Are These Circuit Traces Bad

[DaveWM]

Originally Posted by TinCanAlley

The horizontal board gives me a known bad circuit that I can comfortable work with for practice.

The transistor from the NOS board is the exact same NPN as on the original board. I put the meter in diode mode and connected the positive to the base (the E, B and C are clearly marked on the metal tab). I connected the negative lead to the collector and got a reading. I then connected the negative to the Emitter and got a reading. I then connected the positive to the emitter and the negative to the collector and got nothing. I reversed the leads and got nothing.

I put that transistor back on the board, install the board and the TV won't fire up other than sound. If I take the transistor from the old board and put it in the new board, it works like a charm.

I guess I'll just let this one go. Since I seem to be doing it correctly, maybe there's something else wrong Maybe the sockets don't like the legs of this one (they are gold plated unlike the older, working one). Maybe it has a thing about flashy transistors.

Anyway, I'll just wait for the scope and my brother.

in the diode mode did you reverse the polarity after the Base to Emitter same for reverse the Base to collector? diode checks must be made both ways same on transistor, you must check base to emitter and base to collector BOTH ways.

[TinCanAlley]

Originally Posted by DaveWM

in the diode mode did you reverse the polarity after the Base to Emitter same for reverse the Base to collector? diode checks must be made both ways same on transistor, you must check base to emitter and base to collector BOTH ways.

Yes, I did the following:

Positive on base and negative on emitter and collector (readings on both)
Negative on base and positive on emitter and collector (no readings)
Negative on collector and positive on emitter (no readings)
Positive on collector and negative on emitter (no readings)

Those are all the possible combinations. Like I said, I have no idea why this one won't work, but I am confident I've tested it properly. Oh well, like I said. Maybe it's something about the socket.

[DaveWM]

those should be about .6v for a silicon transistor (when you got the reading).

[zeno]

DaveWM has you on the right track. Only thing I
will add is the 2 100K resistors are labeled 5% ( R201 & 206 )
and would be highly suspect. Also since you will
have a scope be sure there is NO crap on the 23.5v
( source #2 ). Should be pure DC.

73 Zeno

[TinCanAlley]

What would be nice is if they would label the posts for connecting the scope like they do the ones for calibration. All the points necessary for APC, Brightness Limiting and such are marked. Scope points would be nice as well. I'll be going under the chassis to note all the points, note their positions on the strips and then noting their positions on the top side.

This should make life easier and I don't have to keep the set on its side while I test.

[DaveWM]

did you ever get anywhere on this problem? the main things to look at and check if you did not scope would be that diode and those two voltage divider resistors )100k each, think they were banded 5%

[TinCanAlley]

Originally Posted by DaveWM

did you ever get anywhere on this problem? the main things to look at and check if you did not scope would be that diode and those two voltage divider resistors )100k each, think they were banded 5%

Well getting my brother over with his scope is proving to be a major task. I don't know when he'll have the time or desire.

I did manage to find NOS OEM transistors and the blanking diode. I also got my hands on the 1K, 33K and some 100K resistors, but I have a question about the 100Ks. The original 33K is a carbon composite (I believe from its shape and brown color case). The 100Ks look like standard film. I got my hands on the 33K replacement in the composite form. My question is about the 100Ks. I was given a few that are also composite, not film. Is it okay to use the composites as replacements? The wattage is the same. In the attached pics you can see the diode, 33K and two 100Ks in one and the 1K connected to the transistor in the other pic). Those are the ones I'm looking at changing.

So with the new transistor, diode and resistors I might just go ahead and replace them all. Of course this is after I replace the blue convergence coil that seized up. I managed to find an NOS replacement and it should be here Monday at the latest.