I encountered this problem with the leds on the "Mode sign" panel and I assumed it was a transistor problem.
All of them are flickering during the game. The leds work as they should in the lamp test mode. However, when in the lamp test I check a different lamp that belongs to the same columm as the one in the mode sign the led in the mode sign is lit. I thought the problem could be the transistor Q42 that controls that row. I have tried my Mode sign in my friend's house who has got the same pinball and the leds are behaving the same way while his "mode sing" works flawlessly. So the problem with the transistor is discarded.
The first led is not working at all. This board only has leds and resistors. Something is wrong and I don't know what it is.

Any help is really appreciated.

I've already checked continuity from the pins on the header to the tracks and all of them work ok.

I've followed your piece of advice and heated up all the joints on the header. Unfortunately it hasn't solved the problem and the leds keep flickering.
Thank you for your help.

Behaviour on attract mode.

On the next video you can see that the leds behave as they should on test mode.

Thank you lyosden for your time. I was checking the leds with the multimeter. When I put the two probes on the legs of the first led it beeped. None of the other leds did that. Does it mean the first led is defective?

Here you are

IMG_20170728_153756 (resized).jpg

Thank you for the links. Even though I'm not in the u.s I'll take those references to get them.
I'll start changing the top beige resistor since the original triangle shaped led is difficult to get.

In case the led is defective. I was planning to cut the end part of the original one and glue it on top of the new led. This way I can keep the original appearance of the board.

I really appreciate your help

Problem solved.

I have checked all the resistors and all of them were ok. Then I checked the leds and all of them lit but the first one.
I have taken the first led out since it is clear now that it is the cause of all the problems. I have reassembled the board on the pinball and now all the leds are working as they should.
I missing one led, the first one. I'll look for one replacement.

Thanks again for your help.

Thank you for the link.
I have ordered order some leds in a electronic store near my city. They appear to be the same size and shape as the ones used in the pinball. I hope they work.

This is the led I have ordered.

(If = 10mA): 1.25 - 8mcd

diodo-led-5x7mm-verde-triangular-1-8600_thumb_450x450 (resized).png

Ref. L323GD

Thank you. That is an interesting tool to know which led will be good for our pinball.
According to the specifiations given in this link : https://www.soselectronic.com/products/kingbright/l-323-gd-12032
I think the led I have ordered is very similar to the one you have posted.

2017-08-03 (2) (resized).png

I think I will get them by Friday. I'll post the result.

I hace just received them. They are identical.
Standing side by side.

IMG_20170803_125003-1 (resized).jpg

Led installed and...

IMG_20170803_131721 (resized).jpg

... WORKING!!

Thank you for taking your time to help me lyonsden.

I posted it some posts above. The led number is L323GD.

More information in this link: https://www.soselectronic.com/products/kingbright/l-323-gd-12032