[Radio Wrangler]

I can't read component designators or values on the schematic.

The written procedure talks about opening power supply connections (one at a time) to each amplifier and measuring the current. Because other things take current, it has you measure with the amplifier quiescent current fully backed off, and then adjusting it to an increase of 3mA

This procedure was written in the days when most workshops did not have meters that would go down to millivolts DC, but could measure milliamps.

HOWEVER, this procedure is risky because one small slip while power connections are broken can destroy some semiconductors in that power amplifier, and tracking down which is a major undertaking. Several people on here have destroyed amplifiers doing this. It's especially nasty if it's one you just fixed.

A more modern way relies on sensitive DC voltmeters. Most decent hand-held DVMs will dothe job.

Between the collectors of the two high power transistors is a pair of resistors in series.... low value ones. With the amplifier on, but no signal, measure voltage between the two collectors. It'll be small. Take care probing. As a double check, away from the amplifier, touch both probes together and see what reading error the meter gives you with zero volts input. On the schematic, read the values of those two resistors and add them. Use Ohms law with the voltage you measured (correcting for the zero volts reading makes it more accurate) and you have the amplifier's quiescent bias vurrent in the output stage.

Take care probing.... one slip is all it takes and it's kaput. But this way you don't have to disconnect wires and restore them.

David