Bad solenoid in Alien Poker questions [Fixed]

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Hilton
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Re: Bad solenoid in Alien Poker questions

Post by Hilton » Sun Feb 19, 2017 9:46 am

from what we found last night it appears the pre-driver (sorry, not sure what it is really called) that is just before/in line with the tip responsible for the coil of concern was pegged open. Definately the odd man out.

can someone educate on what this is actually called and what it really does. The smaller 3 legged can transistor just before the TIP.
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ralphwiggum
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Re: Bad solenoid in Alien Poker questions

Post by ralphwiggum » Sun Feb 19, 2017 11:02 am

Think of it like a switch turning on a switch. It is a gateway between low voltage logic and high voltage operation.

"The way the driving logic works is as so: the CPU, which is running the game ROM program, wants to energize a coil. It tells the a PIA (Peripheral Interface Adaptor) to turn on the appropriate coil. This in turn drives a 7408/7402 chip, which then turns on a small "pre-driver" 2N4401 transistor. So far this is all done with "logic level" 5 volts. Then the pre-driver transistor turns on a much bigger TIP120/TIP102 transistor. This final link in the chain is what ultimately completes the coil's path to ground, causing the 28 volt coil to energize momentarily."
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Hilton
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Re: Bad solenoid in Alien Poker questions

Post by Hilton » Sun Feb 19, 2017 11:39 am

Thanks TIm for the explanation.

With the bad predriver, is the likely culprit something else which then cause the predriver to fail? My thought was originally the diode on the coil, but now with that understanding of the separation of high voltage and the 5v and the predriver stage, I am not so sure.

In other words is there a likely root cause beyond the failed predriver?
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Re: Bad solenoid in Alien Poker questions

Post by ralphwiggum » Sun Feb 19, 2017 11:45 am

Usually, these smaller transistors get blown out by the bigger transistors they are tied to. While logic chips can go bad, they dont usually take out these smaller transistors. These smaller can also just flat out fail as well.

I have seen these larger transistors pass through voltage and take out the smaller ones, without blowing themselves.
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Re: Bad solenoid in Alien Poker questions

Post by Hilton » Mon Feb 20, 2017 10:27 am

thanks for the insight.

Noah > keep us posted.

I personally would likely replace both the predriver and driver even through the tip tested fine.

That is just me and I figure if I have the board out and the equipment all set up then why not.
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NoahK
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Re: Bad solenoid in Alien Poker questions

Post by NoahK » Mon Feb 20, 2017 10:43 am

Sounds like a plan. I ordered 10 of each transistor so replacing both sets won't be a problem. I'll also check the diode on the coil and replace that if that is bad as well.
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Re: Bad solenoid in Alien Poker questions

Post by NoahK » Wed Mar 01, 2017 9:08 am

Trevor and Moe came over last night and we replaced the two sets of driver and pre-driver transistors on the board. We also cleaned up and replaced the diode on the coil just to be safe. We powered the machine up and it worked, mostly. There was some weird behavior with the two drop targets where they were resetting out of order and would have problems resetting in-game; the coil would fire repeatedly but the drop target would not pop up. What we found was that we had switched the wires for these solenoids in the connector while testing and forgot to switch them back. Once we did that the game played just fine. Celebratory beers were had afterwards. Next step is to clean it up, learn how to wax the playfield, and give it a good stress test before MGC.

Thank you very much everyone who helped!
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Re: Bad solenoid in Alien Poker questions [Fixed]

Post by Hilton » Wed Mar 01, 2017 9:32 am

great news!!!!

I think this officially my first time I was beneficial on an online tech thread :)
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Chris K
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Re: Bad solenoid in Alien Poker questions [Fixed]

Post by Chris K » Wed Mar 01, 2017 9:36 am

Ain't nothing like the feeling of a freshly-fixed pinball table! Congrats!
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Re: Bad solenoid in Alien Poker questions [Fixed]

Post by cad-kid » Thu Mar 02, 2017 1:37 pm

congrats on the fix!
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Re: Bad solenoid in Alien Poker questions [Fixed More Better]

Post by NoahK » Fri Mar 10, 2017 11:16 am

Last night I figured out how to wax the playfield and was going to give it a night of play to ensure that it will survive MGC. Moe and Trevor came over to help with that. Unfortunately during the second game, the game reset and I got the boot problem that I mentioned in my original post. According to a troubleshooting guide I found, this is typically either due to a bad power supply or a connector issue. Looking at the power supply, some capacitors have been replaced and some not. The originals could be replaced, but we didn't have replacements on hand. We inspected the 40-pin interconnect between the CPU and driver boards. The female connector had been replaced recently and the solder joints looked good. Eric, you were right. The male pins on the CPU board were a different story. The pins were starting to corrode and the solder joints all looked bad. Below is a picture of the solder joints; the right 15 or so have been resoldered.
IMG_20170309_200919954.jpg
After Trevor resoldered the pins and we put the board back in, the machine booted up and played half a dozen games no problem. I still want to put a couple more coats of wax and give it some more playtime, but it is looking promising for MGC. :D
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Re: Bad solenoid in Alien Poker questions [Fixed]

Post by BigDaddyBanjo » Sat Mar 11, 2017 3:31 pm

Welcome to Pinball ownership Noal. If it ain't broke, you aren't playing it enough! Nice job jumping in and figuring stuff out!
Home Collection : Hobbit, Mustang, WPT, T2, BK, TMNT, F-14 + others on route with Madison Pinball at Schwoeglers, Pooleys, Alt Brew and Marias.
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