Williams System 6 Blackout Lock-on

vipe155

Active member
Joined
Jul 31, 2010
Messages
550
Reaction score
41
Location
Florida
I am new here, and joined to see if I can get some feedback on a problem I'm having with my oldest pinball. I don't have anyone in the area that knows much about arcade machines at all.

The pinball is a Williams Blackout. It worked fairly well a few months ago, then had a time when I noticed a slight burning smell. I discovered one of the coils had locked on and was burning, turned the machine off, and didn't bother trying to fix it until now. I have read up on System 6 machines and their issues, and have corrected some things.

I found that a several of the pins in the 40 pin interconnect had lost their tension, and two had disappeared altogether. Also, the transistors for the locked on coil (TIP120) was cracked. I replaced the 40 pin interconnect with new parts, and the transistor with a TIP102 and also replaced it's predriver transistor. Turned the game on, and the coil that was locked on was fine (I replaced the entire coil with a new one), but now a different coil was locked on (lower target bank). So I replaced the transistor and predriver on that, and now it's fine but the ball return coil is now locked on.

Is it possible that several of the transistors or predriver transistors for these coils have gotten damaged in a chain-like failure, and I need to go through each one, or is something else to blame?
 
I was thinking about that, but since the other half of the solenoids (9-16) are fine, I didn't think it would be a fried PIA chip since that one chip controls all the solenoids. I can unplug the first group (1-8) and the game goes into attract mode with no issues. Even so, I guess that could very well be it.

It's possible that the eject hole (original burned coil), drop target bank and return solenoids were all locking on at once, but I just noticed each one at a time.
 
You should be testing the transistors instead of just replacing them. Anything is possible once the interconnect goes south. It's possible that caused the PIA to lock those driver circuits on and fried them. The only way to really know is to test your way through the circuit.

It is possible for the PIA to have individual shorted outputs but I wouldn't suspect that first. The best way to troubleshoot this problem will be with Leon's test ROM and the MPU out of the game.
 
Here's my suggetion, if you want to take the full systematic rundown of the regular solenoids.

Pull all the connectors for the solenoids off the board, and turn the game on. Check the PIA outputs to see if any of them have +5v coming out of them. This is pins 2 thru 17 on the PIA. The only pin you should see voltage out of is pin 17, which is the coin lockout solenoid. Any other pins from this group showing voltage mean it's the PIA that's activating the coil.

If the PIA tests good, then move on to the 7408 logic chips at IC's 1, 2, 3 and 4. On all of these chips, it's pins 3, 6, 8 and 11 on these chips that are the coil outputs. If the PIA was bad, then run this test anyway after you replaced the PIA.

Of course, test ALL the transistors as per the info on Clay's site before just replacing them.

.........

This is all assuming that you've already confirmed the power supply 5v output is good, and already did new connectors for the logic output on the power supply, as well as the logic input on the CPU board. Always replace these connectors if they are original at the first hint of an oddball problem that doesn't make sense.

-Hans
 
I pulled the connector for the solenoids 1 - 8, which is where the locked on ones reside, and the machine boots up fine and goes into attract mode. I don't know what that means, but it would seem that something is wrong with that group. I will test all of the transistors in that group and replace whatever is necessary. I guess I can try testing the PIA chip. Any suggestions on how to get that thing out if I need to in the future?
 
How good are you at soldering, think you're up to a 40pin IC socket?

Easiest way to get it out is to get a fine pair of clippers, such as Xuron micro-shears, and just snip all the legs. Then de-solder them individually. If you try to do the whole chip intact when removing it, it's a good chance of damaging the solder traces.

And don't just solder a new chip in. Put in a socket, so you never have to do it again.

Same holds true for the 7408 chips, though they are much easier to replace I find.

-Hans
 
Just a quick update. I bought a DMM for the first time today, and tested the transistors on the driver board. The only one that was below spec. (.4 to .6) was the locked on one at the outhole return. The predriver for it was fine according to the DMM. So, I replaced that TIP120 and now the game starts up in attract mode with no locked on coils. Even so, it will not start a game, and the drop target coils do not pop the drop targets back up.

How do I use the DMM to test the PIA? Like what settings and where do I test it at?

Thanks everyone for your help so far.

***Update to the Update: Is there any reason why a start button wouldn't work? As I had said, press start and the machine won't begin a game. Well, I went into diagnostic/adjustment mode, and I can't change any of the settings in there with the start button.***
 
Last edited:
Any other switches that test as bad? or just the start button?

Check other switches in the same row and column. If any of the coin switches are good, and if the right drop target switch is good, then the board is likely good and time to move on to the switch itself. If those switches test as bad, we'll work on that later.

I'd start looking at the back side of the switch itself, see if the leaf blades are closing properly. Make sure the wires are connected still. You can try pinching a piece of paper between the switch contacts and rubbing it back and forth to clean it, you don't want to use anything more aggressive than just paper as it's got gold plated contacts.

Also test the diode on the switch, though usually I just replace those as they are so cheap. you can get a reel of the 1N4001 diodes very cheap via ebay..... IIRC I paid $4 shipped for 100 of them.

Could also try re-seating the switch connectors on the driver board, see if that helps.

