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IJ4 switch matrix query

paddythegreek

paddythegreek

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10 Years
Joined
Aug 30, 2011
Messages
2,062
Location
Leicester
Thought i had a couple of switches playing up but it turns out every drive sw with a green/yellow wire is inop. Checked at the plug on the cpu/snd board and on 3 of the working drive wires i have 3.25v and on the row that don't work it reads 2.55v. This is the same voltage with the plug connected or removed. Could it be the 3904 drive transistor. Thanks Ken
 
Update: the 3904 transistor was faulty. I replaced it and for a couple of balls everything worked fine.Its now taken out the transistor again. Help please.
 
i would have a good luck at all the switches in that row and check all the diodes
or repair that board again and try it in another game see if the same happens at least then you know if its a board fault or on the playfield
 
I've actually done this today.Ok not replaced the 3904 yet as the only stern i have is this IJ4,but i've checked the resistance between every sw in the faulty row and the cpu/snd board plug at J1. All read the same as a good working row. Took me ages but checked every soddin diode and found nothing. The sm 1K resistors in the sw circuit both read about 1k. Wondering if its the U1 chip .
 
Been in touch with chas siddiqi at stern technical who's given me several things to check out tomorrow.
 
Does this line go to the ark and crusade motors sw ,ie up sw and down sw .
If so you could disable in settings or unplug motors and them run game ?
:hmm:
 
Yea theyre both on the faulty line. Was gonna try that today but tbh it was bloody cold in the garage and got dragged christmas shopping so i thought it best to comply.I'll get my own back tomorrow. I'll put sugar in her early morning cuppa then lock myself in the bog.
 
Latest 8.10pm Tues.
One of the things Stern tech suggested was to check around the magnet area in case it was shorting to the bracket of the 3 stand up targets to the left of the magnet. It tuns out the magnet although it has a protective wrapper around the coil was right against the target bracket. The magnet wasn't a tight fit so it had turned enough (as the cable would allow) to rest against the bracket.I removed said magnet and rotated it 180 degrees. Problem solved.
I've played around 20 games and everythings working fine. Thanks to all who replied. Ken
 
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