Author Topic: Firepower 2 circuit board issues  (Read 1299 times)

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Offline FirePower

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Re: 2N4401 transistors Firepower 2
« on: November 29, 2009, 11:36:28 AM »
Hi Rob,

Good to see someone taking on a basket case electronic board. I've never had any success in using the in circuit transistor measurement techniques described in the Pinrepair guide, but they are tremendous guides.

I've had some problems in this solenoid drive area on a WMS driver board, mine was a sys 6 game, but I think the FP2 uses the same board. In general comments I'd rate the chance of a 2N4401 being blown as pretty low, they are driven by logic level chips and drive the final TIP102. Much more likely to be the TIP102 blown, particularly if you have locked on solenoids. I'd be checking solenoid resistance and diode quality. (I suppose if someone has totally butchered it by soldering the inter board connector and other pieces of genius, it is possible that somehow the logic supply voltage is incorrectly connected and this could do all pre-drive transistors, but I would expect many more problem than just 2N4401s - out of interest have you run a meter over the power supply board?  I'd do this very early.)  Also do you know of the other WMS guides around www.pinball.flippers.info present an alternate view which may be beneficial.

On the resistors I wouldn't be too concerned about the seemingly out of spec measurements. From memory they are just pull ups / pull downs or used as current limiters for the C-E path.  If they were either open circuit or short circuit I'd be concerned, but yours are about right and for the range of other problems you seem to have I would not be fretting on them just yet.

For my problems I found it really beneficial to use a logic probe and examine the driving side logic and behaviour. With a jumper wire and power to the board (but not the solenoids - lift the solenoid fuse and maybe the connectors) you can step through and simulate every kind of driven condition, by this I mean special solenoid drive, solenoid test drive, drive from cpu and game over lock out. This gave me much clearer understanding of what was happening in the circuit. I sketched out a single leg of the drive for one solenoid and noted logic conditions and voltage etc. This dog eared piece of paper is in a log book and I'm happy to scan and flick it you way if you feel it may be of any use.