(Topic ID: 224709)

Bally display showing random digits


By Brewchap

1 year ago



Topic Stats

  • 21 posts
  • 7 Pinsiders participating
  • Latest reply 1 year ago by Brewchap
  • Topic is favorited by 3 Pinsiders

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#1 1 year ago

I have two displays that at times show random digits. Most times I can power on the pin and the displays will be fine, but crap out during game play. Other times powering on the pin, the random digits are displayed. The problem also follows the display as I move them around. I have replaced the decoder chips and reflowed the pins.
I'm now at a lost on what to do next. Pinwiki only discusses what to do when you lose a digit. not when you gain a bunch.

#2 1 year ago

Connectors, connectors....

#3 1 year ago

Connectors is a problem with these pins, but the problem follows the placement of the displays, while the other displays are good as they are rotated. I would think that these would rule out connectors.
Thanks for the suggestion!

#4 1 year ago

Can you post a picture of the board? Use an ohm meter and check all your resistors for proper value, then use the diode mode and check your transistors.

#5 1 year ago

I have checked the transistors but not the resistors. I'll do this tonight.

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#6 1 year ago

Displays look to be in decent condition. Headers need to be cleaned up, one on the left needs reflowed and the one on the right has too much solder. Remove as much as the old solder as possible then reflow them. Then clean up the flux with some 90+% isoprople alcohol. If the resistors check within tolerance, especially the 100k (brown/Black/yellow ones) then about all that is left are transistors. Even when they check good in diode mode they could be breaking down under load. Do the same digits light up when it is acting up? We are taking digits here and not segments, correct? If the same digits are acting up then it is probably the digit driver/level shifter transistors. I typically change them both at the same time. Take a look at Steve Kupla’s page, http://stevekulpa.net/pinball/bally_disp6r.htm , for some more hints on troubleshooting these displays. They are not hard to fix once you get and understanding of how they work. Look at the schematic here, https://www.pinitech.com/retrofit/schematics/bally_as2518_58_7digit.pdf , if it doesn’t make sense ask questions.

#7 1 year ago
Quoted from TheWiz:

Remove as much as the old solder as possible then reflow them.

^^ This is important.

One thing you DON'T want to do with these is flow new solder over the old. The old solder is crap and simply flowing new solder over the top will result in a crappy connection.

#8 1 year ago

If you're going to remove the old solder then why not replaced the old header?

#9 1 year ago

If I were working on the display I would certainly replace the header because I have the .156” headers and a Hako desoldering gun so it takes me about two minutes to do with zero damage to the board, others may struggle with it, I know I did until I got my Hako. I also replace all the 100k resistors with 1/2 watt ones.

One other thing to check that I forgot to mention above is the high voltage. Make sure it is set around 170 volts.

#10 1 year ago

Thank you guys for your input! This will give me something to work on. I do have a Hako fr-300 to desolder with. I will make a list for GPE later this afternoon to replace the suggested components.

#11 1 year ago

I found 4 300k Ohm resister bad on one display and replaced them. They measured about 400k Ohm. The other display checked out good. I ordered the parts and they should be here some time next week.

#12 1 year ago

I checked the transistors and didn't find anything wrong. Connectors J1 and J3 have been replaced. and I also tried to adjust the display voltage from 190 to 170 volts but 190 volts is the lowest that I can set it using the pot.

I still dont understand what would enable the digits on a display that should be off.

#13 1 year ago

I would check out your driver board also. You should be able to dial that voltage down well below 190. Not going to solve your issue at hand, but may save you later.

#14 1 year ago

Did you run the self test on the displays?

#15 1 year ago
Quoted from JT-Pinball:

I would check out your driver board also. You should be able to dial that voltage down well below 190. Not going to solve your issue at hand, but may save you later.

I agree, I want to be able to take the stress off from the displays.

Quoted from jj44114:

Did you run the self test on the displays?

Yes, self test works great unless the digits go haywire. If it don't boot up with random digits, vibrations from pop bumper/game play, etc will cause they to act up.

#16 1 year ago

When I rebuild these old driver board I dial the voltage down to like 175. I know folks go lower but that is going to bring up the amperage on the circuit as the displays continue to draw for power.

As for your display issue as me as a plus one for connectors. I would replace the .156 headers on the displays. I would also repin the female side with Trifurcon style connectors. If you grab the connector with the game one and twist it slightly dose it act up? Be careful as there is 190v there.

#17 1 year ago
Quoted from JT-Pinball:

If you grab the connector with the game one and twist it slightly dose it act up? Be careful as there is 190v there.

No sir I gave them a pretty good twist and I also took an old toothbrush to tap around with. I also shook, bent, wiggled every wire and connector in the head to try and make it mess up. Best that I can do to make it mess up is to rap on the display "door".

Quoted from JT-Pinball:

As for your display issue as me as a plus one for connectors. I would replace the .156 headers on the displays. I would also repin the female side with Trifurcon style connectors.

Got headers and connectors on order.

Quoted from JT-Pinball:

When I rebuild these old driver board I dial the voltage down to like 175. I know folks go lower but that is going to bring up the amperage on the circuit as the displays continue to draw for power.

I may have to replace the pot. Turning the pot, it goes from 190 to 224 volts.

#18 1 year ago

I was having a similar problem. In test mode it would count 1-7 just fine then when it displayed 8 and 9 it would show random numbers. I thought bad decoder. I replaced the header and connectors and was about to replace the decoder but first i tried it again. The new header fixed the problem.

#19 1 year ago

My Fireball Classic was doing this and I found out the mpu was not making good ground.

#20 1 year ago

You have taken the same trouble shooting steps I would? Not to say that is all of them. I still would change the male header before I would go crazy. Dose it stay with the same digits or move around?

As for the driver board. I would look deeper into the circuit. My guess is you have a resistor out of spec. The pot is doing it job. Opinions vary but I just change the all the headsets rebuild the 190 and 5V and do mods to those boards pretty much right after I get a new game going. The 5V is critical to the game operating and bad 190v can damage displays.

#21 1 year ago
Quoted from phil-lee:

My Fireball Classic was doing this and I found out the mpu was not making good ground.

I've done a ground mod where I ran a wire to all 5 boards to ground.

Quoted from JT-Pinball:

Dose it stay with the same digits or move around?

Yes it stay with the same digits that it randomly chooses. Some time the displays show the same digits... sometimes not.

Quoted from JT-Pinball:

As for the driver board. I would look deeper into the circuit. My guess is you have a resistor out of spec.

I rebuilt the driver board per the Pinwiki web site but I will go back and check the resistors.

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