BK2K Kickback Coil.

[DanLewell]

so my BK2K developed a fault while we were at the Welsh pinball weekend.

Kept blowing one of the fuses, which meant the drops wouldn't reset, vuk wouldn't work, it wouldn't kick out locked balls.

Fortunately for me, poibug was on hand with his circuit breakers, which helped in the troubleshooting.

Turns out it was the kickback coil, it would lock on as soon as it was switched on, killing the fuse.

We tested the transistor and could see it was knackered. So replaced that and it looked to be ok again, everything was working... until the kickback got used in a game and then it killed the transistor again, coil locked on, which in turn killed the fuse again.

It was quite late in the day so we gave up on it there and I brought it back home.

First thing I needed to do was create some circuit breakers, so much easier than changing the fuse every two minutes. Bits arrived yesterday so I made them up this morning and got back into it.

Powered up and same thing is happening. Kick back coil locks on until the circuit breaker trips. I was expecting this because I haven't fixed the board again yet. So, board out, change the tip102, didn't change the pre driver transistor because it's testing consistently with all the others that are there (and I don't have any because I screwed the order up in the week and they're not getting here until Monday. ) Also fitted a remote battery holder and got rid of the chewing gum wrapper hack so I don't get shot by @TYHO when I take this up to nlp in October

But because I don't want to knacker the tip102 again, I thought I should have a look at the coil before connecting it up. Desoldered it and measured resistance and I'm getting about 4 ohms. Now, I don't know if that's right or not but BK2K uses the same coil for the trough kicker so desoldered that and checked resistance and it's about the same, so the coil looks ok.

Reconnected the trough kicker, but left the kickback un-connected for now. Powered up and everything is working fine (except the kick back obviously).

Tip102 is testing ok on the board still, despite the kickback switch registering. So it doesn't look like anything on the board is killing it, although I'm not sure it would do anything without the coil attached??

So, I'm a bit unsure of what to try next:

1. Connect it up and hope the pinball fairies have fixed it by me doing nothing?
2. Swap the coil for the trough kicker one to see if the fault moves with the coil or stays with the kickback?
3. Something else?

 

[pinballmania]

Replace the diode on the coil ? If missing or broken it will kill the transistor on the coils first use.

 

[DanLewell]

I went for option 2 and switched the two coils over.

And the problem has disappeared. So, no idea what caused it, which is a bit infuriating but at least it's working again.

I did think there should be diodes but neither of these coils has them?

Does bk2k have some wierd design feature with the diodes all together on a separate board or something?

 

[kevlar]

Have you traced the wiring back from the coil? I had something similar on my shadow a while back, a bare bit of wire was shorting on the cabinet speaker.

Edit.... Ignore that, I see you've sorted it.

 

[Spandangler]

The diodes are on the board I think

 

[Jonwolf]

I went for option 2 and switched the two coils over.

And the problem has disappeared. So, no idea what caused it, which is a bit infuriating but at least it's working again.

I did think there should be diodes but neither of these coils has them?

Does bk2k have some wierd design feature with the diodes all together on a separate board or something?

Swapping the coils over has fixed them - maybe one of them was shorting and the swap has solved it ?

I once had an issue on a TZ where the wire emerging from the coil was shorting on a metal bracket.

Anyway - glad it's sorted for you



Sent from my iPad using Tapatalk

 

[Poibug]

so my BK2K developed a fault while we were at the Welsh pinball weekend.

Kept blowing one of the fuses, which meant the drops wouldn't reset, vuk wouldn't work, it wouldn't kick out locked balls.

Fortunately for me, poibug was on hand with his circuit breakers, which helped in the troubleshooting.

Turns out it was the kickback coil, it would lock on as soon as it was switched on, killing the fuse.

We tested the transistor and could see it was knackered. So replaced that and it looked to be ok again, everything was working... until the kickback got used in a game and then it killed the transistor again, coil locked on, which in turn killed the fuse again.

It was quite late in the day so we gave up on it there and I brought it back home.

First thing I needed to do was create some circuit breakers, so much easier than changing the fuse every two minutes. Bits arrived yesterday so I made them up this morning and got back into it.

Powered up and same thing is happening. Kick back coil locks on until the circuit breaker trips. I was expecting this because I haven't fixed the board again yet. So, board out, change the tip102, didn't change the pre driver transistor because it's testing consistently with all the others that are there (and I don't have any because I screwed the order up in the week and they're not getting here until Monday. ) Also fitted a remote battery holder and got rid of the chewing gum wrapper hack so I don't get shot by @TYHO when I take this up to nlp in October

But because I don't want to knacker the tip102 again, I thought I should have a look at the coil before connecting it up. Desoldered it and measured resistance and I'm getting about 4 ohms. Now, I don't know if that's right or not but BK2K uses the same coil for the trough kicker so desoldered that and checked resistance and it's about the same, so the coil looks ok.

Reconnected the trough kicker, but left the kickback un-connected for now. Powered up and everything is working fine (except the kick back obviously).

Tip102 is testing ok on the board still, despite the kickback switch registering. So it doesn't look like anything on the board is killing it, although I'm not sure it would do anything without the coil attached??

So, I'm a bit unsure of what to try next:

1. Connect it up and hope the pinball fairies have fixed it by me doing nothing?
2. Swap the coil for the trough kicker one to see if the fault moves with the coil or stays with the kickback?
3. Something else?

Awwww,was looking forward to berating ya over the holder

 

[PinballDaze]

Had a faulty coil on a Fishtales top box flapper thing. Tested low, replaced. All working. Tested coil off machine (and I still don't know why?) but it was about 4 Ohms. Took off wrapper and it was evident that it had been getting hot and insulation was damaged. Binned

 

[Jay Walker]

I went for option 2 and switched the two coils over.

And the problem has disappeared. So, no idea what caused it, which is a bit infuriating but at least it's working again.

I did think there should be diodes but neither of these coils has them?

Does bk2k have some wierd design feature with the diodes all together on a separate board or something?

Yes, Dan,

The later system 11 games have the tie-back diodes placed on the 'Aux Driver' board, along with the 50v and 25v bridge rectifiers, solenoid extender relay, and its diode network.