Iron Maiden
Stern Electronics, 1982So I have a unique issue with a Early SS Stern 200 boardset. The displays only show 2's, 3's 6's and 7's. When I run display test mode. It goes 2, 3, 2, 3, 6, 7, 6, 7. and blanks. I reseated all the connections. All 5 displays do the exact same thing. Reseated the stiff ribbons at the top of the display board. And all other connectors. Nothing changed. I'm thinking a chip problem? Solved see post below.
I’m in the middle of a project, though I’m not at that point yet, but been reading a lot about the boards and such.
It’s definitely an IC if other simple things didn’t fix it. I believe one of the 4049 chips not sure exactly though.That number stuck in my head. There should be a few threads about strange number issues on the display. It’s usually all evens or all odds most of the time.
I think the 1's and 0's are blanks. because the displays sometimes show nothing in certain digits. so I think 2, and 3 are correct. 4 and 5 are 2 and 3. 6, 7 are correct. 8, and 9 are 6 and 7.
There are four BCD signals from the MPU board to the displays. These signals BCD0 thru BCD3 come from connector MPU J1-25 thru J1-28 respectively. Combinations of these four signals represent the various numbers to display. Can you see your problem?
'0' below represents logic low (0 volts).
'1' below represents logic high (5 volts).
Hmm so if BCD 1 was stuck high, from the top of the chart you'd get 2-3-2-3-6-7-6-7 and then two blanks for 8 and 9, right?
nice. So it being stuck high, means a bridged connection somewhere? either on chip or pins? or chip is bad?
so it's 8 and 9 that's blank, and 0 and 1, are actually showing 2 and 3. if i'm deciphering this correctly.
Quoted from CaptainNeo:so it's 8 and 9 that's blank, and 0 and 1, are actually showing 2 and 3. if i'm deciphering this correctly.
Right
Solved. It was indeed one of those pins not making contact. Repinned all 4 and now the displays all show correct digits.
So J1 of the mpu board. Last 4 pins at the bottom. Pins 22. 23 . 24 and 25.
Thanks everyone for the help and hopefully ill remember those 4 wires in the future.
20220809_214351 (resized).jpgThis thread came in handy, was working on my Lightning tonight and the playfield bonus display started doing horrible slow strobing and wrong digits showing up, a real mess. Did it once in a blue moon before but now it was stuck. Tried reflowing the headers on the little 'bonus board' and the female connector pins on both ends looked solid, tried another 6-digit display, still screwed up. So I tried that MPU connector up there, just reseated it a smidge and no more problem, so I'll have to repin that connector too.
Wanna join the discussion? Please sign in to reply to this topic.
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/stern-200-boardset-only-showing-236-s-and-7-s-on-the-displays 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.
Burlington, WI
