In Progress Lost in the PAC MAZE... Another Obsessive Restoration

[carl lawrence]

Had something like this when I bought Medusa back form the dead.
When I change the TIps on the sol board I had to change the diode s as well , because sometimes the TIps take out the diodes on the board too !

 

[Nedreud]

Had something like this when I bought Medusa back form the dead.
When I change the TIps on the sol board I had to change the diode s as well , because sometimes the TIps take out the diodes on the board too !

I usually replace the diode when I replace the transistor. And the 330R resistor too. In this case I'm 99.9% certain the driver board is good. I sure I've got a fault on the actual plafield itself, either duff or missing coil diodes, or a short/loose connection in the wiring.

 

[Jay Walker]

DRD may well have it, Peter. The slingshots are subject to the solenoid expander, but have ended up fitted with 'normal' coils, unlike the bumpers or target reset coils. Coils using three terminals were Ballys' method of establishing the additional diode network for the expander - Williams used a special board to do this, so that ordinary coils could be used.

 

[Nedreud]

2 4-October -2016
FIXING EXPANDER SOLENOIDS
So, in my quest to fix the GATE solenoid I discovered I've got coils half firing all over the place! In Solenoid Test Mode I can see that sometimes 2, 3 or even 4 drop-target reset coils are "twitching" when some other coil that is part of the SOLENOID EXPANDER circuit is being activated. To make this crystal clear to myself I got out my virtual colouring pens and coloured the appropriate wires on the coil schematic:



+43VDC comes onto the playfield down the BROWN (60) wire. This feeds the 3 flipper coils directly and onto the 1 Amp Slow Blow fuse for the rest of the coils on the playfield. Out of the fuse the wire changes to YELLOW (30) and feeds 5 more coils directly (OUTHOLE KICKER, GATE, TOP LEFT SAUCER KICK LEFT, TOP LEFT SAUCER KICK RIGHT and RIGHT SAUCER). The yellow wire also feeds the AS-2518-66 SOLENOID EXPANDER BOARD, which is mounted on the underside of the playfield, on Pin 9. By default, that is, when the solenoid expander is OFF the +43VDC exits the expander on Pin 7 down the GREY (90) wire to provide power to the following 7 coils, all of which are required at any moment during gameplay:

• LEFT THUMPER BUMPER
• CENTER THUMPER BUMPER
• LEFT SLINGSHOT
• RIGHT SLINGSHOT
• LEFT 4 DROP TARGET RESET
• RIGHT 4 DROP TARGET RESET
• TOP 3 DROP TARGET RESET

When the solenoid expander is switched ON the +43VDC comes out of Pin 5 instead on the GREY/RED (91) wire providing power to these coils:

• LEFT 4 DROP TARGET #1
• LEFT 4 DROP TARGET #2
  
• LEFT 4 DROP TARGET #3
  
• LEFT 4 DROP TARGET #4
  
• RIGHT 4 DROP TARGET #1
  
• RIGHT 4 DROP TARGET #2
  
• RIGHT 4 DROP TARGET #3
  
• RIGHT 4 DROP TARGET #4

Notice that these coils are not essential during gameplay - in this case they're for the individual drop-targets. It's not possible to fire 2 coils that are driven by the same Q transistor at the same time. There would be a delay to wait for the first trigger signal to complete, switch the expander (more delay, it's a relay after all) and then switch the same Q transistor on again.

Looks closely again at the above schematic and notice that all of the coils powered via the solenoid expander have an additional diode on the input to prevent any power travelling back up the supply wire. This is CRITICAL and something I was not aware of! Coils in these positions are usually of the 3-lug type, not because they have 2 windings like a flipper coil, but because the extra lug is used to affix this extra diode. To use a standard 2-lug coil a diode simply has to be placed on the input first before connecting the wire to it.

Anyway, technical lesson over, on to fix my problem. First fix I did on this game was to replace the burnt STERN coil on the left-hand slingshot. I happened to have an old spare Bally coil and just replaced like-for-like. Also notice int the photo the other slingshot has a replacement coil too:



It's obvious these are both standard 2-lug coils and therefore missing the extra diode required by the solenoid expander circuit. To fix this I simply removed the +43VDC wire from the lug next to the banded side of the fitted diode (GREY (90) for both coils) and soldered on a 1N4004 diode with the band closest to the lug. I then reattached the wires to the other side of the new diode:





This isn't an ideal permanent solution as the leads on the diode could break off eventually through mechanical fatigue, but for the moment it will do. I put the game back into Solenoid Test Mode and all the solenoids are firing correctly with no cross-talk or random firing of the non-default coils powered via the expander.

WOOHOO!

Well... except the GATE coil still isn't working... but now that one more Gremlin has been liquidated I can move on

 

[Jay Walker]

Is that the case in play, Peter?

With the gate coil being comparatively weak, it may not have an adequate drive pulse during the solenoid test.

Just noticed the date on the invoice from Replay Leisure Equipment is dated 23 October 2013, almost 3 years ago to the day! Wonder what it looked like back then? I also wonder what £245 of labour got you? Assuming that's five hours at £49/hr. Would that be about right?

In this case, a nasty dose of solenoid difficulties..

 

[Nedreud]

With the gate coil being comparatively weak, it may not have an adequate drive pulse during the solenoid test.

