Guns and roses magnets.. Help please

[The seeker]

hi I'm currently sorting out s friends pin gnr, it's been out of action for a while but I think I've got most of the minor faults sorted except the multi ball magnets, since I've never played one with working magnets it's tough to notice there missing but we're trying to fix her up and would live it if anyone could tell me if it's possible to buy new magnet boards for it or is it best to try to fix the fault ... Whatever it is ? I've not even started to fix this area of the game so I was wondering where the best place to start is ? Many thanks

 

[chris b]

I think somebody does the boards for them but should be a simple repair

 

[Dr. Pinball]

Fix the board, G n' R is a bit odd in the way that the under playfield magnet board is driven by low voltage long run wiring which unfortunately is really prone to interference. That translates to the magnets lock on until the FET driver transistors burn out. In fact they were so prone to issues on my G n' R before I added this fix simply running the playfield laser kickback test would lock on all three magnets....

So as heat and vibration caused issues on that board too I'd suggest that you change the three FET transistors which from memory are something like P20N10's. As they are hard to get so I usually put in IRL540's which are cheap. Secondly you need to stop future interference by suppressing the interference to the signals going into the 74HCT273 on the board. You need to solder a capacitor of around 0.27uF in parallel with resistors R6-R10, any non polarised variety should do, just piggyback them across the resistors by using the pads under the board. Here's the schematic and layout for the board to help as these are not usually in the manual:

Shout if you get stuck.