WOPL 400 Build Problem!

[laatsch55]

And it didn't blow a fuse?

 

[nadude98]

And it didn't blow a fuse?

Nope, it didn't. I must have discharged enough of the power from the caps to be under the threshold... i guess?


Methinks I need to bake a new batch of brownies.... totally stressing!

 

[nadude98]

Any ideas or thoughts...?

 

[nadude98]

Yes sir!

Actually, it sounds great until I go above a certain volume.

 

[laatsch55]

Any guesses on what power level?

 

[nadude98]

Any guesses on what power level?

nope... but I just did a test of voltages on the PL 14-20 board, not good. This is the test with only pads 3, 5, 7, 11, 12 connected.. also bias connected. By pad and each channel L then R
1 0v 0v
2 0v 0v
3 -83v -84v
4 -190mv -24v
5 0v 0v
PNP -17v -24v
6 0v 0v
7 84v 84v
8 50mv -23v
9 4mv -80mv
10 -130mv -320mv
11 84v -23v
12 -84v -84v

test points +15v 1.4v
-15 -15v

 

[nadude98]

I think I'm in over my head here....!

 

[laatsch55]

Desolder pad 6 and 9 from each channel on the board. Tape the ends, power up on the DBT, measure voltages again, on the board, not the ends of the wires. you are removing the base drives and this will isolate the problem to either the board or the backplanes.

 

[laatsch55]

6 and 9 are the only ones we want separated from the board. Gotta get up way early tomorrow, later bud....

 

[nadude98]

6 and 9 are the only ones we want separated from the board. Gotta get up way early tomorrow, later bud....

okay, thanks for the help.. I'm sorry for being pain.

 

[nadude98]

6 and 9 are the only ones we want separated from the board. Gotta get up way early tomorrow, later bud....

Pad 1 0v 0v
pad 2 0v 0v
pad 3 -81.2v -81.2v
pad 4 -21v -24v
pad 5 -.5mv .2mv
pnp -22v -25v
pad 6 -1.2mv -150mv
pad 7 82.6v 82.6v
pad 8 -21.5v -24.5v
pad 9 -21mv -135mv
pad 10 -21v -24.5v
pad 11 82.5v 24.5v
pad 12 81.4v 81.4v

test points +15 15.6v
-15 -1.4v

 

[laatsch55]

Do a transistor test of the TL 431 TO-92 voltage regulator. It tests like an NPN. You are way short of negative low voltage...

 

[laatsch55]

okay, thanks for the help.. I'm sorry for being pain.

You are not being a pain, been there myself bud, still go there occasionally....

 

[laatsch55]

Pad 1 0v 0v
pad 2 0v 0v
pad 3 -81.2v -81.2v
pad 4 -21v -24v
pad 5 -.5mv .2mv
pnp -22v -25v
pad 6 -1.2mv -150mv
pad 7 82.6v 82.6v
pad 8 -21.5v -24.5v
pad 9 -21mv -135mv
pad 10 -21v -24.5v
pad 11 82.5v 24.5v
pad 12 81.4v 81.4v

test points +15 15.6v
-15 -1.4v

Pad 12 should be negative rail voltage, is it really showing positive? Pad 11 on the right channel is a problem also. Let's get the minus 15 volt problem fixed first and move on to the next one. Check the TO-220 low voltage supply. Thats where the 15 volts starts.

 

[laatsch55]

Interesting that between your two voltage checks the missing low voltage swings between the plus and the minus. Gonna have to ask Joe about that one....

 

[Northwinds]

Dan, hope your paying attention to this thread!!!!!!!!

 

[Danimal1969]

Dan, hope your paying attention to this thread!!!!!!!!

Yeah, I am. I read the whole thread this past weekend. It's honestly scaring the shit out of me. But st least I know there is help available.

 

[Northwinds]

If you can fix a Mercedes, I am sure you will be ok but its little slips or momentary lapses of concentration or getting too comfortable where bad things can happen. This is why I would not even attempt a PL. I have no problem working on guitar tube amps but SS well...

<iframe width="560" height="315" src="https://www.youtube.com/embed/_VrFV5r8cs0" frameborder="0" allowfullscreen></iframe>

 

[Gepetto]

Pad 1 0v 0v
pad 2 0v 0v
pad 3 -81.2v -81.2v
pad 4 -21v -24v
pad 5 -.5mv .2mv
pnp -22v -25v
pad 6 -1.2mv -150mv
pad 7 82.6v 82.6v
pad 8 -21.5v -24.5v
pad 9 -21mv -135mv
pad 10 -21v -24.5v
pad 11 82.5v 24.5v
pad 12 81.4v 81.4v

test points +15 15.6v
-15 -1.4v

Pad 12 should be NEGATIVE ~80V in both cases. Are these pairs of numbers L and R readings? Looks like you have a blown pico fuse on the one reading of PAD 11 reading 24.5V. That is the fused rail voltage coming from the backplane.

 

[nadude98]

Pad 12 should be NEGATIVE ~80V in both cases. Are these pairs of numbers L and R readings? Looks like you have a blown pico fuse on the one reading of PAD 11 reading 24.5V. That is the fused rail voltage coming from the backplane.

Pad 12 was negative... guess I was tired... had it written down in the notes correctly