

Also I found out there is a mistake in the schematics, the trimpot is not wired as a variable resistor (pin 1 and 2 ARE NOT conected). But it works...

[nickb]

OK that's a good enough range. Check R18 and R19 are not open and replace if necessary. Now set the bias pot to the position where you get +/- 0.5V on the bases of the drivers and check the voltage across R18 & R19 is <0.5V. If OK then you can replace the power transistors with known good ones.

Use the lowest power lamp you can find in your limiter until we are sure all is OK, 15W should be OK - the power rails will be low but that should be OK so long as they are not too low. Also set up to monitor the voltage across R20 or R21 before switch on (no speaker!!) for no more than 10mV. If higher quickly switch off and we'll need to figure out why. If OK take a look at the power rails and see if we have enough volts to make it work.