Not seen the gate some much as jitter during play. And nothing during solenoid test. As it's a continuous solenoid it should be obvious when it's operating, like the FLIPPER ENABLE RELAY. And when I ground it manually it makes a snap healthy "snap!" as the mech opens and closes. I'm now beginning to suspect the control signal from the MPU (which should be good, it's an ALLTEK) but will need to break out the oscilloscope to see what's going on. As a test I can swap the wires going to pins 8 and 11 so that the FLIPPER DISABLE signal is controlling Q17 for the GATE instead of Q15 for the FLIPPER ENABLE RELAY (the point here being that I know the flipper enable/disable is good and works in both play and test modes).




I will also replace the missing Q19 and R47 that have been robbed from the COIN LOCKOUT circuit to see if that works either. Here are my AS-2518-22 boards, MMPM (top) and the one from PARAGON (bottom) that was working but now has a dead +5V regulator:

 

[stevebm1]

if you need a 5v regulator there are some here on ebay:

http://www.ebay.co.uk/itm/302099280505?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

[Nedreud]

if you need a 5v regulator there are some here on ebay:

http://www.ebay.co.uk/itm/302099280505?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

£1 each?!?!?! Bargain. Bought 10 just to be safe.

If you search eBay for either LAS1405 or LM323 or 74H05 you find hits for these obsolete devices being sold for £10, £20, even £30 each! One seller, "LittleDiode", who stock a lot of NOS components and can have good prices, are doing these for £35.99! Cheapest I found was around £2.95 each... but from China so could be polished turds.

Thanks @stevebm1!

 

[DRD]

No idea whether I need the 5v thing or not. Never replaced one in my life. But it looks like there is a stampede here so I bought some

 

[stevebm1]

£1 each?!?!?! Bargain. Bought 10 just to be safe.

If you search eBay for either LAS1405 or LM323 or 74H05 you find hits for these obsolete devices being sold for £10, £20, even £30 each! One seller, "LittleDiode", who stock a lot of NOS components and can have good prices, are doing these for £35.99! Cheapest I found was around £2.95 each... but from China so could be polished turds.

Thanks @stevebm1!

I thought they were a good price!,I bought some 2 weeks ago and they turned up a lot quicker than the 3 month wait from china,any luck on those backbox hinges yet mate?

 

[Nedreud]

No idea whether I need the 5v thing or not. Never replaced one in my life. But it looks like there is a stampede here so I bought some

I've only ever hacked one off a spare board to fix the one for PARAGON. Now of course I have a board with no rectifier. The rest of the board could be shagged but it looks ok and very simple to fix - and I've got 5 or 6 of them! It always seem to be this 5V regulator that fails and there is no modern equivalent. You can hack in a BUX84 but it's not the same package, the legs have to cross over each other and the tab must be insulated because the TO-3 is a conductive case.

I thought they were a good price!,I bought some 2 weeks ago and they turned up a lot quicker than the 3 month wait from china,any luck on those backbox hinges yet mate?

I was tempted to buy the whole lot! Last time I bought a load of MC6800 CPUs and posted them on here there was such a stampede from other people on here the seller pulled the listing as they obviously realised they could have been selling them for a lot more. Hopefully others on here will grab the last remaining 2 sets of 5. £1 each is a total bargain for these. The seller has all sorts of interesting old electronic and computer junk. Maybe they're clearing out an old workshop?

 

[Nedreud]

This one is turning into a real brain-bender. Just turned it on for a couple of quick games and halfway through ball #2 all the lights and displays go out, and all the solenoids except the flippers stop working. The sound module continues to play the background sound but no switch triggered sounds. I must have some real flaky connections or an utterly **** +5V supply. Or the ALLTEK is ****ed! Unlikely but not impossible. Still haven't got to the bottom of the GATE problem either, although I did spend some time with the oscilloscope. I managed to trace the continuous solenoid data lines PB5 to PB7 on pins 5 to 8 respectively of connector J4 on the ALLTEK, but didn't see any change on PB4 for when the GATE should be triggered in Solenoid Test Mode. If that's true it means the ALLTEK isn't sending the signal on PB4 when it should. Again, this seems unlikely but not impossible. I need to get the ALLTEK on the bench. And the AS-2518-22 regulator module will get a rebuild/overhaul too...

 

[stevebm1]

the pins in those old connectors can crack,I had to replace about seven on a project star trek im working on at the moment.I had a problem with voltages not hitting the mpu despite the rectifier test points reading ok and it turned out to be crappy connectors,despite looking fine until you looked at them closely under the magnifying glass

 

[Nedreud]

The headers pins on the ALLTEK should be ok. But as you say everything else is well in the frame of suspicion! And it's another game with ****ty IDC connectors. I hate IDCs with a passion. A rage! A fury!!! They really are terrible. The only improvement they offer is faster assembly times for manufactures. Considering how many connections there are in a pinball it's easy to see why manufacturers made the switch, desperate to reduce production costs down to the last cent in the war against video games. In every other respect they are utterly inferior to the original crimp/solder Molex KK connectors.

Right. Rant over

Time to stop arsing around piking this and that. Just need to pull it all out and fix everything properly once and for all.

 

[Dave2084]

My pacman has a similar issue. The game plays normally except when any of the ghost drop target knock downs are fired the leftmost one fires as well. It is not a board fault.

I've just been playing it single player for now as the drop targets don't get reset between balls for one player.

Wish I'd seen those regulators, I need 4 already and the seller is local to me.

 

[DRD]

Probably the solenoid expander board issue again. All the coils associated with the solenoid expander circuit need diodes on them

 

[Dave2084]

Probably the solenoid expander board issue again. All the coils associated with the solenoid expander circuit need diodes on them

Already checked that, everything is as it left the factory. These are a PITA to take off which is why I've not fixed it but I suspect one of the diodes has gone short.