(Topic ID: 287310)

DATA EAST PPB Board Coil lock on

By McPin54

5 months ago


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  • 16 posts
  • 7 Pinsiders participating
  • Latest reply 6 days ago by PinballManiac40
  • Topic is favorited by 1 Pinsider

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#1 5 months ago

I feel like a novice here. I've never had a coil lock on that i haven't been able to fix. Working on a Lethal Weapon 3. Left drop target bank locks on. This coil is associated with mpu/driver and PPB board. Ive narrowed it down to the PPB board. After looking at the schematics I can not find the culprit on the board. Checked all diodes and resistors. Swapped out relay also. On Schematic, it looks like there is no transistor thats related to it on the PPB board. I checked all transistors anyway and the all measure good.

I know its on the PPB board because I swapped it out with another and works fine.

What am I missing on this board? Where could my problem be? Any help is much appreciated.

Thank you in advance

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#2 5 months ago

Morning bump

#3 5 months ago

On the CPU Board.

The main drive transistor is Q41 Tip 102, Q33 is the predriver 2n4401. I would replace those two items along with the Diode 1N4007 on that coil.

#4 5 months ago

I love to try learning things reading these posts. If swapping in a different PPB board eliminates the problem, why would a fix on the CPU board be needed? I ask because problem vanishing after swapping PPB boards would have made me think (perhaps erroneously) that the problem must be on the PPB.

#5 5 months ago
Quoted from chad:

On the CPU Board.
The main drive transistor is Q41 Tip 102, Q33 is the predriver 2n4401. I would replace those two items along with the Diode 1N4007 on that coil.

Thats where I started first. Both pre driver and Q41 are good. Problem goes away with new PPB board. Problem is 100% on PPB board I just don't know where

#6 5 months ago

You may

Quoted from McPin54:

Thats where I started first. Both pre driver and Q41 are good. Problem goes away with new PPB board. Problem is 100% on PPB board I just don't know where

Just reread and saw you did this. I missed it initially.

#7 5 months ago

Have you looked over every inch of the bad board? Look for solder bridges, a stray piece of metal shorting something it shouldn’t, a broken fuse holder with one side flipped towards the one next to it shorting out.....

How did you check the diodes and transistors? If you have a coil locking on I’d suspect a bad TIP36. Not sure which one on a LW3 but I’m finishing up two of these boards for other data east games. Each had bad TIP36 devices. Most of the time a diode check on the meter can help weed out bad parts. It’s not perfect though. Any parts that I even suspect as being bad I’ll pull and use a transistor checker to compare against a known good part. You can get some decent ones on eBay for under $30.

#8 5 months ago
Quoted from Robotworkshop:

Have you looked over every inch of the bad board? Look for solder bridges, a stray piece of metal shorting something it shouldn’t, a broken fuse holder with one side flipped towards the one next to it shorting out.....
How did you check the diodes and transistors? If you have a coil locking on I’d suspect a bad TIP36. Not sure which one on a LW3 but I’m finishing up two of these boards for other data east games. Each had bad TIP36 devices. Most of the time a diode check on the meter can help weed out bad parts. It’s not perfect though. Any parts that I even suspect as being bad I’ll pull and use a transistor checker to compare against a known good part. You can get some decent ones on eBay for under $30.

I actually have a transistor meter. I just used dmm this time. I replaced multiple ceramic resistors and 4 big boy diodes. I measured all components. Bridge measures. .44 to .49 I'm good there. I may buy another relay. Maybe my replacement relay is bad. I know pic shows no fuses. I just took them out. They ar good.

Really scratching my head on this one

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#9 5 months ago

I follow the rule that a (BJT) transistor that tests bad is bad but one that tests good is not necessarily good. I have a TIP102 that passes the diode test on a DMM but when used in a board is shorted from collector to emitter.

If you've checked everything else and can't find a measured failure then I would remove the TIP36C and replace it. You can also get incorrect readings from a component that is in-circuit. Ideally you should test the component when isolated. That board is a single sided board so there's no danger of pulling through holes as there are none.

#10 5 months ago
Quoted from DumbAss:

I follow the rule that a (BJT) transistor that tests bad is bad but one that tests good is not necessarily good. I have a TIP102 that passes the diode test on a DMM but when used in a board is shorted from collector to emitter.
If you've checked everything else and can't find a measured failure then I would remove the TIP36C and replace it. You can also get incorrect readings from a component that is in-circuit. Ideally you should test the component when isolated. That board is a single sided board so there's no danger of pulling through holes as there are none.

Ran through all the components and they all checked out good. I'm thinking my back up relay is bad. I cant find a 7a 30vdc relay anywhere. Is there a substitute?
It's what the schematic calls for

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1 week later
#11 5 months ago

Was not the relay?

I'm stumped

2 months later
#12 85 days ago
Quoted from McPin54:

Was not the relay?
I'm stumped

Based on what I read, I'm stumped too. Long shot here, but your headers look new. Any chance there's a solder bridge underneath from some drip through...or does this problem pre-date those? My brain keeps heading back to a solder bridge. Have you checked continuity across those pins?

1 month later
#13 34 days ago
Quoted from Goonie:

Based on what I read, I'm stumped too. Long shot here, but your headers look new. Any chance there's a solder bridge underneath from some drip through...or does this problem pre-date those? My brain keeps heading back to a solder bridge. Have you checked continuity across those pins?

stepped away from this one but back on it. LOL
No solder bridge. I put in another ppb board and coil still locks on.
I just replaced Q40 again and still locks on. I am going to replace the drive transistor again...
I am wondering if it is further up stream....maybe a chip?

thank you

#14 34 days ago
Quoted from chad:

On the CPU Board.
The main drive transistor is Q41 Tip 102, Q33 is the predriver 2n4401. I would replace those two items along with the Diode 1N4007 on that coil.

Left back drops are Q41 as chad mentioned. Q40 is on the right bank drops.

So why had you replaced Q40?

#15 34 days ago
Quoted from PinballManiac40:

Left back drops are Q41 as chad mentioned. Q40 is on the right bank drops.
So why had you replaced Q40?

Sorry. I ment 41

Yes the wire is off the pin in picture For testing

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4 weeks later
#16 6 days ago

Does R74 to R76 measure close to the same resistance?

You made sure you did not have a solder bridge between any of the transistor legs after soldering?

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