In my 1981 Bally Embryon I have a display with extra segments for certain numbers, and another display with many missing digits.

1. I've swapped player 3 and 4 boards with player 1 and 2 connectors, where they then exhibit the same symptoms. To me, this eliminates the Player 3 and 4 connectors as possible cause.

2. I've reflowed the header pins on each board (to display and connector). No changes.

3. I'm reading Clays guides, and I see to check R1,3,4,5,7,9,11, and I get readings of 96-99 on each resistor while on the board. Seems correct? http://techniek.flipperwinkel.nl/ballyss/rep/index3.htm#display

Wondering for next steps to diagnose?

Any links or suggestions welcome.

thanks!
-mof

(oops please move to tech: solid state)

Ok, just checking all resistors, and found that on one board, r18 and r36 are 150ohms when expecting .3

Still checking...

-mof

Reviewing this now...
http://stevekulpa.net/pinball/bally_disp6r.htm

-mof

I noticed the two working displays (I presume) are Ballys.
The two failing displays are Stern.
I noticed that they look quite different from the back side.
Is that 'corrosion' on the leads that go down and solder to the pins on the Stern display?
-mof
stern
201404-EMB-back-of-stern.jpg
bally
201404-EMB-back-of-bally.jpg

I took another look at the two pics above. Should I be concerned that the Stern display appears to have corruption where the display meets the board? If so, how is this remedied?

-mof

Thanks, I'm looking at the two pics above in this thread. The first of the two is the Stern with missing digits.

-mof

barakandl I did some repairs on a 7-digit Bally display today.

Problem: 1,000 and 100,000 are out
Fix: Replace dead 100k resistors x 2: Fix worked

New problem. Missing TOP segment on all
Fix: replace Q13: Fix worked

New problem. TOP segment on all 7 digits is always-on
Fix: ???

Oops!

I installed the wrong transistor... Well back to square 2. New transistor did not fix the missing top segment on all displays

-mof

Bad decoder chip!

All fixed now!

-mof