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Shadow arrived yesterday, tried to burn the house down today.

kevlar

kevlar

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10 Years
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Apr 11, 2013
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Newport, South Wales
My shadow arrived yesterday and all was working fine bar for a few niggles here and there. The balls were getting held up sometimes in the trough, not moving down after a ball had been ejected so I played around with it a little. Turning the machine back on I was greeted with the message " check fuses F114 & F115 but then it continued to its normal state after a few solenoid tests. While testing the trough by launching ball after ball and letting them drain I looked up and saw smoke coming from the battlefield. At first I thought " cool battlefield effect " then realised I was about to lose my house so pulled the plug quick. Lifting the battlefield revealed that the drop target bank coil was very hot and melting the coil sleeve. I tried pushing the coil plunger thinking something must have jammed it but it would no longer go inside the coil as the sleeve had melted and collapsed. The fuses mentioned earlier were found to be ok.

OK, new coil ordered but I'm trying to get to the bottom of why this happened. The transistor Q32 and diode seem to test ok with my limited knowledge by comparing to others on the board. Saying that I could do with knowing how to properly test the transistor so if anyone can tell me the proper way I'd be grateful.

At the time of burnout all the drop targets were actually up but when I first saw the coil it was extended which is its normal position after resetting the targets but I guess it could have dropped to that position.

I've gone on long enough for now, has anyone had a similar problem or have some pointers for me?

thanks

Kev
 
I've had issues with a drop target reset "coil off" switches coming loose after a pin has been moved and then not working correctly, taking the coil and drive transistor out in the process. Sounds like you've had something similar happen... I think you need to check how the coil is activated/de-activated for each of the battlefield drop targets.

To test the transistor select diode setting on the meter and measure the transistor legs. Compare with other transistors on the board to decide if ok or not.

Oh and I suspect the check F114 and F115 may be a seperate issue as that is not a normal message when you fry a coil... :suspicious:

Good luck.
 
Thanks moonraker, the only transistor setting I can see on my meter is not on the main dial but one of those little circles with a few small holes, I think you actually place small transistors onto it to test them. Correct me if I'm talking Boll***s.
 
kevlar said:
Thanks moonraker, the only transistor setting I can see on my meter is not on the main dial but one of those little circles with a few small holes, I think you actually place small transistors onto it to test them. Correct me if I'm talking Boll***s.
Click to expand...

You can verify a transistor is OK by checking resistance too...
 
So I was thinking, with the coil removed and cables cut, measuring the voltage across the 2 wires should show nothing if everything is well, correct? i.e. one side is live but the other side should go nowhere as the transistor hasn't switched? if this assumption is true then if you actually measure a voltage at this point then the transistor must be dead short? I'm actually measuring 90 odd volts so either my meter is way out, it is a cheap one! or something else is up.

Please correct me if I've got that wrong.
 
kevlar said:
if you actually measure a voltage at this point then the transistor must be dead short? Please correct me if I've got that wrong.
Click to expand...

Yep you're wrong (if I've understood you correctly) - the transistor normally provides the path to earth and when it operates it completes the circuit and the coil fires. Hence you can test fire coils by shorting the relevant lug to earth.
 
Thanks for the help moonraker. If the path to earth was made ( in the normal coil not firing mode ) wouldn't the coil fire as the current is flowing to earth?

I think we're just miss-understanding each other. The article confirmed to me what I was trying to say.
 
Wow !! this thread has just gone totally over my head,what did you guys just talk about :noidea: ;)
 
kevlar said:
So I was thinking, with the coil removed and cables cut, measuring the voltage across the 2 wires should show nothing if everything is well, correct? i.e. one side is live but the other side should go nowhere as the transistor hasn't switched? if this assumption is true then if you actually measure a voltage at this point then the transistor must be dead short? I'm actually measuring 90 odd volts so either my meter is way out, it is a cheap one! or something else is up.

Please correct me if I've got that wrong.
Click to expand...

Yes. You are right. The fact that you can measure volts between where the coil should be means that you have a transistor short ( or random short in the wiring perhaps). 90v is not an unusual reading. The nominal voltages in the schematics are 'under load'. When no load, the volt reading will be higher.
 
pinballmania said:
Yes. You are right. The fact that you can measure volts between where the coil should be means that you have a transistor short ( or random short in the wiring perhaps). 90v is not an unusual reading. The nominal voltages in the schematics are 'under load'. When no load, the volt reading will be higher.
Click to expand...

