HELP! Rescuing Dad's old PL400 S2 (pics)

[lightfall]

Q106/Q206 ():
Pos lead on Base, Neg lead on Emitter--reading 0 volts DC. Pos lead on Base, Neg lead on Collector--reading 0. Neg lead on Base, Pos lead on emitter -- reading 0.59. Negative lead on base, Positive lead on Collector--reading 0.73.
Pos lead on Base, Neg lead on Emitter--reading 0 volts DC. Pos lead on Base, Neg lead on Collector--reading 0. Neg lead on Base, Pos lead on emitter -- reading 0.56. Negative lead on base, Positive lead on Collector--reading 0.65.

 

[lightfall]

I must have flipped those results vertically since the next set I was working on was flipped vertically.

It looks like you have the wrong transistor numbers for the test. Q102, 202 are NPN, and your test results reflect good PNP's....

 

[laatsch55]

Q106, 206 are also NPN's....

 

[laatsch55]

Q106/Q206 ():
Pos lead on Base, Neg lead on Emitter--reading 0 volts DC. Pos lead on Base, Neg lead on Collector--reading 0. Neg lead on Base, Pos lead on emitter -- reading 0.59. Negative lead on base, Positive lead on Collector--reading 0.73.
Pos lead on Base, Neg lead on Emitter--reading 0 volts DC. Pos lead on Base, Neg lead on Collector--reading 0. Neg lead on Base, Pos lead on emitter -- reading 0.56. Negative lead on base, Positive lead on Collector--reading 0.65.

106, 206 are the TO-39 big silver heatsinked transistors. They are also NPN's and your results reflect a good PNP test....

 

[lightfall]

Hmm..OK, well if I try read that another way I get wonky results. Since this transistor is not labeled, this is the only way it made sense to me, since the other arrangements yield one reading as .56 and the other as .38 and reversed 0 and 0.38 which doesn't appear to fit the PNP or NPN schemes.

106, 206 are the TO-39 big silver heatsinked transistors. They are also NPN's and your results reflect a good PNP test....

 

[lightfall]

Maybe I have tried to do too much today and I should get some sleep. What do you think I did wrong here? What needs to be done next?

 

[laatsch55]

I don't know. Are you accessing the leads from the back of the board, as in the solder side? Also the center lead on a TO-39 is the base...

 

[laatsch55]

Hmm..OK, well if I try read that another way I get wonky results. Since this transistor is not labeled, this is the only way it made sense to me, since the other arrangements yield one reading as .56 and the other as .38 and reversed 0 and 0.38 which doesn't appear to fit the PNP or NPN schemes.

In circuit you will sometimes get some funky reading in the reverse bias mode. What were the readings with the positive on the base and the negative on the emitter and then on the collector?

 

[lightfall]

Hi Lee, I took a break for a day and went to see the movie "Interstellar", but I am back and I think I have the correct readings now. I am not 100% that I did not mix up the emitter and collector but the results are consistent with what I saw before.

Q106/Q206 (NPN T0-39):
Pos lead on Base (center prong solder side), Neg lead on Emitter--reading .59 volts DC. Pos lead on Base, Neg lead on Collector--reading .387. Neg lead on Base, Pos lead on emitter -- reading NOTHING. Negative lead on base, Positive lead on Collector--reading .387 .

Pos lead on Base (center prong solder side), Neg lead on Emitter--reading .563 volts DC. Pos lead on Base, Neg lead on Collector--reading .387. Neg lead on Base, Pos lead on emitter -- reading NOTHING. Negative lead on base, Positive lead on Collector--reading .387 .

Here is a picture of what I am doing with the + lead on the middle base. I am calling the emitter the solder point just to the left of that tip and the collector the one to the right.

 

[laatsch55]

Correct. And those readings are good. It is starting to look like there may be no damage to the board. Which transistors have you NOT tested yet?

 

[lightfall]

I "think" I tested all of the transistors. I have NOT tested the op-amps, or the electros. I also have not tested the many small resistors on the PCB as you said to wait on those time intensive processes.

What next? I am anxious to work more on this thing!

 

[laatsch55]

think its time you built a Dim Bulb Tester. Have you tested all the diodes?

 

[lightfall]

also, no damage is great news! I am guessing the transistors would have been the first to go?

 

[laatsch55]

They seem to be the first victims, yes..

 

[ksrigg]

Was Interstellar good? I've been waiting for a good sci-fi movie, and the trailers look good. What did you think?

 

[lightfall]

What is your favorite guide for constructing the dim bulb tester? I will make that today.

Interstellar touched upon a lot of big ideas, in typical Nolan fashion. Spoilers potentially ahead but I will try to be vague: there are interesting science fiction challenges that are somewhat unique to this movie, which provide the motivation for the film and the interstellar aspect of it. Larger ideas of time and space have really unique presentations as well, perhaps worth it alone for seeing that. I would say that the average person who is not a man and not a fan of sci-fi might enjoy the movie less, since at times it can be indulgent in respect to certain things (a little like 2001 in that respect). It also focuses on some of the finer details of space travel which some people might find boring. However, the acting is spot on. On top of it all the soundtrack is outstanding (Hans Zimmer) and there is a big visceral/emotional/action aspect as well. A lot of the concept/art is fantastic, and the portrayal of AI I found particularly fascinating. All in all certainly worth watching, not perfect when you are nitpicking it on the second day in retrospect with your buddies, but it is a "good film". I liked it a lot and I will watch it again later on bluray with the volume turned up for sure.

Now, the diodes, I think I tested all of those for one way transmission.

 

[laatsch55]

Diodes need to be checked both ways. Just reverse the leads, should be nothing in reverse bias mode. Except 1. I know the number on the WO and PL14 boards but not that familiar with the PL36 board.

 

[lightfall]

I am trying to find the D13 diode now.

 

[laatsch55]

A dim bulb tester is ver easy to build. You need a lamp base, usually a porcelin type that screws down to a 4" jct box. You will also need a duplex receptacle for the amp to plug into. Wire it so one of the AC legs goes through the light filaments, putting the incandescent bulb in series with the load.

 

[laatsch55]

I am trying to find the D13 diode now.

D13 does not exist on the PL36 board. Just test every one on the board.