(Topic ID: 247349)

System 80b display went blank

By BleacherBum

68 days ago

Topic Stats

  • 23 posts
  • 6 Pinsiders participating
  • Latest reply 50 days ago by BleacherBum
  • Topic is favorited by 2 Pinsiders


Linked Games

#1 68 days ago

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.


#2 67 days ago

Repinning is ok, but did you also check the board-connector? Often there are marks/wear of the previous connector, best to resolder them so they are smooth again (don't add too much solder as they ma become to thick.

#3 67 days ago

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

1 week later
#4 57 days ago

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.


#5 57 days ago

I had a dead one recently with lots of cracked and broken connections from the the glass display to the pcb. The double stick tape lets go and the glass displays flop around until the connections start cracking. I managed to repair it and get it working minus 1 segment being out. I had another display with one glass working and one dead same thing broken connections on the display glass.

#6 57 days ago

Swap the display with a different one in the game and see if the problem stays or moves.

Nevermind, I should have looked at the game to realize it uses a single display and not separate ones. You said you swapped the power supply, is there voltage?

#7 57 days ago

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

#8 56 days ago

The display isn't powered by the 5v.

#9 56 days ago

I haven’t worked in system 80b displays, but have you read any articles on pinwiki?

#10 56 days ago

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.

#11 56 days ago

From the pinwiki.

The best recourse is to repin both A1-J2 and A4-J1 / 1A4-J1.

From my experience with Gottlieb's, the boards are rarely the issue, it is almost always the connector or the connector pins.

#12 56 days ago

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.

#13 56 days ago
Quoted from BleacherBum:

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+.

Something really wrong with the measuring.
First -- Z1 pin 14 and Z2 pin 14 are connected to each other. One having proper power but the other not points to a broken trace.
However U1 and U2 showing No power at all indicates the meter's power lead was probably to a wrong place or not making good connection.
Try these again but make sure the meter is well grounded.

As far as C3 and C4 measurements - you measured these in circuit so you are measuring capacitance of other 'things' mounted in parallel. Can't reliably measure these in circuit.

Measure voltages across C1 and C3 to see if -45 and -15 are ok.

#14 56 days ago

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.


#15 55 days ago

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.


#16 55 days ago

There is definitely a broken trace or bad solder joint in there somewhere. Z1 pin 14 needs 5V at pin 14.
C6 is Z1's bypass capacitor -- C6 has good power, Z1 does not. Follow trace from C6 to Z1. Are you measuring this at the actual IC pin? If so, could be a bad connection between pin 14 and an IC socket (if Z1 is socketed).

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 ???. What voltage do you get across R2? This will tell us the offset voltage going back to your transformer.

#17 55 days ago

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?


#18 55 days ago

Much better.
The voltage measurements all look good. A tad low for the 5V but shouldn't be an issue.

Voltage across C1 should be same as voltage across VR1 plus voltage across R2:
Vc1 = -46.6
Vvr1 + Vr2 = -(7.57 + 41.1) = -48.68. So we're close enough.

Last thing to check for voltages would be to make sure the offset voltage is getting all the way *back* to the transformer.
This one would much more difficult to determine if you measured it at the transformer but you might be able to determine this on the 6.2VAC input. When measuring the AC voltage directly between pins 1 and 2 - you should get about 6.2VAC (you measured 6.7VAC as you mention above so we're good there).

BUT when you measure the AC voltage from ground to these two pins - the AC voltage should be offset by -41.1V (VCO).
With one meter to ground - measure the AC voltage at pin 1 and then from ground to pin 2 of the connector.
Downside to this is some meters will only measure the AC content resulting in 6.2V (6.7V).
Some meters will display not only the AC content but the offset as well.
If your meter only measures the AC content of 6.2V then try measuring in DC setting. Yes - this will fluctuate but will center at the VCO voltage.

#19 55 days ago

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.

#20 54 days ago

Yep, you're fine with those readings.
Well... that says all voltage to and on that board are good.

Next step says borrow a board if you can and try it out.

#21 54 days ago

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?

#22 53 days ago

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).


#23 50 days ago

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.

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