DE Solid State Flipper Issue - Locked On

[Calimori]

Last Friday I popped over to play CoolDan's latest collection of titles. Of his five set up machines, I had only played his AFM before and though I had played the other titles at some point, it as good to get some prolonged game play on them. However, him inviting me around was all just a trick to get me to fix his LW3 that had two faults. A dodgy DMD image and a locked on left flipper.
The DMD was tested in another machine and then the cables reseated the correct way to fit it. But the locked on left flipper was my first experience of working on a DE Solid State Flipper board.

Symptoms
The machine powers on and the flipper is not locked on immediately.
It stays locked on once the flipper has been activated.
It drops when the power is turned off

This sounded like the low power hold transistor (for left circuit) was maybe toasted but testing it shows it is fine. (TIP32c - Resistance: Red to centre leg, black to outer legs)
The TIP36C for high power flip also seem to be fine.
Diodes all give the same readings.

Any suggestions of what to try next as the pinrepair manuals I have do no have an electrical reason for lock on?

 

[pinballmania]

Can happen when the coil diode falls off. The drive circuit relies on this diode to collapse the current and allow the transistor to turn off.

 

[Calimori]

Thanks Andy, I will get Dan to check that as the machine is at his house.

 

[cooldan]

hey!

i didn't invite you over to fix, you bugger, i invited you to play. you totally mastered W?D with your megascore, you gotta admit it was pretty fun, especially when we ignored everything but the roulette wheel.

anyway. i'm reading this from a cheap hotel room in The Netherlands after a day at my dull job here. you forgot to mention that we decided it must be the driver or the predriver transistors so we took off that little board attached to the cabinet inside side wall after talking to GrizZ for help, but we couldn't figure out which components were good and which weren't.

so i can't test that diode right now, but will when i get home. and ...... er .... what about those transistors and other crap on that board thingy?

look at how handsome my son is:

 

[Calimori]

As per my first post, all the transistors are registering fine (TIP32 and TIP36) so the board appears not to be the issue.

All this has taught me for the second time running that I can't understand other peoples multimeters. I prefer my own and get the readings I was expecting rather than feeling a bit confused.
From now on, even if I am going rounds someones just to play pinball, I will be taking my multimeter as we will end up fixing something.

Whodunnit was mental, once I worked out the roulette shot, it was a buzz to gamble it all on black. It was however giving extra balls away like there was no tomorrow.

 

[cooldan]

Everyone loves an extra ball

 

[Spandangler]

Make sure you bring ya multi meter when you come to mine then Geoff! Ha ha ;-)

 

[Calimori]

Dan has replaced the coil diode and confirmed that the flipper now works properly and doesn't lock on. Thanks to Andy at Pinballmania for quickly offering the right solution, your help to this community is fantastic.