Derek92994's 700 Ser II White Oak conversion

[Gepetto]

If you are not blowing fuses and haven't been blowing fuses, and not seeing fire and brimstone, then the amp is being commanded to do this by a fault likely on the control board.

Have the +/- 20V rails been checked yet?

 

[laatsch55]

No. Not yet Joe.

That was next. With + rail voltage on both channels that was my suspect.

 

[derek92994]

Im about to go to work, the info I require is the exact thread with the 14-20 steps I need to follow to debug the control board.

 

[derek92994]

Sorry I missed the post, I see it now. Will update you, thanks guys

 

[derek92994]

I wonder if it could be a wire strand or ball of solder under the backplane. Both meters have this behavior on shut down, yes? Most likely a power problem. Maybe pull the B+ fuses (the ones on the upper side), try it again. If it still happens pull the B- fuses (the two lower ones).

If it still happens I would remove the Output Transistors one column at a time and try it. If that has no effect, you will have to remove them all anyway to pull the Backplanes away from the chassis.

BTW, is your chassis bare aluminum? It looks silver in the video.

thank you for the info and ideas, much appreciated.

 

[derek92994]

Big work day and a long counselling session. Earlier finish tomorrow so will get more time to dive into control board debugging.

 

[derek92994]

Some Pics of low and high voltages

 

[derek92994]

Okay, we are getting 7.6 Volts where there should be 19.9. No wonder the WOPL is skitzo

 

[derek92994]

Meanwhile, the Pioneer is doing its best with the fans at full speed. WOPL is Laughing its ass off, it knows its coming back

 

[derek92994]

I know that if the voltage isn't right, then shit aint gonna go well. I shall await on your advice fellas. Cheers.

 

[laatsch55]

Now, we need to see what are on the output legs of the regulators. Tape off all but the tip of your probe and check the outside legs of the TL-431 (TO-92's) in the middle of the board. Be VERY careful...

 

[derek92994]

Left Hand Side TO-92:
Pin C: 0 Volts
Pin A: 20.5 Volts
Pin R: 17.9 Volts

Right Hand Side TO-92:
Pin C: 7.6 Volts (Peaks to 20.2 Volts shortly after power down)
Pin A: 0 Volts
Pin R: 2.5 Volts

These Parrot Clips are great:

 

[laatsch55]

Where you have them written down, were there any negative voltages?

 

[derek92994]

Where you have them written down, were there any negative voltages?

-20.5 and -17.9 from the pics so far

 

[derek92994]

Only one I'm unsure about +/- is the 7.6 one, as the pic does not reveal the negative symbol due to angle of the photo.

 

[laatsch55]

Hookay...headed to work Darc..

 

[derek92994]

Negative terminal on the bus bar.

 

[derek92994]

Roger that, take care bud

 

[laatsch55]

Sir Joe, if there was a short on the board, could it pull the voltage down all the way to the TO-220'S????

 

[laatsch55]

The low voltage...