I had a fully working Gottlieb Chicago Cubs Triple Play. Not long ago the display went out during game play. I turned the pin off and restarted after waiting a minute or two. Upon turning it on, the display functioned normally. After a couple of weeks and many games, the display went out again during game play. This time after a reboot, the display would not function.

I have:
Checked all fuses - all tested good
Cleaned the connector traces and rest the connectors
Re-pinned the display connectors
I see no obvious problems on the display board ( burn marks or bad traces)
I switched out the power supply with a spare. The display did not work.

Any suggestions on what check/ do next ? The game isn’t nearly as much fun without the display.

Thanks,
Phil

Thank you for the suggestion. I will give that a try later today.

Ok, I am back at addressing this issue. Had to take care of some family business, which of course takes priority over pinball. Additional things I have tried are:

1. I re-tinned the boards edge connections. This did not help. Display still blank.
2. Double checked my re-pinnig and then checked continuity from connectors to circuits on the boards. All tested Ok.
3. I checked the continuity of all traces on the board and all tested Ok.
4. I tried using a logic probe but, soon realized I didn’t know what to expect so all the flashing lights and buzzing didn’t help me. I did briefly try to find data sheets for the chips, but was unsuccessful.

Any suggestion of what to try next? I can replace diodes, resistors, capacitors. I have not replace chips.

Thanks,
Phil

I am getting a solid 5v at the MPU. The correct voltages are getting to the display. I still need to confirm voltages on the chips on the board. I’ll report later

I didn’t think that the display was powered by 5v, but thought I would add that info in just in case as the power supply does provide 5vdc to the board.

I have read the information on PinWiki several times. I will read it again just in case I missed something.

Below is additional information. To be honest, I am not sure what all this is telling me. If you have questions or would like to see additional information, please do not hesitate to ask. Thanks again for your input!

This morning I got the following reading
From connector A4J1 (connector that plugs into the display board’
If I am reading the schematics correctly:
Pin 1 & 2 should read 6.2vac- I read 6.7vac
Pin 3 & 4 should read 32vac - I read 37.7vac
Pin 7 should read 5vdc - I read 4.9vdc

Z1(7417 ic) should read 5vdc at pin 14 - I get basically nothing 0.28dvc
Z2(7417 ic) should read 5vdc at pin 14 - I gat 4.9 vac

U1 & U2
Should show :
Pin 35 -45v
Pin 36 +5v
Pin 37 -15v
Pin 39 -15v
I am not getting a reading from these pins.

Capacitors read as expected except for C3 & CR4. These should be 10UF. C3 shows 357UF & C4 shows 0UF. These were tested in circuit with a Fluke 15b+.

From PinWiki “ The board rectifies 32VAC via diodes CR1-CR4 to produce -45VDC and -15VDC for use by the segment and digit drivers.“. I get a reading of 0.538v from CR1-CR4, in circuit.

I have repinned both those connectors. I checked continuity from score to on board circuit. All tested OK using continuity. I’ll go back and recheck. I have been known to make a mistake

Thanks for the suggestion.
Phil

Thanks Ed, I pretty much thought my reading were off. Most likely user error. I will try again.

In the mean time, I was able to borrow a working display and it works. So the problem is on the board somewhere. Now I just have to find it.

Phil

Alright, first lessons learned is not to try and do any meaningful work after midnight. Repeated my measurements after double checking the ground. Below are the results.

U1: pins 39-35 all showed values ranging from -45.6 to -47.6vdc
U2: pins 39-35 all showed values ranging from -44.6 to -46.8vdc
U3: pin = -15.6, pin 2 = +4.93, pin 16 = -46.7 (all Vic)

Z2 pin 14 shows +4.92vdc.
Z1 pin 14 shows +0.28vdc (Thought I would add that I do not see any visible traces or evidence of broken traces to Z1 pin 14 although the schematic show +5vdc)

As suggested I measured the voltage across the following capacitors:
C1 = -46.6vdc
C2 = 48.8vdc
C3 = -15.6vdc
C4 = +4.9vdc
C5 = 4.92vdc
C6 = 4.93vdc

I not sure what this telling me. Any additional suggestions will be great fully appreciated.

Thanks,
Phil

Apologies for the confusion. I had assumed that the numbering of the chips pins was:
1 8
2 9
3. 10
4. 11
5. 12
6. 13
7 14

Since I could not see any visible trace for what I thought was pin 14. Since I knew you and the schematics were correct in that Z1-pin14 it should have 5v, I looked up the data sheet. Much to my chagrin I had been measuring the wrong @#&§ pin. The following numbering is from the data sheet.
1 14
2. 13
3 12
4. 11
5. 10
6 9
7 8

When measuring voltage on Z1-pin 14, a reading of 4.93vdv was obtained.
Z2-pin14 measured 4.92vdv
Sorry again for my ignorance. I am learning.

G.P.E. “Most cap voltages look good but there is an oddity across C2.
C2 should read 7V from plus end of capacitor to minus end of capacitor but was probably measured from ground to ???.”
Response-Measuring again I obtained a reading of +7.57vdc

G.P.E. “What voltage do you get across R2?”
Response- -41.1vdc

What is next? Would this suggest that U1, U2, or U3 are in error? Other possibilities?

Thanks,
Phil

Thanks again for your help!!!

When I measure pin 1 from ground:
On AC I get a reading of. 3.27 VAC
On DCI get a reading of -41.1 VDC

When I measure pin 2 from ground:
On AC I get a reading of 3.27 VAC
On DC I get a reading of -41.1 VDC

I measure voltage between pins 1 and 2 for safe measure. This time I got a reading of 6.52VDC

Hope this makes since. When measuring from ground, my AC reading obviously do not match result in 6.5 ACV. Hopefully I am doing this correctly.

I have access to a display board that Boston Pinball Company makes that is a plug and play model with the exception of supplying a 12v power supply. It uses the 12v to power the leds in the display. I plugged this in after I repinned connectors A1J2 and 1A4J1. This board works as expected.

I am not a aware of anyone close to me that has a working system 80b display (Gottlieb MA-644 board).

I live in eastern NC pretty much in the middle of nowhere. Raleigh is approximately 3 away. Anyone out there with a working Gottlieb MA-644 display within an hour of Aurora NC?

A fellow pinsider loaned me a working Gottlieb display board. I plugged it in and it works as expected. Based on this and that the power seems OK on my display; I assume that one or more of the chips are bad. Does anyone have a suggestion for which one is likely at fault?

I bought a logic probe not long ago, but still am not sure what it is telling me.

I saw a video on YouTube on testing a chip using the diode setting on a DMM. Is this a valid method ( red to ground, black on a leg/pin; reading between 0.3-0.8 are good).

Thanks
Phil

Finally got up enough nerve to replace a couple of chips. I socketed and replaced Z1 and Z2. The display now works. Special thanks to G.P.E.