Thanks Andy, I'm glad someone understood my attempt to explain my problem which came out as gibberish! :loco:
 
Ok, I need the help of the brightest minds here. After determining that the transistor was short to earth I removed the board, tested again while it was out and it was definitely dead short to earth. I replaced the transistor ( Q32, tip102 ) and retested. Short gone and all pins soldered ok. Refitted the board and everything else was still working ( coil not arrived yet ). Fitted new coil today, tested transistor again, still ok. Powered up and coil energised immediately. Powered off, retested transistor, dead short to earth again. Tested continuity from coil to earth and of course it had continuity as the transistor is shorted so I unplugged connectors J107 and J126. First unplugging J107 and retesting from coil to earth, still shorted. Removed J126 and retested, short gone so in my mind the wiring is ok and the only short is the transistor. So why did the transistor go again? could it be the other small transistor 2N5401 that switches the tip102 is faulty and causing this? ( taken from http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Transistor_.22Quick_Check.22 )

The other thing that bothers me is since replacing the transistor I've been playing the pin with the coil removed ( so no drop targets ) and the transistor didn't blow, it only blew when playing with the coil connected. This makes me think the wiring is actually fault despite what I said above.

Help guys, I'm already bald so I've started pulling my eyebrows out.
 
Taken from the 'Bible':

If after replacing the driver transistors the coil/flashlamp is still stuck on, then replace the TTL 74LS374 logic chip. The TTL 74LS374 can also go bad (though it is not real common).
Also remember to test the resistance of a coil after replacing the driver transistors. If a coil gets hot, it can burn the painted enamel insulation off the coil windings. This lowers the overall resistance of the coil because adjacent windings short together. If resistance gets much below 3 ohms, the coil becomes a "short", and will fry its associated driver transistors very quickly!

If a coil locked on really hard and for a period of time (and without blowing the coil fuse, over fused?), the controlling 74LS374 chip may have also died. If after replacing the TIP driver transistor(s) and the smaller pre-driver transistor, the coil is still locked on, now is the time to replace the 74LS374 TTL chip. Use the schematics and trace the transistors in question back to the 74LS374 chip. This will be chip U2, U3, U4, or U5 on WPC-S and prior driver boards, or chip U4, U5, U6, or U7 on WPC-95 driver boards.

If everything has been tested from the TIP102 back to the coil itself. That only leaves the TIP102 itself, its pre-driver transistor, and the logic chip that controls the transistors. It has to be one (or more!) of these devices that are causing the problem.
 
Thanks for that info. If it was any of the other components on the board before the tip102 wouldn't it have shorted even before I connected the coil up? Like I said the Transistor remained healthy until I powered up with the new coil in circuit then it immediately shorted to earth.
 
kevlar said:
Thanks for that info. If it was any of the other components on the board before the tip102 wouldn't it have shorted even before I connected the coil up? .
Click to expand...

No because the circuit was incomplete (no coil) until you added the coil which made the circuit allowing it to short.

kevlar said:
Like I said the Transistor remained healthy until I powered up with the new coil in circuit then it immediately shorted to earth.
Click to expand...

It will... you need to replace the Transistor, the pre-drive transistor and most probably the relevant IC.
 
Yesterday I traced every inch of wire from the coil back to the board and found an exposed burnt section that must have been shorting on the speaker. It wasn't one of the main wires to the coil but one that branched off, connected to the single mini dropdown coil and then went back to the driver board, think its called a diode tieback loop or something like that in the manual. Anyway, repaired the damaged wire, replaced the tip102 and the pre-drive transistor just incase ( I have no idea if that was gone also ) and its working again.

Lessons learnt? don't just have a quick look at the wiring, physically trace it back inch by inch!.

Thanks to all for the help, especially Moonraker and Andy.
 
Had an interesting one today. All of a sudden I was getting random slam tilts and the first 3 or 4 times it happened was during multiball so I thought it might be a bug of the patched rom I installed. Swapping the rom back to the original one dispelled that theory. I started going through the switch edge test and everything looked ok except the MO(N)GOL switch also activated the right ramp entry opto which is in the same row. Further testing showed the right and left ramp entry optos were the wrong way around so swapped the plugs on the opto board. The fault was still there at this point. Then I remembered I had a wire come off the MO(N)GOL standup yesterday and I had soldered it back on...........guess what? the wrong side of the diode!. What a beginners mistake! ( well I do still have training wheels on despite owning a pin for over 6 months ). Re-soldered to the correct side of the diode and everything is working properly again. What a strange effect connecting to the wrong side of a diode! caused another switch in the same row to activate and caused slam tilts which isn't even in the same row/column!. The latter I have no idea how it was causing it but it hasn't happened since I moved the wire back.
 
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