Stern I/O board debugging

YellowDog

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Donor 2011, 2013
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I have a newer Stern (Ripley's) with an I/O board issue. The MOSFET at Q16 (lower right flipper) fried and when I went to look at it, it had previously been repaired by the worlds worst solderer. All the traces had been lifted and solder blobs replaced the traces. That much I can fix.

Based on a recommendation on Pinside I replaced the STP22NE10L (NTE2396) with an IRL540N which is supposed to handle higher amperages. But it still doesn't work. At least now it is not locked on, it just doesn't respond.

What I need to know is what are the voltages supposed to be on the three legs. I am getting 75v on the middle leg of Q15 and 12v on the middle leg of Q16. Ground (leg 3) is reading 0 on both and I don't remember what the first leg was reading.

If this ring a bell with anyone, please let me know.

Also, if there are any recommendations on repair facilities, I am open to shipping it out. I just want it fixed right.

Thanks.

ken
 
Since I am not getting any info, does anybody have a place that repairs Stern boards they want to recommend?

Thanks.

ken
 
I don't have the manual in front of me but I believe that is a Whitestar board? If so, I would try replacing U2 before sending it out for repair. Most likely Q16 shorted and possibly fried U2, R16, and C247. C247 and R15 are unlikely but U2 would be the first on my list. One would think that Q9-15 would have issues as well if U2 was the problem, but I have seen stranger things.
 
Update: The parts came in last Friday. I had to order a bunch of other stuff (caps for monitor capkits and a few other parts I was getting low on) in order to get passed the $25 minimum order. The Post Office tore the bag they shipped the parts in and guess what was the only thing missing? The 74HCT273s :mad: :mad: :mad: . Now I have to order again. I am trying to get them to let me just order those parts and not dick with the $25 minimum. We'll see how successful I am.

This is absurd.

ken
 
If they won't work with you, let me know. I am pretty sure I have a few hanging around here and I would be happy to send some your way. Let me know!

Quentin
 
If they won't work with you, let me know. I am pretty sure I have a few hanging around here and I would be happy to send some your way. Let me know!

Quentin

Thanks for the offer. I got an email Tuesday that they had just found my email (apparently they don't look at their sales email address as that is the one they use to send confirmation emails out). They resent the missing chips for free. That is good customer service. I had offered to pay for the chips an shipping again as long as I could not have to get to the $25 minimum again and they just shipped them.

I swapped the chip out last night. No change. :(

So I started tearing it apart. The middle pin on Q16 (would be a gate on a transistor, but I think MOSFETs call it something else) was reading 23V. I tried Q15 and the middle pin was reading 73V. So I metered the coil, it was still good. The diode was still good. I pulled the board and checked the repair job on the traces. Everything checked out. :(

Finally started tracing everything and the fricking fuse was blown. :mad: It wasn't that way the first time I worked on it. Then I remembered that a couple of pin guys took a look at it (the Ripley's is at The Game Preserve not my house) after I first diagnosed the blown MOSFET, so they must have popped the fuse while they were tinkering with it.

So the moral of the story. Always check the fuse even when you are sure it's not the fuse. Especially when you are getting very different voltages on the middle pin of the MOSFETs.

Now I just have to undo the damage they did to the end of stroke switch. The flipper is chattering at the top if the stroke.

But at least it is working. Thanks to everybody that made suggestions.

ken
 
(Hopefully) Final Update: The MOSFET burned out again. Despite being a much heavier duty version. This time I walked the entire component chain. The IC was fine, the coil was fine. The capacitor was shorted and the diode on the coil had come loose. The fix: replaced the MOSFET and the capacitor, soldered the diode back down and adjusted the end of stroke switch. And (knock on wood) it is playing like a champ again.

Moral of the story, if it ain't working 100% keep looking, you ain't fixed it yet.

Thanks everybody for all the suggestions.

Now to make that little idol pay for laughing at me........

ken
 
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