Alltek MPU Woes

Longshot

New member
Joined
Apr 18, 2008
Messages
892
Reaction score
2
Location
Minden, Nebraska
A year and a half ago, I bought an Ultimate MPU from Alltek for my Bally Star Trek. Everything powered up (seven flashes). And so it sat until a week ago, untouched. I had a slew of minor fixes to go through, which are all fix but 2 major problems, 1 is identified.

The first problem, is that the game MPU resets when the ball triggers the out hole switch. A tech brought over an actual Star Trek MPU, which solved that problem. I tried to get him to "accidentally" leave the board, but he wasn't as forgetful as I had hoped.

The second problem baffeled my tech and I both. In game and during the switch test, certian switches activate certian soleniods (ones they shouldn't). The launch lane switch triggers the left bumper, drop target 4 triggers the right bumper, out hole switch triggers lower thumper and so on. It does this with both MPUs. And both solenoid driver boards my tech rebuilt. I also have a brand new power supply.

I assume the problem is in the wiring, but where do I start? Diodes, capacitors? It sounds like a couple wires pinched together, but I wouldn't know which wires to look at? Anyone ever see this before?
 
A year and a half ago, I bought an Ultimate MPU from Alltek for my Bally Star Trek. Everything powered up (seven flashes). And so it sat until a week ago, untouched. I had a slew of minor fixes to go through, which are all fix but 2 major problems, 1 is identified.

The first problem, is that the game MPU resets when the ball triggers the out hole switch. A tech brought over an actual Star Trek MPU, which solved that problem. I tried to get him to "accidentally" leave the board, but he wasn't as forgetful as I had hoped.

The second problem baffeled my tech and I both. In game and during the switch test, certian switches activate certian soleniods (ones they shouldn't). The launch lane switch triggers the left bumper, drop target 4 triggers the right bumper, out hole switch triggers lower thumper and so on. It does this with both MPUs. And both solenoid driver boards my tech rebuilt. I also have a brand new power supply.

I assume the problem is in the wiring, but where do I start? Diodes, capacitors? It sounds like a couple wires pinched together, but I wouldn't know which wires to look at? Anyone ever see this before?

Are these CPU-controlled solenoids or stuff where the switch is hardwired directly to them? Assuming they are CPU controlled, I'd start by running the switch test and looking for switches that the CPU reads as more than one switch. That could be caused by bad wiring or by problems on the CPU itself.

Do the same with the solenoid test - look for two solenoids firing together.
 
Are these CPU-controlled solenoids or stuff where the switch is hardwired directly to them? Assuming they are CPU controlled, I'd start by running the switch test and looking for switches that the CPU reads as more than one switch. That could be caused by bad wiring or by problems on the CPU itself.

Do the same with the solenoid test - look for two solenoids firing together.
In the solenoid test, only one solenoid at a time fires, just as it should. In the switch test, there are about 5 switches that fire unrelated solenoids (slam switch fires saucer, launch lane fires left bumper, drop target 4 fires right thumper, and so on). I have noticed that once in a while, quite a few switches read (just for a split second) the wrong switch number. But it is so fast I cannot catch the number it first reads.

Since this problem is consistant with two suposedlly working MPUs (Alltek and -35 rebuilt by a tech), and two rebuilt solenoid driver boards, I am assuming this is a wiring issue. I have also cleaned and checked all MPU and solenoid driver board wiring connections. I guess I am wondering if this sounds more like pinched wires (can't seem to find any yet), or could this be caused by a bad capacitor or doide on a switch? Is there a more likely cause for this?
 
I had a similar problem on my D&D pin. Playing the game I'd have random popper pops, locked balls would mysteriously unlock as multiball would start despite not hitting the correct targets.

Took me a while to find it but eventually found a spot on the playfield where the main trunk of wires were rubbing against a support for a popper's solenoid and had worn the insulation from the wires. They'd intermittently short to ground as solenoids fired.

An aftershot of where the problem is/was:


main.php


Maybe not your problem, but a possibility anyways
 
I had a similar problem on my D&D pin. Playing the game I'd have random popper pops, locked balls would mysteriously unlock as multiball would start despite not hitting the correct targets.

Took me a while to find it but eventually found a spot on the playfield where the main trunk of wires were rubbing against a support for a popper's solenoid and had worn the insulation from the wires. They'd intermittently short to ground as solenoids fired.


Maybe not your problem, but a possibility anyways

That's definitely sounding likely. It's not that the wires are likely pinched, it's that they are shorting.

Alternately, have you had a good look at the power supplies? I shouldn't think they were the problem, but if the supplies were a bit off, then it's not impossible to suppose that it could cause problems with reading the I/O lines.

Also, you indicated that you'd tried multiple MPU and driver boards. Have you closely examined the cables between them? If you had bad wiring to the MPU board, you might experience trouble.
 
That's definitely sounding likely. It's not that the wires are likely pinched, it's that they are shorting.

Alternately, have you had a good look at the power supplies? I shouldn't think they were the problem, but if the supplies were a bit off, then it's not impossible to suppose that it could cause problems with reading the I/O lines.

Also, you indicated that you'd tried multiple MPU and driver boards. Have you closely examined the cables between them? If you had bad wiring to the MPU board, you might experience trouble.


I have a brand new power supply with all new connections, so I ruled that out, and the tech and I went through all the connections and wiring on the MPU and solenoid driver boards. As far as I can tell, everything in the head checks out.
 
Back
Top Bottom