Hi guys.

I have an interesting issue which I am having trouble diagnosing. The diverter in my Judge Dredd stopped working. I tested all of the basic stuff (wiring intact, coil voltage, fuses) and realised that the transistor that drives the coil (TIP102 at Q54) was out of spec. So, I replaced it, as well as the predriving 2N5401, and the resistors between them for good measure. I reinstalled the board, but the diverter still didn't work. I rechecked my soldering and verified all traces were OK. I checked the new transistors and resistors, and they are all in spec. What the hell? I double checked the wiring by manually grounding the transistor, and the coil fires as it should.

So, I go into test mode and set the diverter on repeat (coin door closed). I can see the output of U4 (pin 5) pulsing low when the diverter is supposed to close, and the input (pin 4) remains high as it should. So, the correct signals are getting to the transistors, but they're not firing the coil. Then I double checked a similar input and output on an adjacent IC (pins 4 and 5), and the results were the same. I can see the collector of the 2N5401 go high when it should. The last part of the chain is the TIP102 which is supposed to go low but I haven't verified that yet. What is the best way to do it? Do you just put your logic probe on the tab of the TIP102?

I am at a total loss here. Any suggestions?

Side note: R92 is listed as 2.7k ohm in the schematics, however all of the other resistors on the board appear to be about 2.1k ohm. Is this an error in the schematics?

Yes, diode is good.

BUT! I think I just found the issue. On closer inspection of the board, it looks like the trace from the TIP102 emitter is actually severed. The failure of the previous TIP must have blown it out.

image (resized).jpg

I know, that's after I removed it to get a better look lol.

Diverter is now working after the trace was repaired. Guess this thread turned out to be a bit pointless but it forced me to work through the issue methodically at least!