Playmatic Chance MPU Problem

[ChadTower]

I am guessing the coil is shorted and it's only a matter of time before it eats the driver.  Could also be the resistance is within the margin of error on his meter or he has it on the wrong range.

[DarkSide]

Its nice to hear everybody thinks im a moron, maybe this is my first pinball machine, but still

Coil is working, or at least the target go up and down as they should, im thinking its my dmm thats the culprit here, but its also just a cheap one but has so far been good enough for my use.

Let me try to describe how im measuring it, dmm on, set at 200 ohm, probes on the terminals on the coil.

Got everything else fixed today, targets work, ball dispenser, rebuilt the Decoder board.

[DarkSide]

Just checked a few mixed coils from the machine and they all show the same on my DMM, so it looks like my dmm cant be used for measuring coils.

The Williams Coil on the Pop bumper is a G-23-750, and should be 3R9 in Resistance according to http://flippers.com/coil-resistance.html   

[DarkSide]

Drill a hole in the front of your cabinet and run a string to the drop target reset bracket.  Yank on it when you knock the targets down.

Also, invest in a self-ranging DMM.  3R9 in flippers.com language means 3.9 ohms.  What's the lowest setting on your DMM??

Lowest is 200 ohm, so it looks like i need a new DMM, if we say 3.9 ohm, i would suppose that its in the same rating the drop targets coils are.

[DarkSide]

You sir are brilliant.

Found my old dmm, and checked the coils, both came in at around 4.6 ohm, so i took a drill and at slow speed cleaned out the sleeve that was melted, fitted it to the machine, and guess what, it works.

Its a bit slow compared to the other coil, but it can be a matter of adjustment.

Both sets of drop targets work.

[DarkSide]

http://edesigns.dk/pins/droptarget.m4v Short video.

Yes i know the playfield is dirty

[TopJimmyCooks]

Awesome.   Nothing like some results. 

PBJ's an asset to this forum for the acerbic wit.  (Oh, and the pinball repair tips, too.)

[DarkSide]

Found the last two legs for the machine, and got it mounted, also took a few fast games and the machine works.

Still got a few lamps that does not work, and the plunger is not good either, i think the spring has gotten to weak.

[DarkSide]

Well not all is good, it happens a bit to often that the relays triggers an extra time, and the machine thinks its the 2 or 3 ball, when its really the first.

If its a relay fault, or something else, that i dont know yet.

[DarkSide]

You was right, it was that switch, but i do have a bad relay will need to get that changed.

Cleaned the plunger. but its still not good, half the time it does not work.

Will try and order one of those coils, just to have a spare, blew out a fuse today because of a bad connection, got that fixed, also fixed the sound, but i think i will disconnect that again

[DarkSide]

Something fishy is going on.

The Ball dispenser keeps activating every time the slingshots are activated, but only the slingshots, any thoughts on that ?

Short Circuit, PCB failure, Contacts ?

[DarkSide]

It does have a test program, and the strange thing is when activating that every coil on the playfield activates as it should.

But the ball dispenser keep trying to kick a ball every 10-15 seconds, it should only happen once, it smells a bit like a MPU failure ?

Edit: Sometimes when i turn on the machine it also kicks the ball out, so logic failure sounds possible, but it only activates once.

[DarkSide]

If it's engaging every 15 seconds that the game is on and playing, even without you knocking the ball around, you've got a board problem.  If there's a diode anywhere in the wiring associated with that switch, I'd replace it first.  It could be on the actual switch, it may be on a board inbetween the wiring and the MPU....

If that doesn't do it, my advice would be to defeat the ball trough switch connection at your MPU and see if the coil is still engaging.  It's sounding increasingly like you do have a board problem, but this way you can be 100% sure.

I will try and disable that switch tomorrow and see what happens, when game is playing the ball dispenser only activates when the slingshots are active, nothing happens when the pop bumpers, drop targets, flippers are used.

Its only on the test program it keep activating the ball dispenser every 10-15 seconds, can a dead diode really make that kind of problem ?

[ChadTower]

Way to check that is to really gap that ball trough switch or snip a wire to one of the leads. 

I usually just put cardboard between the contacts for this.

[DarkSide]

Okay a little update, took the switch out of the circuit, and it still does the same, tried activating the switches under the playfield, and it only happes with the switches for the slingshots, also just by activating them without the coil is active, followed the wire to the MPU at connector 03, but so far no solution.

Edit: Disconnected the wire for the scoring switches for the slingshots and now the game runs, but i cant see how a set of scoring switches can make the ball dispenser freak out, unless there is something wrong with the MPU board, ive also found out that its not just the ball dispenser freaking out when it happens, its all the coils that activate for a short period of time.

[DarkSide]

Im positive its a board issue, as it is right now i can't even start a game without the ball dispenser fires 3 times, and then game over.

