Helping a friend with some issues on his new Rolling Stones. When purchased, he played 3 games with no issues. Upon bringing it home, it ran thru the self test once with no issues, but then coils stopped working in test mode and in game play. At this point the only coils that work are:

#8: Saucer
#12: Drop "D"
#13: Drop Reset
#14: Coin lockout
#15: Flipper relay
#16: Saucer drop

I have rebuilt the rectifier and did the recommended mods to the Solenoid board (new headers, ground mods, note it is a Stern SDB-100 rev C) and board tested the individual transistors. Power is ok at all test points. He has also repinned the 0.156 female connectors for both rectifier and SDB (pushed wires in again on the 0.100 IDC connectors). Have verified 43VDC at all coils, appears to be an issue with the ground circuit. Also, the coils fire correctly when the tab of the individual transistors is grounded to the ground braid?

Any thoughts on what to check next? I'm assuming it's either connector to/from the MPU or a bad IC, but looking for specifics on where to look and how to test.

Thanks, I definitely would want to do that, but don't have the housings on hand to do it right away. I strongly suspect the connectors as well. Looking at the schematics, the likely culprits would seem to be pins 3-6 on SDB to 1-4 on the MPU.

I haven't looked at the MPU in person, any chance this type of behavior could be from loose chips there?

None of the working coils seem to fire more than once during the test. While repinning the connections is definitely on the "to do" list, the behavior has been pretty consistent despite many efforts to clean/reseat the connectors. Initial thought would be the behavior might change after reseating. Are there any other components to check while waiting on the housings to repin those connectors?

Is there a site that has the list of which solenoids go to each of the control chips on the SDB?

Doh, I completely missed the U numbers on the pretransistors. One coil is working on U3, the rest are U4 and most continuous. So it looks like only 2 momentary solenoids are actually working. Starting to suspect a chip went when it stopped booting until the rectifier was repaired.

Cool, yeah, they were tested according to Clay's guide with the DMM. Pin 1 and 4 of U4 were OL (those aren't connected per above), pins 5 and 15 of all of them read 0. The other pins were either 0.7V or 0.2V, so at least from that test they appear fine. Trying to test the 4 wires coming from the MPU, but they seem to strobe too fast for the meter...and then doing the ground test of the individual transistors the playfield fuse blew and he doesn't have a replacement on hand.

Suspecting the decoder, I had him swap the SDB with his KISS. The coils work correctly with the other board, so I'll replace the chips, and I expect that will take care of it. Thanks all for the help!

Thanks for the input, yes, the coils were checked for 43V input, and work when the transistor tab was grounded.

I did just replace the headers on the SDB (after the issue began), I suppose I could have messed up a joint, or a trace is fried, I should double check for continuity on the board between J4 and the decoder prior to replacing. As mentioned, the other SDB had the coils working fine, so the issue is definitely limited to the original SDB. We tried to probe the wires at J4, and saw some 5V switching there, but the DMM he had was pretty slow at picking up changes. The other thing I want to check before pulling the chips is that there is a good 5V on the original SDB and the MPU...I think that would be the only other thing that could be different between the 2 SDBs...unless of course all the drive transistors board test fine but don't work in application

An update, after investigating which coils work, the coils corresponding to the first 6 transistors work, at the 7th a trace has lifted. I assume this is the grounded leg?

IMG_20220127_195437_01 (resized).jpg

I can confirm that was the issue. I did also notice the other spot it was lifting and reinforced that as well. It seems as though the copper just pulled away from the board, I'm assuming due to flexing.

Thanks all for the assistance