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Possible WPC Board & LM339 Issue

Calimori

Calimori

Staff member
10 Years
Joined
Mar 15, 2012
Messages
4,277
Location
Luton, UK
Alias
Calimori
Not sure where is best to post this, Tech, Wanted or "I'm an Idiot section".



Yesterday I decided to strip the ramps and underside from my Addams and do some more cleaning. A full rebuild left me with two missing screws for the THING kickout switch, a switch that did work anyway. I decided that I would cable tie it to some cables to keep it out of the way and order a new switch.

The game all worked fine but a problem with THING lead me to go want to adjust his enclosure and for quickness I didn't switch the power off :oops:. I didn't notice but I knocked the cable tied switch and as I was shutting the machine it touch the THING kickout solenoid and shorted the machine.

Test mode gave me a ground short in all but one switch row, then as I started to trouble shoot the number got less leading me to believe it is not all shorts but the LM339 at U20. I have used the usually help and repair guides and concluded the following.

If I disconnect switch connection J212 on the WPC board and THING under the playfield, I get no ground short errors but loads of other switch issues. However, switch test mode gives a short on ever row for the switch tested.

Before I replace the board does anyone have any other tests to try?



Does anyone have a WPC board (TAF compatible) that they want to sell me? I am not asking for a lend in case there is another problem with my machine that would damage another board.



I am not confident enough to replace the LM339's on the board just yet, I would like some practice on something a little less valuable. I am willing to literally pay for my stupidity and I am not happy to now have no machines at home to play.



I have already spent 3hrs in the naughty corner for being an idiot and not switching the machine off. I got away with it so many times that I forgot the consequences. Let this be a lesson for you all, cover lose wires and switch your machine off or it will go bang.
 
Shame you are gonna have to wait a while to put those new found moves into practice
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Why don't you send your board to someone with an Addams so that they can test the board for you ?
 
Andrew Stockdale' date=' post: 1694538 said:
Why don't you send your board to someone with an Addams so that they can test the board for you ?
Click to expand...

Mainly timing, I am without a machine and that rubs in the mistake. A replacement board could mean I am playing again by mid week.

If someone is not too far away from Watford (M25/M1 junction) and is happy to try a swap then I will come to them. It would the the quickest way to check the board and the U20 chip.
 
You almost certainly fried U20 LM339. They are easy enough to socket and replace. Many tend to be socketed anyway as someone has made the same mistake in the past ! The only question is what other damage has it done eg shorted the thing coil or more damage on the CPU board. I'm happy to replace the U20 for you if you wish to send me the board.
 
Very kind of you to offer to repair/check them for me. I am just waiting on a reply from someone local to me from the Yahoo groups about dropping them over to him to do U20. My lack of a fix for two days is making me a little jumpy and my patients is going out of the window.

Checking up, chip U20 is a ULN 2803N and that is the first likely culprit. U18 and U19 are LM339 and they could also have been toasted. Sadly, they are not yet socketed, so a quick swap is not possible.

The THING coil has been tested, then reconnected and it appears to not be shorted or shorting and is working. The bad switch has been removed and the offending wired taped up, there are not other identified shorts in the wiring for the switches so I think it is just the chip/s.

I am going to order some bits so I can practice PCB soldering, I don't think the tip of my soldering iron is small enough either. I have learnt a serious lesson, more about checking better for lose wires.
 
John Oliver from the UKPinball Yahoo group is going to take a look tomorrow and hopefully solder in some new chips.

Which for me, is very good news.
 
If you are going to have a bash at board repair, get a decent soldering iron first. One that you can change the tips on.



Andrew.



Calimori' date=' post: 1694575 said:
Very kind of you to offer to repair/check them for me. I am just waiting on a reply from someone local to me from the Yahoo groups about dropping them over to him to do U20. My lack of a fix for two days is making me a little jumpy and my patients is going out of the window.

Checking up, chip U20 is a ULN 2803N and that is the first likely culprit. U18 and U19 are LM339 and they could also have been toasted. Sadly, they are not yet socketed, so a quick swap is not possible.

The THING coil has been tested, then reconnected and it appears to not be shorted or shorting and is working. The bad switch has been removed and the offending wired taped up, there are not other identified shorts in the wiring for the switches so I think it is just the chip/s.

