(Topic ID: 265803)

NBA Fastbreak: High Powered Coils Locked on (J116) Help!


By MiamiRedSkin

52 days ago



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  • 14 posts
  • 6 Pinsiders participating
  • Latest reply 49 days ago by Ronkz650
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#1 52 days ago

Hi All -

I'm not the most electrical-inclined, and I'm experiencing quite a frustrating issue with my NBA Fastbreak. With social distancing in full effect, I feel this would be a great time for me to dive in and try to learn!

I picked up this NBA Fastbreak not working, so it's not acting up because of an issue or mistake that I have made. Upon start up, I noticed that F103 kept on blowing. I started to disconnect some of the coils feeding that fuse, and it seems most of my high power coils are locking on. Upon disconnecting one coil, the next coil starts to lock on. Now, the fuse will not blow, but coil 6, which is the upper loop gate stays engaged upon starting the machine.

If one coil was locked on, I would suspect I would check out the specific 'Q' transistor on the driver board, but this issue seems more widespread as it's affecting every coil being driven from connector J116.

Any help, guidance, or attention of any kind if appreciated! Apologies if above was hard to read - I've been self-handicapped having friends much more gifted than me, but what a time it is to be self reliant!

#2 52 days ago

I'd check all ribbon cables first. Red stripe pin one each end. And not off by a row.

LTG : )

#3 52 days ago
Quoted from LTG:

I'd check all ribbon cables first. Red stripe pin one each end. And not off by a row.
LTG : )

Thanks for the quick reply, Lloyd. I got excited, as if it was as simple as a ribbon cable being connecting wrong, that would have been a huge relief. I reseated every ribbon cable, checked to ensure they were aligned with the pins, etc., but same issue. I understand ribbon cables can sometimes fail, which my be the issue here, but anything else to check?

Also, I noticed that one leg on U7 is jumped to U8 on the Power Driver board. Not sure if that is a hack and is part of my issue, or if it's considered normal.

#4 52 days ago
Quoted from MiamiRedSkin:

but anything else to check?

Did you check this ?

Red stripe pin one each end.

Each grey ribbon cable has a red stripe on one side. That goes to pin one on the circuit board. Both ends. Each board has a white "1" silk screened next to where pin one is and the red stripe goes to.

LTG : )

#5 51 days ago
Quoted from LTG:

Did you check this ?
Red stripe pin one each end.
Each grey ribbon cable has a red stripe on one side. That goes to pin one on the circuit board. Both ends. Each board has a white "1" silk screened next to where pin one is and the red stripe goes to.
LTG : )

Hi Lloyd -

I actually didn't know about the red stripe until I read your comment again and check it out. Red stripe on all ribbon cables are on 1. For good measure, I reseated all ribbon cables again to ensure they were aligned. Same issue

#6 51 days ago

Also, just swapped the ribbon cable going from the CPU to the Driver Board from my Scared Stiff, and same issue when all coils all hooked up, the left ramp diverted locks on and causes F103 to blow. If I disconnect the diverted, it moves to the next coil in the sequence.

#7 50 days ago

Still struggling bump

#8 50 days ago

I'd get a hold of the schematics and see if all the coils that are locking on are controlled by the same chip before the transistor. With J116 disconnected, do you have a short to ground on each pin of the board with the power on and off?

#9 50 days ago

Looks like U7 (74LS374) on the Power Driver Board feeds the data signals to all of your transistors/coils on J116. I'd start by testing U7 using this method: https://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit.

#10 50 days ago
Quoted from longwetsocks:

Looks like U7 (74LS374) on the Power Driver Board feeds the data signals to all of your transistors/coils on J116. I'd start by testing U7 using this method: https://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit.

Thank you both! Upon inspection, U7 is jumped to U8, and as that drives these coils, I’m thinking this is the culprit. Photos attached. This might be beyond my repair
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#11 50 days ago

Well that's a fun one. Also noticed there's a small jumper on pin 17 but that's beside the point right now. What's puzzling to me is that Pin 1 of U7 should be tied to the blanking signal while Pin 1 of U8 should be tied to Vcc. They have effectively tied what should be your blanking signal on U7 to Vcc which may be the cause of your coils being locked on. I'm not the most knowledgeable when it comes to blanking, so I hope someone else can back me up here. I wonder what broken trace they were trying to repair with that jump wire. You should have continuity from Pin 1 of U10 to Pin 1 of U7 and Pin 1 of U7 to Pin 1 of U4. If you're not comfortable tracing schematics, running jump wires, and possibly removing an IC to install a socket, you may want to the send the board out. But like you said, with us being quarantined, it wouldn't be the worst time to try and learn something even if you don't fix it.

#12 49 days ago
Quoted from longwetsocks:

Well that's a fun one. Also noticed there's a small jumper on pin 17 but that's beside the point right now. What's puzzling to me is that Pin 1 of U7 should be tied to the blanking signal while Pin 1 of U8 should be tied to Vcc. They have effectively tied what should be your blanking signal on U7 to Vcc which may be the cause of your coils being locked on. I'm not the most knowledgeable when it comes to blanking, so I hope someone else can back me up here. I wonder what broken trace they were trying to repair with that jump wire. You should have continuity from Pin 1 of U10 to Pin 1 of U7 and Pin 1 of U7 to Pin 1 of U4. If you're not comfortable tracing schematics, running jump wires, and possibly removing an IC to install a socket, you may want to the send the board out. But like you said, with us being quarantined, it wouldn't be the worst time to try and learn something even if you don't fix it.

Yeesh, this might be beyond my comprehension. I also have a history of doing more bad than good when it comes to more invasive boardwork. Might be a job for a pro

#13 49 days ago

Can you unsolder the wire from either U7 pin 1 or U8 pin 1 and give it a try?

#14 49 days ago

Pin 1 of U7 and pin 1 of U8 are both wired together via the board as are pin 1 of the rest of the LS374 on the board, so running the jumper is not doing anything to cause any issue.

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