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Weak Flippers - what else can I check?
- Thread starter MarkS
- Start date
mplayfield
Site Supporter
I have diodes I can take one with me to Johns if yo want. What number is on it
You should have diode test function on your multimeter BUT you have to cut off one leg to test it, so it’s easier to just replace with a new diode. Test the old one. If it’s faulty ie conducts in reverse direction then that’s your problem, if not, you still have a problem elsewhere.
mplayfield
Site Supporter
Thanks , I have those so will bring with me tomorrow @MarkS
I can only read the last 3 digits which are 007 - thanks @mplayfield
I don't have a multimeter, guess I will be back on YouTube to learn how to use one
Any recommendations?
I don't have a multimeter, guess I will be back on YouTube to learn how to use one
Any recommendations?
mplayfield
Site Supporter
Just change it easiest wayI can only read the last 3 digits which are 007 - thanks @mplayfield
I don't have a multimeter, guess I will be back on YouTube to learn how to use one
Yes I will change it, I just figured it was worth doing the check mentioned above to prove that's the issue before I turn it back on and blow another fuse? (Bound to need one later for something else too)
Also, I'm confused re the whole diode thing now - I thought a diode only allowed current to pass in one direction, so if it's in back-to-front why doesn't it just "not work"? If it's back-to-front, and then broken, how does this blow the fuse?
Don’t feel stupid, we have all done it. Repeatedly.
Last time I replaced a flipper mech with new plunger and sleeve etc, I put the coil on back to front *even though* I had taken pictures to prevent exactly that. I forgot to account for the fact the coil was incorrectly aligned before I started work (the lugs end of the coil should ideally be away from the end stop where the max vibration happens) so when I put it back together correctly, my photo became inverted.
Anyway within milliseconds the 70V blew 2 transistors on the board. I can’t remember if I also blew the coil diode or not, but probably. Then I also gave myself an electric shock off the board, prodding with my finger to see if a connector was loose.
Flipper coils have three lugs, two windings - one for the flip and another for the ‘hold’. I had fried the ‘hold’ transistors so my flipper would now flip but instantly drop back.
Fuc_king pinball. We should collect stamps or something instead.
Last time I replaced a flipper mech with new plunger and sleeve etc, I put the coil on back to front *even though* I had taken pictures to prevent exactly that. I forgot to account for the fact the coil was incorrectly aligned before I started work (the lugs end of the coil should ideally be away from the end stop where the max vibration happens) so when I put it back together correctly, my photo became inverted.
Anyway within milliseconds the 70V blew 2 transistors on the board. I can’t remember if I also blew the coil diode or not, but probably. Then I also gave myself an electric shock off the board, prodding with my finger to see if a connector was loose.
Flipper coils have three lugs, two windings - one for the flip and another for the ‘hold’. I had fried the ‘hold’ transistors so my flipper would now flip but instantly drop back.
Fuc_king pinball. We should collect stamps or something instead.
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Indeed.
My other favourite cock up is removing the component from a board , do a lovely clean job of it , then realising it was the one beside it you should have done and you only have one spare to hand ….. asaaagh
I now triple check and mark the component / board with a sharpie to guard against distraction and general f***wittery
mplayfield
Site Supporter
If the diode is in the wrong way round it will short out your flipper voltage to ground. The diode is there to deal with a phenomenon called “back emf” - when you flip a flipper the electricity produces magnetism that moves the plunger. When the electricity is cut to the coil the magnetic field collapses and this produces electricity in the opposite direction of the direction to its original electricity supply. That spike of energy can destroy your electronic circuitry, so the diode is there to conduct it away by effectively shorting out the reverse circuit.Yes I will change it, I just figured it was worth doing the check mentioned above to prove that's the issue before I turn it back on and blow another fuse? (Bound to need one later for something else too)
Also, I'm confused re the whole diode thing now - I thought a diode only allowed current to pass in one direction, so if it's in back-to-front why doesn't it just "not work"? If it's back-to-front, and then broken, how does this blow the fuse?
So in normal flipper operation when power is applied, the diode does nothing because it can only conduct one way. Once the power is switched off, it conducts the back emf voltage away.
If you connected it up the wrong way round it will have conducted a relatively high voltage and high current when you pressed the flipper button. and may now be damaged such that it conducts in both directions.
Hope this makes sense.
Thanks so much for the explanation AlanJ, I think it makes sense... hadn't thought about what happened when the magnetic field collapses 
Thank goodness you aren't a surgeon then
My other favourite cock up is removing the component from a board , do a lovely clean job of it , then realising it was the one beside it you should have done and you only have one spare to hand ….. asaaagh
I now triple check and mark the component / board with a sharpie to guard against distraction and general f***wittery
Thank goodness you aren't a surgeon then
The effects can be unpredictable; a High Speed that I played as a punter partly crashed on making the ramp shot with the upper flipper. The displays and feature lamps blanked out, the switch matrix stopped responding, but the flippers themselves, the bumpers and slingshots still worked, along with the background music. Turning it off and re-booting it had it apparently okay again. That very machine was in disgrace at the workshop when I applied for work - a later repeat had seen a few coils lock on and burn out. The primary culprit was the broken open-circuit diode on that upper flipper. It wasn't a first-tier machine any more in 1989, but it served for a bit longer after being rehabilitated.
The marking on the diode on coils was an indication of which was the live terminal, if I was intending to check a solenoid by jumpering it to ground. The later system 11 games no longer had diodes on all the coils; they were still used, but some were on the new-fangled 'Aux Power' board instead.
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