Help/Advice for flipper driver transistor failing

[JWG9999]

Any help or advice please:

A flipper failed on my WPT. I tried replacing the coil but that didn't help.

The transistor had blown. Friends helped me to replace the transistor (I'm not great with a soldering iron) and the problem was fixed - but only for a while.

Mid-game the flipper started flapping up and down. I reached for the power switch but by then the transistor had blown again.

Am I looking for a short in the wiring or what?

 

[keith b smith]

Hi not that familiar with these boards but remember reading that some "sam " games had a problem with the mossfet overheating ? You need to google it but from memory they replaced the 22NE10l mossy with a more heavier duty moss number IRL540N, other than that maybe a faulty flipper control board (ie the small board on the back of the flipper button) but more than likely the other because you say its worked for a while after changing

 

[Fantazia2]

Is the EOS switch adjusted correctly and is the MPU seeing it being activated?

 

[JWG9999]

Is the EOS switch adjusted correctly and is the MPU seeing it being activated?

Thanks and yes, the EOS is ok - I don't know if the MPU is seeing it though.

 

[Moonraker]

You need to replace both the coil and transistor at the same time, otherwise one blows the other.

In the case above it sounds like the flipper coil is shorting once it has warmed up taking out the transistor.

EOS can be tested using the switch test and manually operating the flipper, if in doubt test the other flipper first, as you know that is good.

 

[mplayfield]

Wow that’s super interesting Peter, so will he have to remove the coil and somehow discharge it ?

 

[Moonraker]

Wow that’s super interesting Peter, so will he have to remove the coil and somehow discharge it ?

You're mixing coils with capacitors. You discharge capacitors. Coils effectively become magnets when power is applied. No power, no magnetism. When a coil is overheated because the transistor locked on, it can burn through the protective sheath of the wound wire. This can then either melt wire together creating an obvious short or it can cool down and work normally until it is heated up and shorts again as there's no protection remaining on the wound wire.

 

[Moonraker]

Also helps to clean flipper optos as dirty ones can cause flippers to lock on.

 

[mplayfield]

You're mixing coils with capacitors. You discharge capacitors. Coils effectively become magnets when power is applied. No power, no magnetism. When a coil is overheated because the transistor locked on, it can burn through the protective sheath of the wound wire. This can then either melt wire together creating an obvious short or it can cool down and work normally until it is heated up and shorts again as there's no protection remaining on the wound wire.

Thanks I think I understand .is this a rule of thumb on all games if a transistor goes and takes a coil with it?

 

[AlanJ]

Thanks I think I understand .is this a rule of thumb on all games if a transistor goes and takes a coil with it?

Yes, it's not always the coil but it's always worth checking. I measure the coils resistance and also look at it to see if it's "toasty".