So another bit of bench time spent on this receiver. New output transistors and drivers. Replaced the factory power supply caps. Brought up slowly on the variac and watched for amperage spikes…nothing. Seems to be powering up well and not blowing fuses anymore. On to bias and alignment.
To bias idle current of this amp you need to take reading on the emitter legs of the output transistors which makes sense. Then remove a solder bridge and test the DC offset. I guess a jumper would have been too much to ask for. After setting idle current went to set the DC offset. Here is where the fun began. Remove the solder bridge and power back up; within five seconds two resistors are glowing red. Awesome. Power down and recheck. Power up…glowing resistors. Hmm gonna have to evaluate this even more after replacing the now ruined resistors.
On a good note the power caps that were replaced appear to have solved the amperage spike that was destroying fuses. One problem solved. Now to just figure out why the bias issues. This little guy better sound good after all this trouble.