Ok.

So I removed J209 from the MPU, the ground shorts do not show.

When the 10 switch opto board (which I reworked and replaced the LM339s with sockets) is installed, power shows on the board, and in test mode, I show three rows with 'ground short'. Row 3 (White/Orange), Row 5 (White/Green), Row 7 (White/Violet).

When J3 is disconnected from the 10 switch opto, switch test shows those rows normal.

I've disconnected the trough opto board, but did not seem to affect the rows out.

Tracing J3-10 (the White/Orange wire, aka row 3), I show that there is no direct short to J3-1 (ground), and I show continuity to non-banded D3 diode and non-banded D12 diode as I would expect.

Because I show the entire row, and three of them, I am beginning to suspect something wrong with the LM339s as there are three. Don't have any good basis for this belief as I am lost here.

I don't show any short to ground or any continuity on U1 (LM339 # 1) from the white/orange wire.

I haven't tried to disconnect pin 5 (E2 Opto 3) from J2 to see if that's the possible short.

Looking for some insight, thanks in advance.

10 switch opto schematic 1 (resized).png

10 switch opto schematic 2 (resized).png

10 switch opto schematic 3 (resized).png

Thank you for that. I had some spare LM339s (new, from Marco's) and changed those out, same result. I double-checked continuity of the sockets from the solder side of the board, and even re-tinned some of the duller looking solder joints.

Originally this board was a real mess. I did socket all the LM339s. Replaced LM339s are TI LM 339 N.

I also replaced some diodes and 1/4w resistors on this board, and did some light trace repair.

Before the board repair, switch level/edge test was showing some very squirrely results - that part has cleaned up.

But right now I'm looking at rows 3, 5, 7 being closed/shorted. I've checked a few switches on the white/orange (row 3) and verified those that I've gotten to so far are operational, even clipping diodes, testing switches, soldering on new diodes - 1n4004s.

I know I will probably have to individually trace down all switches/wiring relating to these rows. Not my favorite thing, I'm kind of trying to avoid it! LOL.

I've done a bit of reading on the WPC games, and I think I can discount U20 being bad or the MPU (new Rottendog MPU, old U20) as when I remove J209 from the MPU (or J3) I do not see shorts on rows 3, 5, and 7.

It just seems to keep pointing back to this board. Admittedly I'm not certain.

I have the schematic, and a logic probe.

Any info on what to look for on this board?

TIA.

So, reading this - I would have the logic probe hooked up as follows:

Red lead of logic probe to pin 3, black lead of logic probe to pin 12....?

And the probe tip I'd be looking for high pulse on outputs 1-4 (pins 2, 1, 14, 13 respectfully)...?

This is going to be a real bugger to get power to the probe.

I assume I could get the power from pins 2 (+12vdc) and 1 from J3..

LM339 (resized).png

Ok, so with my Elenco LP 900, here's what I see.

LM339 number 1, U1.
Output 2, pin 1: High, Low, slow pulse.
Output 1, pin 2: Low, slow pulse.
Output 3, pin 14: High, Low, slow pulse.
Output 4, pin 13: High, Low, slow pulse.

LM339 number 2, U2.
Output 2, pin 1: High, Low, slow pulse.
Output 1, pin 2: Low, slow pulse.
Output 3, pin 14: Low, slow pulse.
Output 4, pin 13: Low, slow pulse.

LM339 number 3, U3.
Output 2, pin 1: Low, slow pulse.
Output 1, pin 2: High, Low, slow pulse.
Output 3, pin 14: High, Low, slow pulse.
Output 4, pin 13: High, Low, slow pulse.

I have test leads connected to pins 1 & 2 (ground + 12v) on J3.

Breaking it down, here's what I think it means:

LM339 1
Output 2 (pin 1): Square wave
Output 1 (pin 2): Logic 0
Output 3 (pin 14): Square wave
Output 4 (pin 13): Square wave

LM339 2
Output 2 (pin 1): Square wave
Output 1: Logic 0
Output 3: Logic 0
Output 4: Logic 0

LM339 3
Output 2: Logic 0
Output 1: Square wave
Output 3: Square wave
Output 4: Square wave

So, I'm unclear - what should I be measuring?

If I read (-) input 1 and (+) input 1 (pins 4 and 5 on LM339 respecfully), what should I be seeing on output 1 (pin 2)?

And I assume the same with inputs 2 through 4, and outputs 2 through 4.

Speaking to using the logic probe and not DMM.

TIA.

Ok, I don't think I have all the gear for that - I ran through one row last night (row 3), doing continuity and visual inspection of the switches, diode testing last night but did not find a short.

I'll go through row 5 and 7 today, but on the optos that didn't work, I'm not sure how to test them.

I'll look on pinside to see if there's a way to test the optos, maybe there's something there I can do.

I have a basic oscilloscope kit, but I don't know how to use it. That's on me, I know.

Ok, that's a plan. I have some extra LM339s also, let's see if there's any change.

Oh, sorry - it's been a while... Let's see if I remember....

Shotgunned the opto board, got it working by replacing the LM339s and U3, diodes, resistors that tested wrong.

Much of the issue boiled down to connectors and the MPU board. Replaced the MPU board, got it going again.