(Topic ID: 263661)

Stern Lightning, LED flicker only for certain controlled lamps??


By frenchmarky

10 months ago



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  • 5 posts
  • 3 Pinsiders participating
  • Latest reply 10 months ago by barakandl
  • Topic is favorited by 1 Pinsider

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#1 10 months ago

I installed a repro translite and prefer 44s, but I did put extra brite LEDs behind Tilt, Game Over, Match, Hi Score & Shoot Again because even 44s are much too dim for these spots compared to the original backglass, because they are hidden behind a dark color layer when not lit.
However the three across the top flicker when on, the other two bottom ones at left don’t. It’s not the LEDs because I have swapped all sorts/brands/styles/ghosting/non-ghosting/ages I have laying around here and still ONLY these three positions flicker and always do. And I mean flicker BAD like "yo dude, ain't no LED 'posed to be screwed in here!" bad. It’s not just power fluctuations from the game’s random attract mode because it does the same thing in the burn-in and lamp test mode (photo). If I put regular 44s in all five sockets, no visible flicker, same brightness. I don't get it, they're all controlled lamps, why not all flicker or all not? Any ideas?
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#2 10 months ago

Argh, after poking around in here some more, apparently I need to add 470 ohm resistors to these sockets. I tried one and it worked on that lamp. I had thought that a resistor was for keeping leds from lighting when they shouldn't (ghosting), instead of these which are cutting in and out when they should be solidly on. Fixed!

#3 10 months ago

Yes, the LED draws so little current that the driver SCR will not stay on, and some extra load is needed.

#4 10 months ago

Apparently the two leds that didn't flicker were just barely on the edge of locking their SCRs good because after reseating some connectors, they started the darn flickering too so I added resistors to all five.

#5 10 months ago
Quoted from frenchmarky:

Apparently the two leds that didn't flicker were just barely on the edge of locking their SCRs good because after reseating some connectors, they started the darn flickering too so I added resistors to all five.

Resistance in the bulb socket could limit current enough to push you over the edge of not latching and flickering. The CPU starts to turn on the feature lamps close to zero volts to preserve incandescent bulb life. The first lamps to be turned on are the most likely to flicker. The lamps updated last (higher decoder output numbers) are less likely to flicker.

Usually you can put the game in lamp test. In this state the load is highest so the voltage is lowest and if a led lamp is going to flicker, it will do so in lamp test. Then just resistor all the lamps that flicker during lamp test and you should be good to go.

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