Big Game
Stern Electronics, 1980Hey Everyone, I finally got my Stern Big Game up and running (thanks to some help from you guys) but now I have display ghosting. The ghosting goes away once i unplug the player 4 display. Ive re-flowed all solder on the displays, and replaced the 1K ohm resistors. Is this normally caused by a bad IC on the display itself ? Thanks ! Click below for a video
Interesting issue.
Is it a specific display that causes the issue or will any display in the 4th player spot cause the issue.
Basic theory of operation is that every display gets the same information from the computer. They all use the same bcd segment data and digit enable. The only thing different is there is a unique "latch strobe" signal that tells a specific display to read the data. If ghosting is going on. The latche strobes could be considered out of timing.
Move the offending display to a different position and see what happens.
i've had this happen as well, turned out to be bad pins on the display plugs. Redid them all and problem solved. Inspect them closely. Mine were crumbling, corroded and crap.
I tried swapping the displays around, and as long as the "bad" display is connected, no matter what position its in it will cause the others to ghost. CaptainNeo, ive went through all the displays and re-soldered all the header pins and cleaned them up with a red scotchbrite. Also checked my HV section and its set at 170V.
How handy are you with a desoldering? What kind of diag tools do you have? Can you monitor the latch strobes, bcd segment data, and digit enable for oddities when that display is connected?
Depending on your setup i would recommend replacing the segment decoder. It is a 25 cent common component. 4543 i think is the part number. Seems like an unlikely cause, but ruling out other things i would go for that. Perhaps the decoder is not updating fast enough and some how leaving input lines in the wrong state for too long and it shows up on other displays??? Hrmmm
My pins were good on the boards, it was the pins in the plug that were shit. But if it moves with the display and fine, without one display in there, then you know that one is producing to much draw.
I am very good at desoldering and can get another 4543 in there no problem. As far as monitoring latch strobes and such, I dont have a logic probe or scope so think that is a bit out of my realm. Will try a new decoder IC and report back.
Problem is solved, and the problem was right in front of us all. Take a look at the video again guys, I cant believe I didnt spot it earlier ! Will post the fix if no one catches it soon. Think simple here, its nothing complex.
^^^^Winner ! I never spotted the 6 digit in there. I was sitting there just watching it count up 1,2,4,5,6,7....When one of the displays stopped at 6 I knew that was likely the problem. Swapped the 6 digit to ball/match and she works perfect now !! SWEET. Saved me the 65 mile round trip to get that 4543 IC.
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Dunmore, PA