Where to find 6000uF 50V replacement cap cans??

[g1]

Still can't get any mV reading across the 0R68 power resistors?
Those are the only 2 that will show idle current.  Q15 and Q16 will be off when idling.
The '97 model uses the same basic power amp but they have removed the 22R resistor that is across D8.
I would try removing that one and see if you can then get a reading across R55,R56.  Start with the trimmer full CCW.
If you can, and the pot is now too sensitive, change the resistor across the pot back to 47R (instead of the 100R you put there).

[RG100ESROX]

Still can't get any mV reading across the 0R68 power resistors?
Those are the only 2 that will show idle current.  Q15 and Q16 will be off when idling.
The '97 model uses the same basic power amp but they have removed the 22R resistor that is across D8.
I would try removing that one and see if you can then get a reading across R55,R56.  Start with the trimmer full CCW.
If you can, and the pot is now too sensitive, change the resistor across the pot back to 47R (instead of the 100R you put there).

Okay... I pulled the 22R from the board, and with the trim pot FCCW, I get 0.0V across both .62 resistors. Now, if I turn the trim pot CW to the 8:30 position, the voltage rose to .05VDC.

I would have increased the trim pot further, but I wasn't sure if I should.

But, we have voltage there now.👍🏻👌🏻

Q: What lead you to the 22R...? And why did the amp work with it before I broke it??

[g1]

We are now adjusting bias, not making the amp work.
It will work without the output transistors running idle current, and may well have been doing so before you ever touched it.
You found originally that it could only be turned up to 25mV across the 0R68, but it may have been set at zero.
Changes to the drivers and output transistors may have resulted in no longer being able to get any reading at all, due to variance of the new parts.
The reason I looked to the 22R was that you were not getting sufficient voltage difference between the driver bases (Q11 and Q12).
With 2 diodes in the bias string, normally there would be around 0.7V drop across each.  But with the low resistance of 22R across D8, the voltage across D8 would be reduced.
Looking at the '97 schematic confirmed my suspicion, as they have removed it for use with the more modern output transistors. (see attached)
Your scope shot in post #143 shows no evidence of crossover distortion, and that was before you had any mV reading across the 0R68's.  Crossover distortion would show as a notch in the sides of the sinewave.
It will usually be most evident at low volume levels, so try doing that same test on the scope, but with very low output, like 50mV peak to peak or something like that.
I don't think it will matter whether a load is attached, but you are probably ok to try that now too.

[RG100ESROX]

We are now adjusting bias, not making the amp work.
It will work without the output transistors running idle current, and may well have been doing so before you ever touched it.
You found originally that it could only be turned up to 25mV across the 0R68, but it may have been set at zero.
Changes to the drivers and output transistors may have resulted in no longer being able to get any reading at all, due to variance of the new parts.
The reason I looked to the 22R was that you were not getting sufficient voltage difference between the driver bases (Q11 and Q12).
With 2 diodes in the bias string, normally there would be around 0.7V drop across each.  But with the low resistance of 22R across D8, the voltage across D8 would be reduced.
Looking at the '97 schematic confirmed my suspicion, as they have removed it for use with the more modern output transistors. (see attached)
Your scope shot in post #143 shows no evidence of crossover distortion, and that was before you had any mV reading across the 0R68's.  Crossover distortion would show as a notch in the sides of the sinewave.
It will usually be most evident at low volume levels, so try doing that same test on the scope, but with very low output, like 50mV peak to peak or something like that.
I don't think it will matter whether a load is attached, but you are probably ok to try that now too.

Great!! Thanks for the explanation. I appreciate you taking the time.

Thanks for the attachment as well.

I'll get back to you with some screen shots of the sine wave.

What CAN I adjust the trim pot up to safely?? Because we know FCCW we got no voltage across the .62R's.

[RG100ESROX]

Looks like our perfect sine wave is no more...(I'm hoping this is what you expected?)

First photo is with the trim pot FCCW.

Second is with it set to the 8:30 position.

The sine wave didn't change much with the gain or volume, but it did with the treble...and the increase in the bias pot.

Q: where should my settings all be when taking a sine wave?

[g1]

There is no signal there.  Just noise and ripple from the power supply.  Are you still injecting 3Khz?  What level of 3K were you injecting before, and what now?

[RG100ESROX]

There is no signal there.  Just noise and ripple from the power supply.  Are you still injecting 3Khz?  What level of 3K were you injecting before, and what now?

Sorry for wasting your time. I don't know what was going on there. It just worked for some reason last time I hooked everything up.

Yes. Injecting 3kH @ .5v....

Does this look better?

[g1]

Is that at the output of the amp?  It looks good, but would like to see at a much lower level.
Drop your source voltage from .5V to .05V if you can.
That should drop the output voltage to about 1/10th of what it is now (4Vpp).

[RG100ESROX]

Is that at the output of the amp?  It looks good, but would like to see at a much lower level.
Drop your source voltage from .5V to .05V if you can.
That should drop the output voltage to about 1/10th of what it is now (4Vpp).

I'd like to oblige, but my cheap-o signal generator won't go any lower than .1V.

I'll give that a try and send ya some pics. I hope that's low enough.

Back in a few...

Here ya go. Not sure if this gives you what you wanted.... I set the SG to .1v, but it only went down to around 1.5Vpp at its lowest.

Added note: The .62 and/or .27 (not sure which) are getting hot. I can feel it when I hover my hand over them.

[g1]

Do you have a load connected?  Otherwise the outputs shouldn't be getting hot.

[RG100ESROX]

Do you have a load connected?  Otherwise the outputs shouldn't be getting hot.

No. I have a 50W 8R and 16R dummy load. I'll plug it in.

[g1]

No, if you are getting heat you should not connect load or speaker.
Not sure why you are getting heat on the power resistors with no load.
Possibly your meter is not registering the real DC voltage across the 0R68's ?
How good is your meter, especially at low mV levels?

[RG100ESROX]

No, if you are getting heat you should not connect load or speaker.
Not sure why you are getting heat on the power resistors with no load.
Possibly your meter is not registering the real DC voltage across the 0R68's ?
How good is your meter, especially at low mV levels?

Okay. No load. (-;

If I check the voltage at the positive side of the power resistors. I get about 42.0VDC on the far right resistor. On the left pair. I get about .16mV...if I remember correctly.

[g1]

Well, previously you said there was 0V DC at the speaker output.  How can there be 42V at and emitter resistor?  Is it open, or do you have DC on the output now.

[RG100ESROX]

Well, previously you said there was 0V DC at the speaker output.  How can there be 42V at and emitter resistor?  Is it open, or do you have DC on the output now.

There was no voltage drop 'across' the resistors. With reference to chassis ground on the positive side of the two far right power resistors, I get about 42.0VDC. Across the resistors there was 0.0V.

I'll check for DC on the output, and check the voltage of the two resistors again...

-42.0VDC on the far right .62R and .27R +, and  -.020mV on the far left power resistors +.

On the output I have  -.022VDC.