(Topic ID: 186411)

Williams System 3-7 Display Segment "C" is gone on Players 2 & 3

By bdPinball

6 years ago


Topic Heartbeat

Topic Stats

  • 13 posts
  • 4 Pinsiders participating
  • Latest reply 6 years ago by bdPinball
  • Topic is favorited by 2 Pinsiders

You

Linked Games

#1 6 years ago

I have a Laserball and Segement C is missing on Players 3 & 4. I looked at the diagrams, and I read on line that the first thing to check is the R1-R7, and sure enough the resister was physically blown - Not connected. I replaced that (and the rest of them too) but unfortunately segment C on 3 & 4 still doesn't lite.

Thanks guys.

-Brian

#2 6 years ago

You may have a lifted trace. Hold the PCB up to a very bright light so you can shine the light "through it" to see if a trace is broken.

You can also check each segment/trace with a meter. This recently happened on my TAXI machine when replacing one of the resistor networks. Took me 30 mins to find a hairline crack in one of the PCB traces.

#3 6 years ago

Check the traces but you are probably going to need new displays or glasses. Unplug machine and move the bad displays to player 1 & 2 and see if the problem follows. The lifted resistors are probably burnt. When the display goes south it usually burns the resistor for those segments.

#4 6 years ago

I've had this board out and looked at it closely when replacing the resisters. No lifted or otherwise compromised traces.

The problem is on the display controller board, not on the individual glasses. I swapped the displays and Displays 3 & 4 work fine when they're plugged into Players 1 & 2 - conversely, display 1 & 2 have the problem when they're plugged into players 3 & 4.

I have an idea it's the next chip up the line - the 7180 high voltage controller. Earlier I mis-read the schematics and thought it was the next chip down the line, the 4543 "BCD to 7-Seg converter" but after re-examining the schematic, it looks like maybe it's the 7180. I hate to just keep "shotgunning" these chips so- maybe someone has some experience with this board?

I have a firepower that has two missing displays at 3 & 4, I suppose I could just swap the boards from the two and then you wouldn't see the problem on 3 & 4, but to me that's akin to Cutting out the Replay knocker on an EM game when it sticks on. Ignoring, and cutting out a problem coil/display/toy etc, is not the way I like to fix things. I get really pissed when I see other "technicians" have "fixed" games in this manner. Besides, I get such a rush when I fix one of these things - the harder it is to find the better I feel when it's fixed.

-Brian

#5 6 years ago

A lot of times I will replace a smoked resistor and then the 1/4 amp slow blow fuse starts blowing on the PS or the resistor starts to burn up immediately again.

WMS probably should have used 1/2w or 1w resistors, but what im getting at is the resistor burns open because the HV switching chip is blown.

#6 6 years ago
Quoted from barakandl:

A lot of times I will replace a smoked resistor and then the 1/4 amp slow blow fuse starts blowing on the PS or the resistor starts to burn up immediately again.
WMS probably should have used 1/2w or 1w resistors, but what im getting at is the resistor burns open because the HV switching chip is blown.

I did put higher values in as the documentation suggests. So! You are thinking the high voltage switching chip (7180) as well - Cool!

#7 6 years ago
Quoted from bdPinball:

I've had this board out and looked at it closely when replacing the resisters. No lifted or otherwise compromised traces.

If you are confident with the traces on the main display board, it could just be the "c" wire in the wiring harness giving you the trouble with a missing segment. Or even the pin in the harness. They break all the time on me.

#8 6 years ago

I'll be the first to admit I'm still learning to read schematics, wiring diagrams, and the like. I'd say I'd like to read a "Theory of Operation" of this board, but heh, I'm imagining it would read like gibberish to me. Does the game control players 1 & 2, and 3 & 4 from seperate harnesses or wires on that harness? Or- is it a switching kind of thing where it tells the controller, "Okay, I'm talking about player 1 now, this is the data." I would be inclined to believe it addresses all four displays individually, but again, as Seargent Schultz says, "I know nothing!"

