Parts arrived yesterday morning, frustrated as I was out all day and all night, and really keen to get on with this. Today I had to take my Mum to the hospital for a consultation. So delayed again. I must admit by the time I got home early afternoon my enthusiasm for taking the board out etc. has waned.
A cup of Yorkshire tea and a fish finger sandwich and I'm revitalised!
So,
1. I/O board out, carefully unplugging the 14 wiring connectors, and ensuring I'm not statically charged. Board onto a makeshift Static mat (silver foil - earthed).
2. Desolder two of the MOSFET transistors and check and clean the board. I notice one of the track spots has lifted away, but it's only to hold the leg of the transistor on the underside of the board, and doesn't connect anywhere - the topside of the board does and is intact. Also note one of the other tracks has partially burnt away but there is enough there to solder the new leg onto. (This is the transistor that controls the ring magnet - looks like it got very hot at one time.
3. Test the removed Mosfets. The one for the left flipper has continuity between Gate and Source - so looks duff. The ring magnet one has no continuity across any of the legs, but I suspect this is blown and will never switch on.
4. Carefully solder in the 2 new parts, trim the pins and check that electrical connection is made to the PCB trace wires on the lower and upper sides of the board. I made sure I and the board and parts were electrically grounded and even unplugged my soldering iron to solder on the pins. Pretty sure I have done a good job of keeping these safe. I could have wound some thin wire temporarily around the three legs, but I felt I'd done enough.
5. Double check the new parts, soldering, connectivity and for shorts. Clean off excess flux on the board between the joints and tracks.
6. Check the rest of the board and components, all looks ok.
7. Check the fuses in the board, some are the wrong rating, so replace correctly as per the manual. Some are blown - Ring Magnet originally specified as 3A, but later advisory is 4A, so fit that.
8. Replace board and fit and check all 14 wiring connectors
9. Double check
10. Triple check
11. Put back box back together for a moment as I realsie I've not replaced the diode on the left flipper coil.
12. Remove glass and raise the PF - a bit trickier than usual as this pin has Pinstadium lights which need to be removed and placed into the pf, and care needed to lift the pf out past the strip magnets on the sides of the cab - there are also mirror blades fitted, so this is a very tight squeeze.
13. Cut off the diode - I wanted to test it just out of interest, but managed to drop it in the machine. Took me 20 minutes to find it! Tested it - looks fine - but I'm not unhappy - I needed to test it to do a thorough job and I now know that the culprit is more likely the transistor I've just replaced. I also now know for future ref that diodes are less likely to fail than transistors.
14. Solder on a new diode, double checking I've got the polarity right.
15. Replace 3A fuse on underside of pf near the flipper - it was blown of course.
16. Put the pf back together and re-setup the pinstadium lights.
17. Remove backglass and DMD/speaker board so I can see the I/o board completely and can see all the fuses, especially the ones that power the ring magnet and the 50v coils general.
18. Dare not switch it on ----- I need another cup of tea to build up some courage and maybe I just need to check everything one more time.........
19. Switch on at mains plug - no bang
20 Switch on using the main on/off switch under the cab.
21. BOOM!!!!!
22. Only joking - seems to be powering up all ok........no left flipper on immediately, no fuses glowing or blowing..........
23. Games boots ok - but no playfield lights????
24. Switch off quickly
25. Go check all those 14 board connectors again and then the fuses in the board. I noticed earlier that some fuses have been pushed in too far and too hard by someone previously and the fuse holders have become deformed. I pull out the fuse for the 18v lights and reseat. Also check the 2 connectors that drive the lamp matrix, these now connect vi an OCD driver board so check the wiring to that. All looks good.
26. Power On #2 - all ok, with lights this time. Suspect it was the fuse not seated properly.
27. Test left flipper - all ok
28. Play a game to test the ring magnet. Takes me two lost balls before I hit a clean shot to the ring and YES! The ball is held by the ring magnet, and then released as intended after the mode sequence intro plays out.
29. Re-assemble the backbox and the pf glass. Re-test once more. 100% fixed.
Job done.
Things I have learnt today:
1. Take your time and only start a job like this once you are in the right frame of mind and have relaxed.
2. Plan out what you are going to do and how you are going to do it.
3. Get all your tools out ready to go. Spares out too.
4. Work slowly and with care
5. cut off old components first - it makes de-soldering a lot easier.
6. Use a solder sucker too.
7. Earth up if handling static sensitive devices
8. Check, check and double check.
Things I have learnt from this overall experience:
1. Manual is your friend - make sure you get a manual with each pin you buy. If one is not included, ensure you can download one or purchase one elsewhere.
2. Fuses - don't use the wrong fuses - Buy in a good stock of the common types. (I'm also investing in 3A and 5A circuit breakers - courtesy of
@myPinballs )
3. Don't go testing out bits of your Machine that already work using the test points on a board just for the hell of it. I am sure this is what blew my left flipper transistor. Instead just use test points to check that a non working part is indeed non working.
4. Diodes - like fuses - cheap parts - get in a stock of these so you can easily replace ones on coils that are not working properly.
5. Think about what is or isn't happening in the game, this logically points you to the probable cause.
6. Don't be afraid to tackle a board repair. Especially power Transistors, these are quite likely to be fail points. When replacing a part, do some research to find out if the exact part number is the best or whether there is a better alternative part that others have used instead. In my case I bought the original replacement part £5.99 as it is obsolete and hard to find. I then discovered that the replacement part is not only better and more robust, but also far cheaper £1.40.
7. Do not despair! Most things are fixable and if you can't fix it, there are people you know who can.
Thanks to everyone above for advice and support - really helped me successfully sort this out. THANK YOU!