Guess that was the end of that machine, i can do some board repairs, but i have no idea on where to look.
 
Edit: Changed the Decoder board, nothing changed, as soon the scoring switches for the slingshots are connected the coils start acting up.

[DarkSide]

Okay thats strange.

Had the game in test mode, pushing the switches, they should all give a different number, but those in the slingshots do not, they give 13, and that belongs to the ball trough switch

The slingshots should give 43, not 13.

Thats properly why the game thinks the ball was lost, and tries to shot a new one.

Edit: Any tips on how to fix that, wires looks good, no short circuits, so i guess its somewhere in the MPU or Decoder ?

[ChadTower]

Ah well, if all the coils are firing you've got a bad row or column in your switch matrix.  Make a note of which ones are activating and compare it to the switch matrix, you should find that they're all in a line together.

That. 

[DarkSide]

The Switch Matrix yes, but i have no idea where to find out where it is in this machine.

Can a defective switch matrix make the switches think they are on another location ?

13 instead of 43.

[ChadTower]

Can a defective switch matrix make the switches think they are on another location ?

13 instead of 43.

Yes, that's exactly what it could do.

[DarkSide]

Yes, that's exactly what it could do.

Any suggestions on how to figure out how the switch matrix works on something like a Playmatic ?

[DarkSide]

Pop out your driver board, test all the switch transistors with your DMM on the diode setting.  Replace the transistor that measures differently than the rest of them.

 

Maybe im stupid now but im not so sure if its transistors controlling that switch matrix, i think its 40xx.

There is a MPU board, a Decoder board, a Thyristor board for the lights, and a few relays.
http://edesigns.dk/Chance/IMGP7949.jpg

[ChadTower]

If 40xx are doing the switching then those chips are just diodes/transistors in a common ground package.

[DarkSide]

If 40xx are doing the switching then those chips are just diodes/transistors in a common ground package.

The question is just where i should look, there is around 30 40xx chips on that mpu board.

I know the switches for the Slingshots are connected to 03 on the MPU board, what leads to a 4072, then to a 4016, and a few more 40xx chips.

[DarkSide]

Clothes pins on the fuse holders!  I love it.  That's an insanely tidy backbox... good ol Playmatic.


Yeah, you're right, looks like your switches are controlled by 4042's?  Trace out the one connected to your trough switch and see if it's the same one connected to your slingshot switches.  You need the find the component in common.

 

Yea im not proud of those, but new ones are on order, gonna change all the fuse holders.

Will try and trace it out, should be possible

Edit: Traced the connection to the ball trough switch.

Ball trough switch connects to A on the MPU board, from A to 4081, then 4013, and 4011.
Slingshots connect to 03, then 4072, to 4016, to 4011, im not sure if im reading that schematic right, if anybody can take a look i would appreciate it.
 

[DarkSide]

Well i wanted to work on the machine today but im all out of 4042's, typical.

Hope changing those will fix that switch matrix problem.

[DarkSide]

Still not fixed, but game plays, it can just happen random that the machine thinks ball is lost and tries to shot a new one, even in the middle of a game.

It still seems to happen most often when the slingshots are used.

[DarkSide]

With the prices from here i would guess close to 6-700 USD.

The game is in Denmark, i just cant provoke the fault to show it self messing with the wires, connectors, playfield, only if i touch the score switch for the slingshots.

But as i said it does not happen all the time.

If i disconnect the score switches for the slingshots everything is working, well except its not scoring points when hitting the slingshots, so bad connection i really doubt it.

[DarkSide]

The slingshots are independent, and it does happen with both of them, or im not sure if thats the right way to write it.

It happens when touching the score switches under the slingshots, also without activating the slingshot itself, but it only happens at random.

I can play without problems, but if the ball activates the slingshot score switches to many times in a short period of time the machine thinks ball was lost, lets shot a new one.

Edit:

It does the same with all the switches in that part of the matrix, but they do show the right number in the test program, any ideas ?

[DarkSide]

Same idea I had before... replace the components associated with that part of the matrix.

Did that already, but same fault.

Can i ask you to take a look at the schematic, and tell me what you would change ?

[DarkSide]

Bit of an update.

Found out today the score switches and ball switch are on the same matrix, score switch is on 03, and ball switch is on 3B, both connected to the same 4072.

But i did change that, 3 times, also changed what was next in line a 4016, and a bunch of 4081 and 4042.

[DarkSide]

Got it !

Finally, it was a floating input, missing connection between 2 resistors, machine is working 100% now.

[ChadTower]

Nice!   

[DarkSide]

So what other Playmatics have you got to mess with?  I'm really intrigued by these things...

Only my Chance, got a Party also but its missing a lot of vital parts so im just breaking it for spares.

Got to get rid of those two Playmatic's and start on my Jurassic Park instead.

[DarkSide]

Short video: