I have recently been working on a Bally Strikes and Spares that a new customer brought to me. His family has owned it for more than 30 years, and the past 18 or so it's been in storage. Upon setting the game up, it looks to be in very good shape, although it does have some playfield wear, it's fairly minor. The boards all look to be pretty good, and someone has already redone the power supply connectors, although they didn't do the pins, as those for the GI are already burnt, and will need to be rebuilt again.

Fuses have all been checked and are good. Voltages at the boards are good. MPU booted up on the first try! All self-tests passed except for two solenoids, and one display. Those issues have been rectified already.

The one issue that has me a bit stumped (haven't ever seen this before) is that the switch self test, shows only "01" on the display. No other switches will register whatsoever, and yet, the game was essentially playable with switches registering normally when I started the game up. There were initially only 10 credits on the game, and I was never able to put more credits on, even though I had the MPU dipswitches 17, 18 and 19 set to ON for a max of 40 credits. I swapped in my Altec Ultimate MPU and had no problems with the coin door switches registering in switch test, (worked just fine for the rest of the switches as well, no crossed up or stuck on). And credits would accrue correctly when the coin door switches were actuated.

But the original board after playing 10 games with no apparent switch problems, (other than the coin slot switches) no matter what I tried would not allow credits to be put on.

I set all the MPU dip switches to OFF and pulled connectors J2 and J3 after putting the game in switch test, and used a jumper to check from J2 pin 1 and the rest of the pins to see if it would register each switch.. Absolutely nothing would register in the display except for "01" No change whatsoever with dipswitches in the ON position either.

It's as if switch 01 is locked ON, (it's the middle rollover in this game BTW) and of course it's fine on the playfield. When the connectors were pulled, there was no change to the status on the display. The Ultimate MPU had no problems whatsoever, and showed no faults. And yet the original board has no corrosion, boots perfectly every time and played correctly with the 10 credits that were on it as I was going through it. Oh, and yes, I swapped the PIA's with no change either.

What could cause this behavior? I'd like to try and keep the original board if possible before going ahead and spending 200 bucks on a new Altek.

Anyone have a suggestion?
I could use them.
Thanks!

Board has no corrosion, battery was replaced with memory cap some time ago. Tried reading pins with MPU dipswitches in both OFF and ON positions, so no change there.
No coin switches register, and this is with both J2 AND J3 off, so again, no change.. (coin door switches go through J3 if I recall, J2 is for the playfield). Checked pins, but did not reflow yet.
Have not checked diodes or caps on switch columns, but there are quite a few "clipped" disc caps from switches on the playfield I assume, didn't check all those yet, so I could see how there could be a bad one or two on the MPU. due to age.
Yes, I have a logic probe, but haven't tried checking the lines with it yet.
Original Scanbe sockets still installed on this board. Tried reseating both PIAs, plus CPU and RAM chips so far, with no change.

If dirt etc can cause issues in the dipswitches, can some contact cleaner help here?

Also, BigAl, the coindoor switches themselves are fine, as demonstrated by a flawless operation with my Altek board... so it's somewhere on the original MPU that the problem lies.

With all dipswitches OFF, and in attract mode, All pins are HIGH except for pin 5 which is low, pin 7 has no output (assuming this is ground) and 8 through 15 are also all HIGH

In switch test (still all dipswitches OFF, and both J2 and J3 pulled after getting into switch test) Pin 8 is HIGH, 9 through 15 are pulsing High/Low

I'm guessing you're going to tell me that there's a component on line 8 that's bad.. probably a resistor or capacitor. Waiting to hear back first though.

Looks like one of the disc caps is out of spec.... reads twice as high as the rest, and it has some surface damage as well. From what I can see it's also on Pin 8's line. I'll see if I can pull one from a spare board and post back with the results tomorrow.

Quench, measuring the resistance between pins 8 and 15 and ground each reveal a reading of 55 to 56K Ohms, except pin 8 which reads 1.2M Ohms!

However when checking the resistance of each resistor itself, I get a reading of 1.2K Ohms including R47 on Pin 8's line. Not sure what to make of that. Solder joints all look good, but I'll start with reflowing those first and rechecking readings.

I'll also try just removing one leg of that suspect cap and see if that changes anything since I'll have the iron out

R46 checks out at exactly 56K Ohms, has continuity on both sides (one to ground, the other to dipswitch 1).

Checking continuity from CR42 on the other side of dipswitch one is also good. As is continuity from CR 42 to R 46 when switch is on/closed, and no continuity at these points when switch is off/open. So these components and the switch all look good, as do the traces. Again, this board has no signs of corrosion at all.

Bally board 1 (resized).jpg

Bally board 2 (resized).jpg

Pulled the dip switch pack, removed the old "repair" checked each dip switch for continuity in ON position, found all 8 switches working properly.
Resoldered to board and checked for continuity from CR39 through CR42 to corresponding dip switch and then through to each corresponding resistor on the other side... R43 thorugh R46. Each worked correctly and had continuity with dipswitch in ON position, and no continuity with switch in OFF position. So the dipswitches at this point, don't appear to be the problem.

I pulled R47 and swapped it with another resistor, no change
I pulled C19 and swapped it with an axial cap from another board. No change.
But after reinstalling both the original resistor and capacitor to the board, I no longer have ANY resistance reading from J2 Pin 8 to ground. It WAS reading 1.2M ohms before I pulled the components.

So I checked continuity from every single part as follows:
J2 Pin 8 to R47 GOOD
Other side of R47 to C19 GOOD
Other side of C19 to C30 GOOD
Other side of C30 to CR4 GOOD (CR4 also tests good in diode test with null reading one way, and .54 with leads opposite)
Other side of CR4 to PIA U10 pin 6 GOOD.

What am I missing?

yes, swapped again, no change.

One thing of interest however. When testing for resistance between pin 8 of J2 and ground.. I get an "O.L" reading with black lead on ground and Red lead on pin 8, but reversing the leads gives a reading of 18.3M Ohms. Obviously this reading is roughly 56K Ohms for all the other pins 9 through 15 no matter what the orientation of the leads. Any clues why this would be?

Ok Quench, getting somewhere now.

Continuity from R47/C26 to U10 pin 10 is good.. but NO GOOD from R46 dip switch 1 side to U10 pin 10. I'll wire in a jumper and see what happens next.
Fingers crossed.

Ok Quench, one jumper later, and resistance at Pin 8 on J2 is the correct 56K Ohms, and game is now working properly!

Obviously I'm working without a set of schematics, something I don't usually do. So thanks for your guidance and help. I definitely couldn't have gotten this fixed without your help on this.

So to reiterate, the issue ended up being an open connection from the junction of R46/dip switch 1 to U10 pin 10. Don't see the trace that connects them, so I can't see where it's out, but once I added the jumper, everything cleared right up. For the record, it appears that the original U10 socket has never been worked on, but the dipswitch 1 block has definitely been taken out (poorly) and worked on, so I'm guessing that the junction is somewhere in this area that it was lost.

End post.

"If they messed up traces on a simple job like DIP replacement, who knows what's under there......"

Hit it on the nose Vid1900!

ooops.. sorry bout that. Edited above.

Thanks again Quench, I'll be sure to check that link from switch 1 to 9. Again, couldn't have gotten this up and running without your help. I very much appreciate the insight.