I am going to order some bits so I can practice PCB soldering, I don't think the tip of my soldering iron is small enough either. I have learnt a serious lesson, more about checking better for lose wires.
Click to expand...
 
John has already had to do this to his ST:TNG and sounds like he knows his stuff. However, I have a new soldering iron arriving at the weekend and I will be heading into the loft to get some old computer PCB out for practice. I might never need to repair one again myself but I hope to be better equipped next time.
 
John is indeed one of the good guys. Very pleasant to meet another pinball collector who is willing to offer help.

He showed me his Pinball shack and then got down to cutting off chip U20, a ULN 2803N, he then put on a socket and we fitted a new chip.

A logic probe arrived today so I had a chance to give the other chips a clean bill of health. So with the job done, we then played some ball.



I then got home, fitted the board and all the ground errors were gone. I think the bookcase opto's are toast but the rest of the errors appear to be working out. THING flip opto might be dead too, plus THING Up opto but more testing needs to done.



I can now play a game
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.
 
Good news that you have the board fixed. Without looking at my Addams or the manual, is there an opto board under the Playfield that controls the optos ?

If so, the LM339's on this could have blown which would give you multiple opto errors.



Andrew.



Calimori' date=' post: 1694647 said:
John is indeed one of the good guys. Very pleasant to meet another pinball collector who is willing to offer help.

He showed me his Pinball shack and then got down to cutting off chip U20, a ULN 2803N, he then put on a socket and we fitted a new chip.

A logic probe arrived today so I had a chance to give the other chips a clean bill of health. So with the job done, we then played some ball.



I then got home, fitted the board and all the ground errors were gone. I think the bookcase opto's are toast but the rest of the errors appear to be working out. THING flip opto might be dead too, plus THING Up opto but more testing needs to done.



I can now play a game
smile-1.png
.
Click to expand...
 
Yes, there is a 7 Opto control board under the table that has gone funny too. Has two LM339's that appear to be fried via a simple logic probe, I think the actual optos are probably ok.

New, small, soldering iron tip arrives tomorrow for the my new temp controlled soldering iron. I will then do some practice on a spare board John gave me, then give it a go. I have two sockets to fit and then some spare chips. Wish me luck.
 
You will be fine. Have you got a solder sucker ? Makes it a lot easier to add new components if you have clean holes in the board.



LM339's are little buggers. They can cause all sorts of problems and can be quite difficult to test for faults at times. Their performance seems to deteriorate after a few years and they start to strobe their signal to the CPU board.

I bought a job lot (100) so just tend to socket and replace them if I suspect one is iffy.



Andrew.
 
I have a sucker and I am not afraid to use it.

Where are people buying the sockets from? John kindly gave me a few but I would like some more.
 
I did some practice chip removal on an old board.

Used a dremel to cut the legs and remove the chip body. Then I used an old electric solder iron to heat the legs, and using a kebab stick to pick the hot legs out.

Then more iron heat and a sucker to get a clean solder ring. Work so well I decided to start on the actual opto board. My only mistake on the first chip was I didn't properly support it when I flipped it over and soldered the legs, this means it is not flush with the board. The second one went in a charm.



Board back in the machine and the Bookcase optos works and THING does his flip things. All errors caused by my mistake are now sorted, I have learnt a lot of new things and don't feel like quite an idiot.
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Excellent news. Good man.

I suspect it won't be your last encounter with LM339's in the years to come.



Andrew.



Calimori' date=' post: 1694712 said:
I did some practice chip removal on an old board.

Used a dremel to cut the legs and remove the chip body. Then I used an old electric solder iron to heat the legs, and using a kebab stick to pick the hot legs out.

Then more iron heat and a sucker to get a clean solder ring. Work so well I decided to start on the actual opto board. My only mistake on the first chip was I didn't properly support it when I flipped it over and soldered the legs, this means it is not flush with the board. The second one went in a charm.



Board back in the machine and the Bookcase optos works and THING does his flip things. All errors caused by my mistake are now sorted, I have learnt a lot of new things and don't feel like quite an idiot.
smile-1.png
Click to expand...
 
Great to know you have it sorted and learnt along the way. Best of all you have your machine back and playable again.
 
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