-Brian

2 weeks later
#9 6 years ago

Well, this gets more interesting. I socketed, and replaced that 7180 driver but that didn't fix the problem.

I've replaced the following components, which makes me believe it's maybe on the mpu?

- display,
- wire to the display,
- master display board

And that C segment is still out! This is frustrating. I do have a spare system 6 mpu I can throw in there to see if I can make it work.

I guess it could be the connector from the mpu to the master display. I didn't think the MPU had that level of control over the segments, I somehow assumed that the Mpu would tell the master display, "show me an 8!" And the board would know what to do.

-Brian

-Brian

#10 6 years ago
Quoted from bdPinball:

Well, this gets more interesting. I socketed, and replaced that 7180 driver but that didn't fix the problem.
I've replaced the following components, which makes me believe it's maybe on the mpu?
- display,
- wire to the display,
- master display board
And that C segment is still out! This is frustrating. I do have a spare system 6 mpu I can throw in there to see if I can make it work.
I guess it could be the connector from the mpu to the master display. I didn't think the MPU had that level of control over the segments, I somehow assumed that the Mpu would tell the master display, "show me an 8!" And the board would know what to do.
-Brian
-Brian

The MPU sends out 8 bits of encoded data for segment decoder chips on the master display board. four bits is for three of the displays, other four bits is for the remaining two displays.

I would replace the segment decoder on the MDB associated with the non working displays. Logic probe can figure out if that segment decoder output for C is active.

A bad display could be bringing down the segment too effecting the other display on the same circuit.

#11 6 years ago

Since I swapped out the master display board doesn't that rule out any chips on the MDB?

Now, something you said does make some sense though, if one of the displays isn't 100%, it could screw up the other displays. I swapped around the displays. And replaced #3, but I didn't replace 1, 2, or 4.

Im not doubting you- you obviously have a better grasp of this than I do, I'm just trying to learn how to fix this problem. I can see why people just give up and go with a pinscore or one of those.

Thanks.

-Brian

#12 6 years ago

Take a good 100% working display and put it in a position that acts up. Only have the one display hooked up and try again

If you have a logic probe, you can stick it on C pin of the segment decoder (usually 4543) and watch for activity. Be careful. There is 200v rail to rail on that board. zap! Can only use logic probe on the 5v circuits. You can get a rough idea if the hv chips are working with a dmm on VDC set in the range as long as it resolves pretty fast. Again.. careful of HV.

To further complicate things. A bad display could be damaging the master display board burning out the C segment circuit as soon as it is connected...

#13 6 years ago

My Fellow Pin-Gents,

Well! It ended up being display #4. I unplugged that one, and everything started working fine. I replaced it with one from a donor machine, and now that machine is complete. The Laser Ball that is. The Firepower on the other hand, nees *3* displays and a backglass.

Anyway, thanks for the clues, and the help with this one. I'm learning a little bit every time!

-BDPlaying Laser Ball!!!

Promoted items from the Pinside Marketplace
$ 9.95
Eproms
Pinballrom
Eproms
$ 44.99
Cabinet - Shooter Rods
Pinball Shark
Shooter rods
$ 150.00
Displays
Digipinball Shop
Displays
$ 27.95
Eproms
Pinballrom
Eproms
From: $ 90.00
Tools
Pincoder Store
Tools
From: $ 9.00
Boards
KAHR.US Circuits
Boards
From: $ 1.00
Playfield - Other
Rocket City Pinball
Other
$ 12.50
Lighting - Led
RoyGBev Pinball
Led
From: $ 11.00
Playfields
Troxel Repair
Playfields
From: $ 1.25
Playfield - Other
Rocket City Pinball
Other

Reply

Wanna join the discussion? Please sign in to reply to this topic.

Hey there! Welcome to Pinside!

Donate to Pinside

Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!


This page was printed from https://pinside.com/pinball/forum/topic/williams-system-3-7-display-segment-c-is-gone-on-players-2-3 and we tried optimising it for printing. Some page elements may have been deliberately hidden.

Scan the QR code on the left to jump to the URL this document was printed from.