BIG problems

[Michael F]

And that is with all 4 fuses removed, correct?

Yes. Out of circuit measure good, check my most recent post

 

[laatsch55]

Measure accross the resistor on the driver transistors on the bottom row. Less than 150 ohms is not a good thing.

 

[jbeckva]

Yes. Out of circuit measure good, check my most recent post

Saw it. So assuming the fuses are still out of circuit, yeah.. you had something pretty destructive happen, eh? Issue now is that with the emitter resistors themselves only being either .27 or .3, it will be hard to find the right output or however so many* that is bad. You can isolate by pulling the emitter resistor off and remeasuring, one by one.

* = I recall with working on a previous one that over 70 percent were toasted.

 

[Skratch]

HOUSTON!!!!! I think we have a problem????? I agree with Lee, If any of the banks have less than 150 ohms its time to start yanking outputs and drivers?

 

[Michael F]

OK, the transistors on bank 1 that measure 11R are fine then. I`ll now remove all remaining outputs and drivers for out of circuit measurements.
Will the same Collector to Emitter test be sufficient or should I do B to C and B to E as well?

While they are out, would that be a good time to test the emitter resistors?

 

[laatsch55]

No. Standard NPN diode test.

 

[laatsch55]

+ on base, - on emitter then collector. Reverse leads and do it agsain.

 

[laatsch55]

Excellent time to check ER's.

 

[Michael F]

A big thanks to all who chimed in so far. I`ll post after my individual transistor test, looks to be labor intensive.
Do I reinstall the ones that are good? Can grease and mica be reused?

 

[laatsch55]

No, we'll have you power back up the Gepetto way. Just the drivers first then one row of outputs, then another, then another...

 

[laatsch55]

I'm really interested in knowing if any drivers are shorted. If any are there are some components on the board that are toast too. Got new micas and fresh grease??

 

[Skratch]

I would put a couple of outputs back in each bank after testing to hold the TO-3 sockets in place so you dont have a problem aligning them up later.

 

[Michael F]

I'm really interested in knowing if any drivers are shorted. If any are there are some components on the board that are toast too. Got new micas and fresh grease??

I`ll check those Sunday. Are you saying that if outputs are blown, there would be no upstream damage but blown drivers are an indication of upstream (driver board) nasties?
As you can probably tell, I don't do much component level troubleshooting or repair.
The idea of that kind or work frightens me. Would it just be more logical and place an order with Joe should the need arise?

 

[Gepetto]

No, we'll have you power back up the Gepetto way. Just the drivers first then one row of outputs, then another, then another...

Check Q7 and Q10 on the control board as well before powering up with only the pre-drivers in. If they are toast, it will take out the 10 ohm bias resistors.

 

[laatsch55]

I`ll check those Sunday. Are you saying that if outputs are blown, there would be no upstream damage but blown drivers are an indication of upstream (driver board) nasties?
As you can probably tell, I don't do much component level troubleshooting or repair.
The idea of that kind or work frightens me. Would it just be more logical and place an order with Joe should the need arise?

In for a penny, in for a pound. Just as well White oak it. If you can afford to do so at all , nows the time.

 

[laatsch55]

D8, D9 are always suspect after a shorting event, Q5 too.

 

[Michael F]

In for a penny, in for a pound. Just as well White oak it. If you can afford to do so at all , nows the time.

I was considering that upgrade but not like this. I would sooner install a populated and tested board rather than dicking around with something beyond my comfort zone.

It`s not looking too good with the output transistors either. Correct me if I`m wrong, but I was always of the impression that one does not replace ONLY the bad units , but all.
If I`m right, I`m looking at quite the worse case scenario. There are several options to consider.
There is no guarantee the amp wont go Supernova again, look what happened with a simple relay install I cant go through that again..
On the other hand, I`m sitting on a pretty boat anchor in it`s present form...

 

[laatsch55]

How many outputs are bad?? You can replace any that are bad with the same type in the same channel. XPL-909's, XPL-910's, FPL-909's, MJ15024's etc..

 

[laatsch55]

The relay did not cause the destruction you are seeing there. It looks like a mechanical short followed by an electrical short. I've installed a lot of Don's relays. The only problem I've had is when he re-spec'd the Zoebel resistor with a very inductive type, leads to oscillation.

 

[Phase Linear Phanatic]

In for a penny, in for a pound. Just as well White oak it. If you can afford to do so at all , nows the time.

Awesome!!