Finishing up a Bally Xenon for Expo. All issues were gone, and had everything working. Decided to replace the ratty power cord. On first power up after that (several quick power cycles due to crappy power strip connection), 23 (maybe more) of my playfield controlled lamps are out! This also affected half of the surround lights (numbers 5, 6, 7 & 8 on all four sides). There may be some more on the backbox - I did not note every one, but most of the playfield is correct.

I did check several of these - they all lit fine when grounding the lamp board transistor's anode. That would seem to indicate a bad transistor - but not so many of them at once! Plus, there are lights out driven by the Aux Lamp Board too.

So, it must be upstream? It is not just one decoder out - there are outputs from every decoder leading to the lamps that are out. I made a quick chart with lamp, connector & pin, transistor number, and decoder and channel. See below. But I am not seeing a logical pattern yet - but maybe one of the address lines feeding those decoders? Maybe back to the MPU?

Anyone seen something like this? Full disclosure - I did do some soldering on some of the lamp sockets, but everything was OK until I shut down to replace the power cord. I have scanned for potential solder splatter, but have not found any yet.

Thanks in advance!

Xenon Lamps Out Chart (resized).png

Thanks, guys!
I just got the chance to try out Quench's suggestion. Starting the game with J2 & J3 off the MPU, all the attract mode lamps were lighting! (except the 30K Side Saucer, but that might be a different issue).

I tried it with J2 plugged in (J3 still out) with the same result.

I had earlier clipped 3 switch caps on the the 4 button switches on the arch to get switches 3 & 4 there working. I did not have replacements, but will have them when I get there. So there could be a solder blob somewhere on the playfield, or a diode or cap shorted?

Since you mentioned Strobe 0, might that narrow it down to the cabinet switches marked with ST0? Credit Reset, Tilt? I will take a look around those areas.

Matt

SUCCESS!!
I went around the cabinet to the cabinet switches using ST0. The tilts were all OK, but then I saw the credit/start game button. I had changed the lock to a new one, and the old one was stubborn coming off. I was cranking on the large nut with a crescent wrench.

Well, the diode on that switch was resting up against the coin door metal! After pulling it away from there, and reconnecting J3, all the lamps are working again! (well, except that 30K lite, but I will look at that at Expo...I am loading the game in my car tonight)

Thanks so much for the spot-on insight! I did not know about that ST0 sharing between the switch and lamp matrices.

Many thanks!

Matt