BIG problems

[laatsch55]

And after that be prepared to have your ears peeled back and slammed back into your chair. The difference is that pronounced.

 

[laatsch55]

OK, checked in and out of circuit, got ya. I`m debating whether or not to replace D 14,15 since they are already "half out" and nasty looking, same with D 13, looks to be of the 1n4148 variety

Now you have touched upon a quandry we folks who fix these run into everyday. When I White Oak a PL for ahy Phoenix member I guarantee it for as long as I'm able to get out of bed and breathe. So, if the components that are not included in the upgrade are substandard what do you do, how far do you go, and who should be responsible for the non-upgrade failures?? I always had a problem with the fine line folks so I put my fortune where my mouth is---- if it fails for any reason, other that being picked up and thrown 5 miles away by a tornado, send it back and I'll fix it, for free, just split the shipping

 

[Phase Linear Phanatic]

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.

Gee Jerry? WHO might have had that one I wonder?.................

 

[Skratch]

Anyone who has an old Phase linear and likes the looks only will be very surprised what the sound quality will be after doing a WOPL makeover. 40 years later with the technology and expertise that this forum has it will stand up against any KRELLor MARK LEVISTON at a very small investment. These things have become bulletproff and you will be able to give them to your grandchildren.

 

[laatsch55]

Michael, I moved your thread over here. this is where we generally post out fixit threads. The PLWO section is mainly for reference on all things PL and White Oak.

 

[Michael F]

Driver board Diode testing

Got around to some in-circuit testing. These values are both Left and Right channels.
First off, D13 checks out well out of circuit and measures 79R (.05v) in-circuit, forward and reversed biased, does that sound right?
Left channel D9 is shorted.
D1,D2 wired back to back measure .575v, good?
D4,D5,D6,7,8 , measure .575v forward biased and 1.45v reversed, good?

Sorry for the dumb questions, rest assured, there will be more

 

[Michael F]

And after that be prepared to have your ears peeled back and slammed back into your chair. The difference is that pronounced.

I would be most pleased if this didn't happen first

 

[laatsch55]

D1, D2 one leg of 1 has to be pulled. D4, D5 are in serie. Individually they should be in that .575, measuring both should be double that. Should not have a reverse measuremt. D6,D7,D8 are also in series. same goes for them.

 

[laatsch55]

I would be most pleased if this didn't happen first

We'll get there.

 

[laatsch55]

D9 is part of the protection circuit, that 's one that goes with a major output short.

 

[laatsch55]

How about q1-q10??

 

[Michael F]

D1, D2 one leg of 1 has to be pulled. D4, D5 are in serie. Individually they should be in that .575, measuring both should be double that. Should not have a reverse measuremt. D6,D7,D8 are also in series. same goes for them.

I`ll pull 1 leg of d1 or 2 and remeasure
D4 and 5 In series, forward biased is still .575. In reverse bias is now 1.1v
D6,7,8 series forward bias 1.204v and reverse bias .6v

 

[Michael F]

How about q1-q10??

I need to finish with the diodes first

 

[laatsch55]

Ok, the reverse bias on D4,D5 is probably coming through R 14, a 3.3k resistor that parallels those 2 diodes.. Q8,Q9 are germanium transistors and in circuit will test around .110-.120, out of circuit around 250.

 

[laatsch55]

The reverse bias on D6, D7, D8 is probably coming through the BC junction of Q6, the bias transistor on the back wall in the small P strap.

 

[laatsch55]

Do you geta reverse bias through D5,6, and 7 when checking reverse bias individually?

 

[laatsch55]

Just giving you some things to check if I'm not around when you are...

 

[Michael F]

Do you geta reverse bias through D5,6, and 7 when checking reverse bias individually?

If you meant D6,7,8 then no, there no longer is any reverse bias readings out of circuit.
Same thing for D1.2.3.4.5
Replaced shorted D9, measures well in FB however, RB is 1.2v (in circuit)

 

[laatsch55]

Yep, due to all those matrix interconnections..

 

[Michael F]

Yep, due to all those matrix interconnections..

Forgot to mention, that's not the case with it`s Right channel counterpart