Recent content by TimD

True, but then again, a switch/breaker combo instead of fuses does have it's merits (as typically found on pro level amps).

Myself, I'd grab a voltmeter and start at the relay and work back towards the switch. Despite the obscurity on the schematic, that circuit does not appear to be terribly complex, and I would think that the fault would reveal itself rather quickly. You also mentioned blurry schematics . . . the...

Hmmmm . . . You put the larger caps in with the WOPL stuff, right? You might check the main bridge rectifier to see if it has failed due to the higher inrush, or (god forbid) one of the caps was installed backwards and has failed into a short. A bit of a longshot, but not impossible...

Sounds like latchup, but with your components, that's not supposed to be possible . . . .

I don't have it handy at the moment, but the procedure is in the service manual.

Thanks. I don't have silpads, but have plenty of grease and mica, so sticking with that . . . Hard to see a reason to change what's not broken, and as noted, the PL docs indicate a possibly increased tendency to oscillate on silpads, and recommend mica . . . Not sure how real that is, but can't...

Thanks . . . Thought I had covered that under "Changing out the transistors" (this unit, while working, has the SD555 (or close?) parts, and I do plan to swap to the current complimentary pairs and matching drivers). I had just not focused on that here since I was more focused on circuit rework...

There is a service bulletin covering the changes to comp, but the change happened late enough that that is all that I think exists.

Competent technique does not lift traces . . . and only 4 caps to change. I work on stuff this ood (and older) routinely with zero issues (and no traces on the backend to damage in the first place), so while I appreciate your response, it's a direction I have zero interest in at this point...

Just wondering if anyone has done this prior *WITHOUT* changing out boards or backplane. It looks pretty trivial - the PL service bulletin seems to indicate that the only change to the PL36 is adding R127 and R128 (56K), and it looks like the backplane change is simply flipping the emitter...

If there are no diodes, and no short, the resistance will be very high, indicating that that channel is good. Thus, on those tests, the channel with the *low* resistance has the fault.

I'm still trying to figure out what test points he is reading across . . . reread as many times as I can, and I still never see it mentioned, so cannot possibly make an observation. As noted, good semiconductors should show conductivity in one direction and not the other across the junctions...

Absooutely anything that can provide an inverted signal to one channel and a non-inverted signal to the other can bridge an amp with a common ground for the two outputs (the only things that won't bridge are amps with differential outputs, and a few other oddities). There is absolutely nothing...

Build *just* U5B from the schematic - that's the actual line level inverter. The rest is a crossover, none of what you need to bridge an amp (and you only need a *single* amp to bridge). If you are trying to do a sub setup, that looks like it would work as a crossover. If you have two subs, and...

You can do it with an active inverter as well - no need for a transformer. Most amps that support bridging internally use a simple op-amp inverter to feed the second channel from the first when set to bridge.