Williams Road Kings: some technical problems

diesel64

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Hello everyone,

I'm Kristof, I live in Belgium and I got into the pinball hobby only recently. :)


A couple of months I bought ago I bought a Road Kings that was working but the game wouldn't start. After replacing the column transistor that controls the outhole switch, things were working again.

Until yesterday. When I pushed the start button to start a new game, the machine went completely nuts (garbage on the displays, hum through the speakers, flashing lights, random resets,...), so I switched off the machine immediately.

When I opened the backbox, I noticed a fuse was blown. The fuse blew on the right side, not in the middle. I indicated the blown fuse on the photo below:

dsc0038rf.jpg


As far as I know, this is the fuse on the circuit for 50V non-flipper coils. Is that correct?

After removing the fuse and switching the machine off and back on for a couple of times, things were working again. (I haven't placed a new fuse yet because I'm out of 2.5A fuses. I will get more soon) The only things that were not working were the Upper Left Kicker and the Power Kickback (left outlane).

However, the machine did reset on some random occasions (about 2 times in 15 minutes). I don't know the cause of this.

Then, today I wanted to measure something with my DMM. I switched on the machine and wanted to put the black lead of my DMM behind the ground strap in the backbox. When I touched the ground strap, the machine started to go completely nuts again (garbage on the displays, hum through the speakers, flashing lights, random resets,...). The red lead of the DMM wasn't touching anything. I quickly switched the machine off and I haven't tried switching it on again, because I'm afraid of damaging anything.


Does anybody have an idea what could be the cause of all this?


Thanks in advance!
 
Last edited:
OK, I think I'm onto something here...


I focussed on the power supply. I disconnected the logic power and measured the lines of the power supply. Both 5V and 12V looked pretty stable and in spec.

However, after connecting the CPU board, I measured again. The 5V was still stable, but the 12V was a bit lower and fluctuating.

This picture shows the 12V line when the CPU is not connected:
12vwithoutload.jpg



This one shows the 12V line when the CPU board is connected:
12vwithload.jpg



Is this normal behaviour? Is it a good idea to replace the filter capacitor C10 and/or the power transistor Q5? Both are still original. Could this 12V issue be the cause of one or both of my problems (the resetting and the weird behaviour)?
 
Owkay... I removed the power transistor Q5, sanded the legs and put it back. This obviously changed the 12V line signal:

12vaftersanding.jpg



It's not perfect yet, but I don't know how it should be on a perfectly working System 11?

All I know is I just played for half an hour without any resets.

Would you still think it's needed to replace both Q5 and C10?
 
First off theres a reason for every fuse you should never run a machine with one missing.

I bet your resetting is coming from your PS Board plugin cables loose wire? or your connections are burnt?
 
i would replace that big grey capacitor first off.
then id take that flipper board out and see if theres any cold solder joints behind there and re-flow them.

then id ohm the coils to see if any are shorted, and manually move them to see if any are sticking.
 
Thanks for your suggestions!


First off theres a reason for every fuse you should never run a machine with one missing.

I bet your resetting is coming from your PS Board plugin cables loose wire? or your connections are burnt?


Hmm. I will inspect again, but I can't notice any burnt connectors. However, since I sanded the legs of the transitor, the game has only reset once (in about an hour of play). Before I couldn't play 5 minutes without resetting.


i would replace that big grey capacitor first off.
then id take that flipper board out and see if theres any cold solder joints behind there and re-flow them.

then id ohm the coils to see if any are shorted, and manually move them to see if any are sticking.

As far as I know, that big grey capacitor smooths the 18V for the lamps. It has nothing to do with coil voltages and it is a component that doesn't fail often (says pinrepair.com).

The flipper board is still original and untouched.

I have measured the resistance of the coils and I moved them manually. Everything seems fine.
 
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