(Topic ID: 243864)

Black Knight display issue


By kevinclark

3 months ago



Topic Stats

  • 21 posts
  • 6 Pinsiders participating
  • Latest reply 7 days ago by kevinclark
  • Topic is favorited by 1 Pinsider

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s11disp21 (resized).jpg

#1 3 months ago

Hi folks - I’m fixing up a Black Knight that I grew up with (my mother got it for her birthday 30 years ago). This is my first repair, so while I’ve done a lot of reading in the last 72 hours, I’m not entirely sure what I’m looking at.

The machine has a number of issues, but most pressing is that the display is flakey because it’s keeping me from reading the switch test results. When I turn on the digits display, some numbers show up great and others are missing. If I let that number sit for a while, it will often show up. Examples here:


I swapped the player two and three cables and the problem moved from player two to player three. I reseated the cables on the display board, but no change. I haven’t changed the connections on the cpu board. When I tried to swap the credit/match cable with another display to see if it moved, neither worked (and I realized it was a 4 digit not a 7 digit display, so probably expected).

It sounds like a connection issue since the problem moves (at least on the player displays) but is it possible this is out gassing? I don’t have a solid understanding of what that looks like.

Thanks!

#2 3 months ago

Display could be out gassing, cold solder joints on display board and on mpu board for tbe displays .

#3 3 months ago

How does one diagnose off gassing? Is it just through a process of elimination? I.e, if the connections check out that’s what it is?

#4 3 months ago

If the display is partial, or spotty.

#5 3 months ago
s11disp21 (resized).jpg
#6 3 months ago

Got it. And the fix for offgassing is new displays?

#7 3 months ago

Yes it is. You could look for a used one or go with an led set and you would eliminate all the old displays and its display driver board.

#8 3 months ago

I had a WMS sys 7 (like black knight) that had similar issues (the scrolling/fading). If I recall though, I was not missing any digits - just slowing scrolling/fading such that not you couldn't read the entire score at once.

This fix per the "pinrepair" guides worked for me:
Fading/Scrolling Score Displays.
If the score displays on a System3 to System7 game slowly fade in a scrolling fashion, check the high voltage C1/C3 (100 mfd 150 volt) filter capacitors on the power supply board.

#9 3 months ago
Quoted from jeffc:

This fix per the "pinrepair" guides worked for me:
Fading/Scrolling Score Displays.
If the score displays on a System3 to System7 game slowly fade in a scrolling fashion, check the high voltage C1/C3 (100 mfd 150 volt) filter capacitors on the power supply board.

Good call. I see in the schematics that the C1 cap is associated with the 1/2/Match segment decoders and get why that might be the underlying issue (especially since its those three displays that have issues). but I don’t see C3 and the bill of goods indicates there isn’t one afaict. C2 drives 2/4/Credit though, so maybe that’s what the guide meant?

jeffc Mind linking to it? I didn’t see a Williams guide on pinrepair.

#10 3 months ago

I’m also seeing “.01 MFD. 50 V.”, so maybe I’m looking at the wrong thing?

#11 3 months ago

The C1/C3 refers to the caps on the power supply board, not display board.

#12 3 months ago

jeffc Ah! Got it, thank you!

#13 3 months ago

Looks like a great time to replace all your electrolytic capacitors on the power supply. Here is a list of them that includes the C1/C3. https://www.greatplainselectronics.com/proddetail.asp?prod=W711A-PEC-KIT

#14 3 months ago

What are you going to do with the machine? Keep it? If so I recommend just buying a rottendog led display set and be done. Even if you repair it, won't be long and another issue will pop up.

#15 3 months ago
Quoted from PinballManiac40:

Looks like a great time to replace all your electrolytic capacitors on the power supply. Here is a list of them that includes the C1/C3. https://www.greatplainselectronics.com/proddetail.asp?prod=W711A-PEC-KIT

Ed at GPE is a great guy & asset for the hobby. His "kit" is listed as out of stock, but you can still (most likely) order the parts individually from him.

#16 3 months ago
Quoted from Travish:

What are you going to do with the machine? Keep it? If so I recommend just buying a rottendog led display set and be done. Even if you repair it, won't be long and another issue will pop up.

From what I’m hearing it sounds like this isn’t off gassing. If it were, it’d be pretty convenient that it’s just related displays (1/2/match) and it wouldn’t make sense that the behavior moves when I swap displays.

I’m going to keep the machine long term, but it’s had pretty limited home use so I’m not worried about all my displays failing soon if I’m not seeing off gassing yet. If the HV rework doesn’t solve it I’ll consider it though.

#17 3 months ago

When you said you swapped cables, did you mean you moved the cable from P2 display and P2 position on the disply board to P3 display and P3 display board? If so, that points to a flakey ribbon cable and you should either replace them (best long term solution) or attempt to clean the ribbon cable connectors using contact cleaner like DeOxit.

#18 3 months ago
Quoted from Schwaggs:

When you said you swapped cables, did you mean you moved the cable from P2 display and P2 position on the disply board to P3 display and P3 display board? If so, that points to a flakey ribbon cable and you should either replace them (best long term solution) or attempt to clean the ribbon cable connectors using contact cleaner like DeOxit.

I took the cable that was attached to the P2 source on the display board, detached it from the P2 glass, and attached it to the P3 glass. Then I connected the P3 source to the P2 glass. The behavior swapped. So, could still be the cable. But it could be the source too. I haven’t tried swapping cables entirely yet.

#19 3 months ago
Quoted from kevinclark:

I took the cable that was attached to the P2 source on the display board, detached it from the P2 glass, and attached it to the P3 glass. Then I connected the P3 source to the P2 glass. The behavior swapped. So, could still be the cable. But it could be the source too. I haven’t tried swapping cables entirely yet.

Ah, that is a little less clear solution. Try swapping both ends of the cable (the entire cable moves from P2 to P3 and vice-versa).

If the problem moves with the entire cable moved, it is not likely the glass.

Next I would try reseating the large card-edge connector on the master display board and retest to see if anything changes (some digits start to display).

Then I would try reseating the connectors across the top of the CPU board and retest.

DO NOT work on the displays and cables with the power on. These things work on very high voltage that can hurt you.

#20 3 months ago
Quoted from Schwaggs:

DO NOT work on the displays and cables with the power on. These things work on very high voltage that can hurt you.

or damage the display board

3 months later
#21 7 days ago

Just to follow up, I replaced the caps on the power board (and replaced the other components in the power section of Vid’s bulletproofing guide) and the digits look way better. When it first turns on the 3s, 7s, and middle segment of the 8s are still flakey, but once it warms up they show up fine. I’m no longer getting any faded digits.

Thanks a lot!

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