Jennings J400 - 3 liner - Stuck on Call Attendant

[ArcadeDanger]

Hi Folks, slot machine noob here looking for help.  I collect and repair 80s/90s arcade machines, I'm looking into this for a friend of mine.  It's actually in really nice shape so I'm hoping to get it working again.


Problem: Call Attendant light always on. Does not reset by depressing logic board reset or the side key reset.


Sometimes it turns on with the bell going off full tilt (sometimes bell goes off, sometimes it's silent). Can’t reset or otherwise stop bell ringing otherwise.


Ran through the setup procedure as per the manual. Removed logic board, turned on, and the LED lights up intermittently (sometimes nothing, sometimes 000, 223, 221, 999). Front florescent lights on. This should technically validate that 24VAC and 5VDC are ok. I’m measuring 4.89vdc at the backplane connector to the logic board. Measuring 4.85 at the LS74L04n toward the front of the board, so a 0.05vdc drop across the board.


Logic board looks good. The battery seems original - mild corrosion. Removed it, I read the machine should work ok with out it (just won't save state).


Dropping quarters into the machine drops them through as it’s in the Call Attendant state. Flicking the quarter switches does increment the quarter counters on the top right side.


What should I try next?  Thanks!

[ArcadeDanger]

Couple more photos for reference...

[Amechanic]

The first thing I would do it to clean the logic boards edge connectors with w pink eraser to make sure to have a good connection. You might want to do this to the other boards connectors.

[ArcadeDanger]

The first thing I would do it to clean the logic boards edge connectors with w pink eraser to make sure to have a good connection. You might want to do this to the other boards connectors.

I did do a cleaning of that board edge connector with Deoxit (works wonders on arcade edge connectors), didn't really improve things.


I reached out to Op-Bell to see if he has one of his replacement reproductions for the board.  Since the voltages are ok, its not likely that the problem is elsewhere, right? 

[Op-Bell]

Did it work?

[Badbaud]

There are some CMOS chips on the board that MUST have the battery DC voltage applied to them or the board will not work.Attached is a mod that can be done to power the CMOS chips without a battery.

[Badbaud]

Here is a color version of the mod.