I am looking at the diagram here.
Since all the components needed to drive the output are OK, we can test with power.
The Out put transistors are not mounted during the test.

I am only talking about the Bad channel here so all the test points are on ch A. Fuse for ChA should be replaced. No power yet

Be careful...I am not there to see what you are doing.
1. Put the DVM in Resistance mode and see whether if the Negative terminal of the speaker shows 0Ω to the heatsink.. Since all the transistors collectors are grounded (virtual) (symbol P) the sink should have a direct connection to speaker negative terminal. If not check the channel B. If channel B confirm check why the Ch A sink is not grounded. Do not by pass or place any jumpers. Move on if OK if not (do not proceed ) check and post back.

2. Remove Ch B fuse first and then apply power. Wait for a few min to see if any thing smokes or smell around for burning smell. If fumes or smell cut power and post back. If nothing of the sort move on.

3. Place you finger on Q1 and Q2 ( heat sink, the little ones ) one by one. DO NOT PLACE ON BOTH SINK AT ONCE, I dunno if the sink is insulated or not. The sink voltage difference will be 126VDC, enuf to make say things you don't want to around any one and possible burn the fingers. If later you know the thing burning is your skin.
So place your finger on Q1 first and observe the heat. It should be cool to the touch. Then Q2, same as before, cool to touch. Both temp should be same. If reasonably different, there is trouble.
Remember to keep the other hand away from the amp chassis. Use one finger and one finger alone for this. Do not let the finger touch any thing else.

Do this and post back. If you hurry up, I might be here.

 

00:30 Hrs...Gotta go..Good Night.

 

So far so good. Heat sink is continuous with a & b speaker negative terminals.

No smoke.

Checked temperature of Q1 and Q2. Both felt cool (one at a time per your instruction).

I'll be going to sleep myself soon. Don't forget tonight is daylight savings. I'm guessing you don't really care about such crazy notions, am I right?

Talk to you soon.

 

So far so good. Heat sink is continuous with a & b speaker negative terminals.
No smoke.

Good.

Checked temperature of Q1 and Q2. Both felt cool (one at a time per your instruction).

That's a good indication so far

Don't forget tonight is daylight savings. I'm guessing you don't really care about such crazy notions, am I right?

I have no idea what you are talking about

I forgot about two important components to ask you to test before.

So first cut power, discharge caps and the meter in Resistance range measure the resistance of R17 & R18 of faulty channel. No need to remove them. You should get a reading of 22Ω as per diagram. Since the Power Tr. are removed you should not get any reading lower. If lower we need to check something else if higher than you need to replace them.
And do the Sink heat test on my previous post. The Resistors and the Output stage loads Q1 & Q2.

If them resistors are OK, we can move on. Do not continue the below method if the resistors are bad and if heat test fails. Below method is if R17 R18 are OK and heat test passed.
===================================================================
You will be measuring the voltage drop across R17 & R18 one by one. The reading will be around 0.4V to 0.6V.
Apply power and measure the voltage across R 17 and them across R18. Remember that measurement should be across, NOT referenced to ground or any where else. Across the Resistor. Careful while probing. Cause one slip and KAPOOOOW ! You might blow more components this way. Steady hands is a must. As power will be applied and I dunno what you will short if you slip the probe. So be careful..
Polarity is not important.
I need to know the readings to move on. And remember to monitor the Reading of each R for a minute or so as it will vary with temp. I need to know the variation if there is.
Then after that put the Negative probe on Speaker Negative terminal. Bind it to the post. DVM in Voltage Range, reading will be around 60V to 65V DC
Then put the Positive terminal on Base Q3 or collector of Q1( same track ). Note down the value.
Then put the Positive terminal on Base Q7 or collector of Q2( same track ). Note down the value.
Post your results.

We are almost there.

 

R17 and r18 are 22.1 ohms. With no power.

They passed the heat check.

When measuring voltage drop on a resistor under load, should dvm be set to diode mode?

 

Not Diode mode...DC Voltage.
I believe I said Voltage Measurements as you will be powering up the Amp.

 

Stand by.

 

Started out at .45 and got up to .620 as it warmed up. Still slowly climbing.

 

Both resistors or just one.

Is R38 Mounted on to the sink or just floating in Mid air. It needs to be mounted on the sink

When the voltage rises, check the respective transistor temp if you can for heat.
R17 goes with Q1

 

They seem to mirror each other.

 

Having trouble finding r38.

 

It will be standing up with a tab that can be screwed to the sink

 

R38a does not mount to sink. R38b does not either. Tried to attach a photo but can't do from iphone.

 

Does the voltage climb or stop at any point.?

Still you did not post all the measurements I need to know. Pls go thru the post and post results.

 

SOrry, didn't get that far. Still struggling with the first part.

I'll have to get the board back out of the case in order to check the collectors/bases. I'll have to do something to protect it since it will powered up but not fastened to anything and upside down.

I'll get back to you in a couple of hours. Sunday morning church.

Thank you for hanging in there on this one.

 

collector of Q1 is 66.2

collector of Q2 is 66.1

 

At this point I think your driver stage is ok.

I would install one good pair (one PNP and one NPN) output transistors and do the above tests with no load and no source.

Test the DC voltage at the speaker output with no speaker connected. Insert a 10Ω load in place of the speaker and measure the voltage across the resistor.

Do the finger test for temperature as before.

 

Hang on there Chips.
I have a problem with his readings.
I said to bind the Negative terminal of DVM to the Speaker negative.
So he should be getting a Negative Voltage reading. If it is typo he needs to confirm.
If he did what I said then the readings are wrong. I need to know which collector is giving a negative reading.

So do the below.
I need 4 measurements.
With the DVM negative connected to the speaker negative measure the Voltages at both ends of R17 & R18. Not across. Just measure them with positive probe and note them down. You should get two negative readings. I want to confirm this.

 

I thought you were supposed to be in bed.
Oh, I forgot, you don't need sleep.

 

Hey . .no double posting.
It's almost 00.00 hrs. I had to finish an emergency site job. So I guess I will be around for an hour or so.