Hi all! I have a problem with a pretty heavily routed Stern World poker Tour I just picked up.

Aside from multiple other small issues and a pretty bad playfield, I have an issue with lamp column 2: all lamps stay off and it looks like the problem is on the board (I get continuity from the board pins at J13 to each lamp in column 2.

Looking at the schematic, I suspect the problem to be either the transistor at U11 (VN02N) or the IC at U9 (74HCT273). But how do I find out which one is causing the issue? I only have a multimeter and my trusty ol' logic probe.

lamp_matrix (resized).png
schematic (resized).png

Any help is appreciated!

Can't believe it's been a year since I worked on this game. But yes, I was awfully busy and the game just sat in a corner collecting dust. Well, after a few nights of work, the game is now finally shopped out and back together with some new parts, plastics etc and looking and playing great.

But that lamp column #02 is still out.

Time to fix this once and for all. First a little correction: I mentioned U11 in my opening post but I meant to say U16. According to the lamp matrix, that's the solid state relay driving my column.

I have replaced the corresponding VN02N, but the problem persists. I measure no output at J13-P8 and the lamp column does not light up.

So I guess the next thing to look at would be the 74HCT273 at U9 that is driving my relay? I have a scope pen here, but I'm unsure which leg I should measure? The schematic tells me I should get a hi/lo on Q1 (pin 5 of the IC).

pin_5_on_u9 (resized).jpg

Am I measuring the right leg of the IC?

q1_pin5_u9_hilo (resized).jpg

My pen is blinking hi/lo. Does that mean the IC is okay?

Thanks. Yeah, I soldered in a new VN02N back in september last year. When that didn't work I kind of lost interest (and time).

Anyways, I'm gonna measure continuity from that U16 to all 5 of its connections, good idea.

Thanks guys. I did some measuring yesterday. First I measured continuity between the VN02N and all its connections.

Leg 1 to ground
Leg 2 to the left side of R140
Leg 3 to the other middle legs of U11..U15
Leg 4 to the left side of D39
Leg 5 to J13 pin 8

All checked out.

Then I measured R140 and R141 for resistance and these also checked out (values compared to working U11 section).

With everything measuring fine and a valid signal coming from U9 I was stuck again. Could my replacement VN02N have failed again? Well, since I had a bunch of VN02Ns laying around, I figured "what the heck" and cut off U16 and replaced it with a new one.

Guess what? It works!

So either I installed a faulty VN02N the first time (highly unlikely) or I destroyed it while soldering it in (possible)? Or it immediately short-circuited again due to something messed up under the playfield? And of course, then I did my playfield shopout (which had me remove all lamps from the playfield) before soldering in the second VN02N today. That's where I'm putting my money: my shopping out removed a short circuit lamp socket.

Who knows, but I'm glad it's working again - Time to ante up!