I've had a flickering display problem on another System 6, Blackout, but I never really got far with it and ended up selling it with the problem still present.

https://pinside.com/pinball/forum/topic/blackout-flickering-display

So now I have a Firepower with the same problem. The master display flickers constantly, moreso the fewer digits present. The main offender is the second from the right digit, but they all kind of suffer. I removed the 100v fuse and tested the input pins on IC4 (a UDN6184) which drives those digits. Without being able to read the exact ones and zeroes, the pulsing activity seems OK to me.

So now I want to test the output pins, but the fact that the 6184 is driven by 100 volts kind of scares me. The copies of Clay's guide that are floating around say that these chips are easily replaceable with a 6118, but that's not really true anymore, so I either have to work with what I have or find some kind of replacement.

Is there a safe way to test the output of the 6184 on this board? What should I look for when testing it?

All the stuff I've seen about display troubleshooting says to make sure the 100v is disabled before working on it. Isn't there a risk of shock if I do this?

I did a bunch of comparing IC13 (which drives player 3 and 4) to IC4 (which drives the master display). I know the readings on my meter won't be fully accurate (since I'm dealing with pulsing signals) but while all the input voltages are consistent across both chips, the output voltages differ widely. IC13's output voltages read right around 18 volts whereas IC4's outputs read around 10 or 11. The input voltages for the chips themselves is a stable 77 volts, so there's no difference there.

Is it safe to assume that the pulsing nature of these output signals means the variance is probably much greater than a simple 7 volts? If so, could that be what's causing the master display to flicker so much?

If I wanted to test this out, could I jump a used input pin to an un-used inpput, do the same for the output, and see what happens? Or do I need to clip the chip's legs first in order to try that?

I changed the diode on the power supply to drop the voltage from 100 to 90, and I wasn't sure if this voltage is regulated or not (assuming I'm using that word correctly) so I've been operating under the assumption that 77 volts might be OK. The four slave displays work fine at that voltage, but maybe the master display has more stringent requirements, despite all of them being driven by the same type of 6184 chip.

If anyone reading this has a System 6 close by, can you test pin 10 on IC4 and IC13 to see what voltage they're at?

I haven't gotten that working yet, but I have replacement coils on the way. The left one has part of the plastic tab that holds the lugs broken off and kind of floating. I may as well replace both and see what happens.

So for this display, bear in mind that I've done the voltage reduction on the power supply, so the 100v readings should be closer to 90v. That said, the input voltage on ZR1 is a crisp 89 volts, and the output side drops to 75 volts. That seems like a problem, no? Are diodes (even Zener ones) supposed to drop voltage that much?

Well, they're only 66 cents at the store nearby, so I'll replace it and see what happens. If it works, great. If not, then I tried. It's possible the display is just busted.

If replacing the Zener increases the voltage going into the 6184s, and that causes the master display to perform better, I may revert the 90v change on the power supply go to back to 100v and just accept that the display is on its last legs. It depends on what the owner wants to do.

No luck. The input voltage is around 90 volts, and the output voltage is around 80, but the displays haven't changed notably. There's still quite a bit of flicker on the second-from-right digit - moreso the fewer segments are lit. I thin kthis display is just on its last legs. I don't see any indication that putting the HV section of the power supply will have any effect.

Thanks for your help, eveyone. I think this is just a display on its way to the big backbox in the sky.

No luck.

I now have another used master display board in my possession, but the glass itself has a broken nipple, so it's useless. I also now have a spare slave display. Is it possible to use the glass from a slave display in the master board? Or are they not able to be mixed like that?

I never figured out what the problem was, but I put in an XPin LED set. It looks great!

Displays.JPG