Had this machine working earlier in the day pretty reliably for several hours. Went to try and tighten up the flippers (with the machine on) and grounded one of the flipper input connections to ground. Immediately, the Rt Eject hole started pulse firing. It does stop when the machine is put into test mode, and passes the solenoid test. Anytime the machine is in attract mode it repeatedly fires on/off. Game will no longer start either. Tested the associated transistors and the resistance looks good on them. Thoughts?

Thanks for the replays! Unfortunately, its not a stuck switch, I did check that already. I'm still having trouble properly reading the switch test, I can enter it into the mode and see a few coordinating numbers cycle through. The switch matrix chip logically would make sense, as it is not being held in an engaged position (like I've seen with a bad diode), put rather cycles between on-off-on. I did take a quick glance at the machine and it looks like my switch matrix IC is socketed. Is there a replacement chip I can get or is it something that is machine specific? (Mine is a 6821, I'm guessing if I can find a replacement it'll be a drop and go)

Edit: Did some searching and looks like the 6821 is just a normal IC I can get through various resources. Looks like I am off to order parts, thanks! I'll report back with results.

I really appreciate the help guys. I think I have down what we are discussing. I can go ahead and order new ICs for those locations, they are cheap.

I do have more of a logic/troubleshooting question. So my understanding is the switch matrix is split into rows and columns, and each row/column have a dedicated IC. So, if I were to put the machine into a switch test, I would theorize that I would see a large number of switches showing as activated in the rows 5-8 on the matrix? Am I understanding this correctly? My guess is since we are thinking I shorted the lane change switch (5/6), it is affecting the right eject hole (6/4). So, logically, it can't be either of the column ICs as the two related key pieces are controlled by different ICs, but leaning towards IC16 as both key pieces reside in Rows 5-8.

I appreciate help with the logic, as I would rather learn the "why" rather than asking for help and getting the "change this" answer as it eventually leads to less dumb questions on my part.

I'll check the coin door once I get home... Darn work.

Yes, I do own several DMMs, all with diode mode.

Unplugging the coin door has no effect, eject hole continues to fire repeatedly regardless.

Any thoughts as to what to test next, or should I just replace the PIA and switch matrix ICs to see if that just resolves the issue?

Swapped out the PIA's at IC5 and IC11, as well as swapped IC15 and 16 with new chips to no avail. Didn't have any n7406 chips to try at IC17 and 18. Anything else I can test/try?

Dang, still no dice. I did the diode test on ICs 17 and 18, and all inputs to ground have the proper resistance. Could the issue be in ICs 1-4?

Thanks for the replay Yetti, I will give it a try when I get home from work and report back.

With 2J3 disconnected, the eject hole firing stops completely. Once it is re-connected, it resumes "kicking" repeatedly.

Thanks for confirming IC 1-4 are working OK. Just for giggles, I disconnected 2J2 and the issue stopped just like it did for 2J3. I'll go mess around with the switch test and see if anything jumps out at me. Just a quick question though.. When I do my switch test, several numbers will cycle once. Is this telling me anything important? Some I know should show up (like the ball trough), and others seem unrelated to the issue. What would a "good" test look like?

Switch test results:

2 (Ball Roll Tilt), 12 (Left Kicker), 18 (2 Target), 26 (top left jet bumper), 42 (right kicker), 50 (Lower Middle Left Standup), 52 (N/A)

All of these correspond to Row 2, replaced IC15 again (started losing a few pads at this point) and soldered the top of the board traces to the legs.

Same problem, 3 different chips at IC15, so that can't the the issue, can it?

OK, I'll order a few replacement chips and try replacing IC17/18. I actually did socket it on the 2nd attempt, but thats when the pads started lifting. To make sure I had good connectivity I removed the socket and placed the chip in and soldered the top of the board where the traces were.

Thanks for the help Schwaggs, I swear I am losing hair over this machine, and I'm not working with much to begin with.

Finally! OK, so I replaced IC 17, gave it a try, no dice. Tried to replace IC 18 just because it was already socketed. Bam, back to working again (for now). Still have 2 displays with 1 segment out, but at least the machine is playable again. For the first time in 8 months, my wife will be able to play it for the first time. Thanks everyone for your assistance in figuring this one out.

Probably easiest if I post a pic. Here's what it looks like. It does occasionally clear up after it warms up a little.

20160813_100135_(resized).jpg

OK, so a little more info...

Sometimes the displays work OK, sometimes (most often) you see the picture above, and other times it looks more like a 7. So there is obviously something going on that is somewhat intermittent. I have the IC version of the master display board. Using the pin-wiki as a guide, I checked all of the resistors on the right side and found one that was bad, and replaced it with a 1/2w 10k resistor. I figured I'd give it a try again, but the issue persists. I plan on pulling the board out again this evening to check the resistors on the left side. IF they check out OK, Then I need to move on the the ICs and check them (according to the pin wiki). Any suggestions on which IC to start with? Also, if it is determined I need a replacement IC, who is the best supplier? (I am currently assuming its a UDN6118, but will confirm a little later).