-Hans
 
Just a quick update. I bought a DMM for the first time today, and tested the transistors on the driver board. The only one that was below spec. (.4 to .6) was the locked on one at the outhole return. The predriver for it was fine according to the DMM. So, I replaced that TIP120 and now the game starts up in attract mode with no locked on coils. Even so, it will not start a game, and the drop target coils do not pop the drop targets back up.

How do I use the DMM to test the PIA? Like what settings and where do I test it at?

Thanks everyone for your help so far.

***Update to the Update: Is there any reason why a start button wouldn't work? As I had said, press start and the machine won't begin a game. Well, I went into diagnostic/adjustment mode, and I can't change any of the settings in there with the start button.***

One of these days, I'll start this process on my Blackout.

Check the ground connector on the start button leaf switch. If that checks good, then check the continuity for the switch wire. If that is good then check the whole loop (start wire, switch, ground return). If that shows good, then you will need a logic probe to make sure the signal is getting through to the PIA.

It may just be a dirty switch. Clean with a white business card or a white index card. Do not use sandpaper. The contacts have a thin gold plating on them and sandpaper will take it right off. It will clean the contact, but over time it will arc and pit and fail again. If it is really dirty, put a drop of isopropyl alcohol on the paper to help clean the contacts.

ken
 
To test the PIA you want to set the DMM to read DC voltage, or even better if it has a logic feature set it to that.

The ground lead on the DMM can go anywhere that's ground, I usually clip it on the metal frame that the board mounts on for this test. Then check on pins 2 thru 17 with the positive lead. If the PIA is activating a coil, a pin will show +5V (logic high). If the PIA is not activating the coil it should show no voltage (logic low). Pin 17 should usually be activated, as that's the coin lockout coil which is always usually on when the game is on, but not always.

-Hans
 
One of these days, I'll start this process on my Blackout.

Check the ground connector on the start button leaf switch. If that checks good, then check the continuity for the switch wire. If that is good then check the whole loop (start wire, switch, ground return). If that shows good, then you will need a logic probe to make sure the signal is getting through to the PIA.

With any of the switches in a pinball machine you can't dump them to a ground on one side, they need to be run back to the driver board via the correct wires and connectors on both sides of the switch. They aren't DC or AC circuit switches like most people are used to, they are logic switches. It's a whole different animal to deal with.

-Hans
 
Well, I don't know what happened. I got the machine to start a game, in which it started to randomly score things on it's own. I turned the machine off, then back on, and now none of the solenoids work. I went into diagnostic mode and ran through the coil test, and none of them fire in it.

Maybe this is a chip problem now? I'm not sure what is going on here. I guess it's a start that none of the coils were locking on anymore.
 
Could also be one of the usual suspects. The Scanbe sockets are just trash, cause all sorts of problems. Same with the 5v power connectors between the PSU and CPU boards.

Dealing with essentially the same thing on a Firepower right now after it warms up.

-Hans
 
Quick note: If you have dealt with repeat burnt coils and drivers, do yourself a favor and pull all fuses and verify they are the correct rating.


Like others have said, you might be having switch matrix problems. You need the chart that shows the whole switch matrix. Then you can tell which switches are related.
 
Well, I don't know what happened. I got the machine to start a game, in which it started to randomly score things on it's own. I turned the machine off, then back on, and now none of the solenoids work. I went into diagnostic mode and ran through the coil test, and none of them fire in it.

Maybe this is a chip problem now? I'm not sure what is going on here. I guess it's a start that none of the coils were locking on anymore.

You're shooting in the dark until you have a known good 40 pin interconnect. I kind of skimmed the thread but you haven't replaced that yet, right? (EDIT: Yeah... it's right in your first post. Nevermind :p)

I would try some fresh EPROM code too. I had a Gorgar that showed some symptoms like that and new code fixed it. Still... the preventative maintenance stuff is a good idea and pretty much required before doing any real troubleshooting with intermittent or weird problems.

Looks like you've got some good help so far. You'll have it fixed in no time :)
 
Last edited:
Well, I don't know what happened. I got the machine to start a game, in which it started to randomly score things on it's own. I turned the machine off, then back on, and now none of the solenoids work. I went into diagnostic mode and ran through the coil test, and none of them fire in it.

Maybe this is a chip problem now? I'm not sure what is going on here. I guess it's a start that none of the coils were locking on anymore.

You probably blew a fuse which drives the driver PCB, At least that happened to me once when I was replacing a transistor.
 
I see you stated you replaced the 40-pin interconnect - did you replace both sides or just the pins on the mpu? Have you tested the legs of the PIA as suggested to make sure it is ok?

I would also re-check the switch matrix as suggested, it could be something crossed or a closed switch - I had a similar problem with a sys-6 and after replacing the interconnect I found that I had a bad switch on the coin door that shorted out an entire row. If the start button doesn't work I would check everything on that row.

You're getting close...
 
Yeah, I did change out the 40 pin interconnect. Per the repair articles, I've only replaced the female end as the male end looks fine to me.

I'd have to check again, but I think that when I tried the legs of the PIA, 17 gave a reading of ~4V. The other pins 2 - 16 were low.
 
Back
Top Bottom