Yes, get that battery off and replace the 5101 with NVRAM so you don’t need any batteries. It is socketed, so you don’t need to solder. Just make sure you orient the chip correctly.

For future reference, Pinwiki is a good read for solid state machines. I haven’t looked lately, but there may be a section about the X & O light box. All else fails, do a google search or UTube search.

Looks like the Auxiliary Lamp Driver is responsible for controlling those lights. The text A9J2 on the schematic near the non-working lamps means board A9 (auxiliary lamp driver board) connector J2. From there, each pin on that connector is specified. For now though, try re-seating connector J2 on the lamp driver board. There's only 2 connectors on the aux lamp board, which I circled here: image-18.jpg

You can also try re-seating the other connector on that board and see if it helps. If anything, it may be a matter of re-flowing the solder to the header pins on the aux lamp board. I know I've had issues specifically with the ground pins on that board, flexing the connectors a bit with the game on would cause the non-working lights to come on temporarily...

Good luck on your first SS game!

JRC - I am guessing that there is re-pinning connectors and soldering the headers on the aux board in your future.

Those look like .156 contacts, KK series. Since you had to wiggle to get the lights on, I think the pins are likely worn out. You can either piecemeal them or do them all at once.

Great Plains Electronics used to sell the stuff you need, but Ed has retired. You will need crimpers, wire strippers, new pins, and likely a new header (on the board) to insure reliability. There are several threads here and many Utube videos on how to do this job. There are also several vendors who still have the pins and headers - again, do a search for Molex connectors and KK series pins.

It would not hurt to try and resolder the header on the board first - you may have cold solder joints - that is the easiest avenue to try first.

that is an IDC (insulation displacement connector) and IMO they are crap

if you're sure you want to change it, i suggest using a crimp pin type

you may just need to slide the black cover off and if you have the insertion tool great, but if not try pressing on the wires with a small screw driver, once you take the cover off you'll understand.

Didn’t realize those were 555 twist in lamps. Swap the lamp in the holders around and see if the problem stays at the socket or follows the bulb holders.

If wiggling the connector makes the lamps cut in and out resolder the pins. The solder tends to get cold over time, especially the pins on the ends.
Although the IDC connectors have issues, avoid replacing the connector unless you absolutely have to. The KK style replacements are becoming hard to get as they are manufacturer discontinued.

Yes, it's an intermittent connection as you have observed. Heat up the iron and reflow those pins. That's always the #1 go to in these games.

Does the MPU boot? There should be seven flashes on the led on the board.

Check the power supply fuses - you may have a blown one.

Check the voltages on the rectifier board test points. Check the voltages on the SDB test points

Check the voltages on the MPU test points.

Use Pinwiki Bally procedure for a step by step process on starting a Bally for the first time.

assuming your running gas displays, have you checked the test points on the player 1 display, ground, +5VDC and about 185VDC depending what you set the output at on the solenoid driver board?

It's a good idea to change the filter caps on the driver board, along with tying the grounds together for improved reliability. One of the caps on the driver board is the filter cap for the display voltage. The driver board takes 230v from the rectifier board and turns it into 190v to power the displays. Commonly I've seen resistors burned up and the voltage adjustment pot basically falling apart in the high voltage section.

If you haven't checked the solder joints on the driver board and displays you should do that as well. All Bally boards will have at least a few cracked solder joints each if they haven't been serviced. You should also verify the voltage at TP2 of the rectifier board, then TP2 and TP4 of the driver board.

Voltages: http://www.techniek.flipperwinkel.nl/ballyss/rep/index1.htm#tp
Ground mods/upgrading driver board: http://www.techniek.flipperwinkel.nl/ballyss/rep/index1.htm#cap
Cap kit for driver board: https://www.arcadepartsandrepair.com/store/pinball-kits-parts/pinball-kits/bally-as-2518-22-solenoid-driver-pcb-105c-cap-kit/

Your voltages seem ok, 173VDC is on the low side but it is preferred by some as it keeps the displays alive longer but puts stress on the 2 transistors in HV section. I learnt that from Quench

The commands and digit enables etc. come from J1 on the mpu board. You could try sliding the cover off and pushing on the wires in the pins?
Also checking the rear of the mpu board where the headers are soldered, looking for any dry joins or you could reflow them all, time consuming but worth it.
Also what condition are the pins like in the headers on the mpu board?
I did mention earlier, but I hate IDC's as a connector, but it's possible some of the pins have lost their tension and are causing an intermittent join to the header pin?

You could also try reseating or even swapping U10 and U11 on the mpu board, making certain you replace them with the notch on the PIA to the left.

Or before all that, with the game on try wiggling the J1 connector on the mpu board carefully side to side and looking through the rear of the backbox door at the displays you will see if they come on or not?

More things check:

Make sure your ground to the displays is good. You should measure zero volts at test point TP3 on the displays.

When you power on the game, after the last LED flash on the MPU board the LED should then go dim and say that way. Does the LED go completely off when you lose displays?

If you have a logic probe, probe the display blanking signal at pin 6 of U14 on the MPU board and then downstream at any of the displays at pin 10 of the display connector. From memory it should be mostly low with high pulses.

Yes a faint glow is fine.

You probably have a bad connection at the J1 pin 10 position which is the display blanking signal.
The connector housing has a black cover over where the wires are inserted. You can slide the black cover up or down to remove it and see how well the wires are holding in the connector. Post a picture so we can see.