First, make sure that each of the trough optos are indicating a ball is in the trough.
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Chris Hbler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

I have this trough opto problemon my IJ.
Few months ago it was the LED7. I replaced it and it wordek w/o problems since.
Now I have a weird one..
All optos are working. Tried them in the test mode.
They are all cleaned. I brushed the metal where the ball slides.
I basically did everything instructed here http://www.pinballrebel.com/game/pins/ij2/shop/Trough.htm
And I can easly play 10-20 balls without issues and then suddenly I get the End of play Bonus and keeping the ball on the playfield I'm on my next ball.
Really annoying if you play in multiplayer.
The machine is almost unusable because of this bug.

I tried to bend the PCB where the optos are and I can't get any glitches.
I can't replicate it. All the optos are fine and positioned well. Checked with my camera. They are all lit.
I'm running out of options here.
Anyone with the same issue?

Tried again today and got a new clue... it olny happens when 1 ball is locked!

Thought that maybe pinball wasn't leveled. Measured 7.2 degrees in the middle of the playfield. Adjusted the legs to get 6.5 so the balls will slide better on the trough.
Actually played fine for about 10 games (30 balls).
Thought for a second this might be it... and then bang.. Same thing. Ends the ball while you are still playing.

Did anyone experienced the same issue?

I took some time today for this issue again and focused on broken solder on resistor pins.
The problem was already narrowed down to Trough 5 opto switch (LED 6 and R6 on the board) so I checked the pins there.
Couldn't see it with my eye so I took a photo with my camera and zoomed it...
And here it was. Micro crack on R6.

20150730_153148.jpg

20150730_210623.jpg

Reflowed all 7 resistor pins, just to make sure there are no micro cracks anywhere else too and it's working fine now.