Leaderboard

What a week I've had, one MPS2 specifically. Usual symptoms of no boot which was eventually solved by swapping out all the 20 pin chips around the CPU. To add insult to injury IC10 had also failed (TMS9902) so unfortunately the user is going to have to source one from somewhere. One thing did seem odd, on switch on there was no sound and the diag sound test was missing? Firing up an alarm did sound but it was quiet and didn't sound very clean. After much time wasting I realised I should have put my Worzel Gummage fault finding head on instead of my swap it out first head!! So a few wasted hours of swapping out audio o/p and synth chips plus going down many a rabbit hole I ended up doing some more diagnostics. Basically the output of the LM380 IC3 (8) was sitting at around 1.5v. These chips should have approx half the supply voltage on pin 8 and the inputs (2 + 6) are floating, well they were on this board. First head scratcher, this board is a revision B and instead of pin 6 being connected to ground it has C70 (0.1uF) to ground. Not sure I've ever noticed this before but the diagrams only show rev A. Next thing I noticed was any slight wisp of breath directed around C12, 14 and 15 brought the sound back to normal and then off again as the voltage on IC3 (8) rose to 12v. In fact any moisture in this area would cause the output voltage to vary. I've had this before and suspected tracking due to a dirty board. So off came all the components in that top right hand corner and a good clean was carried out. Before re-assembly I thought I'd just do some checks to make sure all was good....and it wasn't!! Applying the Ohmeter to the board and checking IC3 (2) I was seeing approx 3M Ohms to ground and considering the track was open circuit at both ends that wasn't good. Not sure why I tried the next thing but I put the iron on the hole for C14 and after about half a second the resistance went down to about a couple of hundred Ohms. Oh dear. Removal of the iron and the resistance would quickly climb back to a few megs. So the board had gone conductive inside. I could hear Andrew96 in my head saying 'I told you so' After all the work I'd done I didn't want to write it off so I thought I'd try something. Cutting the track by the via from pin 2 and routing a patch wire to two axial caps in place of C14 & 15 stopped the leaking voltages getting in the audio chip. These were fixed in place with hot melt glue and with everything reassembled all was good.

I'd have loved it si but I already have a carfield and jist aint got the room .

NOW who is "making coin" from poor poor collectors!

When I first come across the conductive board problem it was in the PC92 reset circuit. when the board was nice and warm it booted, but when cold (like the next day) the reset meandered instead of switching cleanly. oh the reply's! no one believed me! one member even said "conductive my arse" lol and of course my newly designed replacement reset board was just a con to get people to buy something that wasn't needed as a clean and replacement transistors of the reset area was all that was needed...... hope they are eating humble pie now lol Paxolin does indeed go conductive over time mainly its the conditions they been stored in over time. some are perfect, but some can be really bad! The PC92 ones I had which was bad came from project coins workshop and was sold off as a job lot and most showed the symptom. weather this is what they could not fix so they was stored.... or the storage conditions had caused the problem with conductive boards we will never know! but it does seem I was the only one ever to have PC92 reset issues and only one other board outside of that job lot since lol

Had a poke about today and found 2 broken connectors, one was on centre reel hence being erratic then not working this is why 3rd reel not stop as the sensors were not seeing movement and preventing cycle finishing.so I have had a few games and it works,and pays out.i do need a square button on top pannel as one is broken, will measure later.

Anyone that wants to know the full story I made the video I was also part of obtaining permission and I was there when they were removed, I got 4 myself.. I'm happy to tell the full story to put to bed some of the rumours.. Looks to be a bit of jealously ffrom 1 or 2 unfortunately.. The main thing is some were saved❤️

I posted that machine in the eletro club on facebook if you want to have a look on the comments regarding the mpu. Hear I'll save you the hassle.

Just completed a board which made me smile. Came in with the usual full service needed, so once that was done it was switch on time. Pretty much dead so checking the RESET which was good it was out with the RAM. With my spare test board it fired straight up and then using my new chip tester showed one of the RAM chips was knackered.👍 The other one was good and yes I did try it with another just to confirm it ran properly in the board. So now it was time to run through all the tests before going into the Cabaret machine for a soak test. First all triacs were firing, next all switches, sound working, alpha good, reels good......hmm no lamps! Inspected the board again and couldn't believe I didn't see this the first time. Looks like the plumber's been here! Once that was removed all the vias and the pads were missing on both sides. After a bit of patching, new rivets and lots of patience I arrived at this. With a new transistor in place all lamps were now correct.