embryon coil locked on

[pinball god]

installed a knocker assembly and tested ok. replaced a diode on a pop bumper and lane switch and reattached the caps I disconnected. had a game and was not happy with the pop operation and the lane switch came on by itself through vibration. Adjusted both mechs and went into solenoid test to see how the pop went. Third cycle, the pop fired twice instead of once and then during the test cycle I heard a large hum and quickly powered off. Figured maybe a coil is locked on, so powered quickly and the knocker coil fires and stays on.

So can someone refresh my memory of what component(s) could be stuffed to cause this. Also could a pcb be in trouble or have a switched off in time. I'm guessing time for some parts, but am unsure of what and what needs to be tested first. thanks

[Marty Machine]

With everything OFF, does the coil in question move FREELY with nothing rubbing or catching inside?

This will eliminate whether the coil itself is burnt & stuffed....then move onto control boards etc...

MM

[pinball god]

With everything OFF, does the coil in question move FREELY with nothing rubbing or catching inside?

This will eliminate whether the coil itself is burnt & stuffed....then move onto control boards etc...

MM

nice and free, repeated power ons will fire it and off it releases quickly. now whats next please

[pinball god]

pulled out solenoid pcb and transistor Q3 looked faulty out of .4-.6 range. Can someone confirm if its a tip101/tip102.

Also are there other components I should test before ordering transistors and finally what would cause it to blow? What should I check for if anything so I don't spend half my life replacing the transistor. Q3 is the knocker transistor of which I just installed an old knocker to the game.

[Retropin]

Is the knocker coil the right value? The current backwash of these can be quite large and its normally diode protected to prevent the backwash travelling up the signal path and through the associated transistor... 7XXX buffer chip and then the interface chip or 4XXX signal chip.
Sounds like you had a large current backwash. It MIGHT have stopped at the transistor but if it went further the buffer could be short etc which would possibly make the coil fire every time you turn the game on even if you replace the TIPXXX

[pinball god]

Is the knocker coil the right value? The current backwash of these can be quite large and its normally diode protected to prevent the backwash travelling up the signal path and through the associated transistor... 7XXX buffer chip and then the interface chip or 4XXX signal chip.
Sounds like you had a large current backwash. It MIGHT have stopped at the transistor but if it went further the buffer could be short etc which would possibly make the coil fire every time you turn the game on even if you replace the TIPXXX

check and ok 26-1200 as per manual specs. It does have a diode. Should I some how check this? thanks

[Strangeways]

TIP120 will do the job. You did solder the power (yellow wires from memory) to the banded side of the diode on the coil ?

I have the TIP120 handy if you need one 

[pinball god]

TIP120 will do the job. You did solder the power (yellow wires from memory) to the banded side of the diode on the coil ?

I have the TIP120 handy if you need one 

will order some tip120 from Greg but may grab one from you in the meantime and bring back when the order comes. BTW is tip120/122 the same and are they ok in place of tip101's.

I connected the two green wires to banded, tested coil and got 10.7ohms just like on the space invaders. Checked banding on the pop bumper and switch I replaced and ok. Can these just give out or does something cause it that I need to address?

Might see you tomorrow mate.

[pinball god]

Tip120 replaced on Q3 and no coil lock. Fired knocker twice and had a game with no dramas but didn't want to push my luck so close to bedtime. Will give the embryon a good going on sunday. Thanks Nino for the transistor, will fix you up when I get my order.