Repairing Williams Defender Power Supply

AndyD421

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Considering most people recommended I take this route, I am now fixing the original power supply in my Defender. I've already fixed the butchered wiring, etc, but am curious if the board is safe to hook up to the game with the current voltage coming out of it.

This is specifically in reference to the power supply board. If these are too far out of spec to run the game on, let me know. Also, I still don't know what type of voltage should be going into the marquee light and the monitor... that would help.

Here is what I know so far:

Defender Power Supply:

4J2- POWER OUTPUT

Accepted Voltages posted from manual:
PIN 1: -5 VDC
PIN 2: KEY
PIN 3: +12 VDC
PIN 4: -12 VDC
PIN 5: +12 VDC
PIN 6: +12 VDC
PIN 7: GND
PIN 8: GND
PIN 9: GND
PIN 10: GND
PIN 11: N/C
PIN 12: +5 VDC
PIN 13: +5 VDC
PIN 14: +5 VDC
PIN 15: N/C

Actual Voltages from my game:
PIN 1: -4.98 VDC
PIN 2: __
PIN 3: +11.92 VDC
PIN 4: -14.80 VDC
PIN 5: +14.37 VDC
PIN 6: +14.37 VDC
PIN 7: ___
PIN 8: ___
PIN 9: ___
PIN 10: ___
PIN 11: ___
PIN 12: +5.17 VDC
PIN 13: +5.17 VDC
PIN 14: +5.17 VDC
PIN 15: N/C

4J3 - COIN DOOR POWER

Accepted Voltages posted from manual:
PIN 1: +6.3 VAC
PIN 2: +6.3 VAC
PIN 3: +27 VDC
PIN 4: N/C
PIN 5: Key
PIN 6: GND

My voltages:
PIN 1: +5.0 VAC
PIN 2: +4.78 VAC
PIN 3: +33.30 VDC
PIN 4: ___
PIN 5: ___
PIN 6: ___

I really hope someone can help me out... look forward to any and all responses.

-Andrew
 
The +5V regulated is a little high (+5.17V). You might want to replace the LM723 voltage regulator and see if that brings it down a little. Ideally, it should be between +4.97 and +5.05VDC. +5.17VDC will start to burn up the RAM chips, they are very sensitive to overvoltages.

On the diagram, you will see some of the voltages listed as unregulated (or unreg). This means that they are not passed through a voltage regulator and so will tend to be high. When these games were new, wall voltages averages 110 - 117VAC. It now tends to be 124-130VAC so some of the unregulated voltages will be a little high.

ken
 
Thanks for the replies!

I actually checked to see what was coming out of the wall, and the output side of the EMI/Line Filter showed me 118 VAC.

I really don't want to fry the RAM board. In fact everything you've told me so far makes sense. When I bought this game, the previous owner bought it from someone who mentioned it needing a ram board, and it came with a stack of about 3 of them in various stages of repair (Not including the one already in the game)
 
You could check the voltage at the RAM chips. I'm betting.....by the time the juice flows out of your power supply, through the harness, and into the "RAM board".......it'll be a bit lower.

(I'd bet barely over 5 volts...if that)

Edward
 
You could check the voltage at the RAM chips. I'm betting.....by the time the juice flows out of your power supply, through the harness, and into the "RAM board".......it'll be a bit lower.

(I'd bet barely over 5 volts...if that)

Edward

I actually haven't hooked the power supply up to the actual game yet. It was DOA, and I didn't see any lights coming from the PS. I pulled it along with the entire power harness, and got to work on fixing the hacked wiring, reflowing old solder and improving connections, etc.

That is something to think about though. Trust me, I'm dying to get this game going... but I've rushed things in the past, and it's lead to me taking a game or two to the dumpster out of stupidity. I'd rather play it safe on this one. :)
 
Unloaded?

You really shouldn't test a power supply that is unloaded. The rectifiers need load - it is how they deal with all the power.

No load means the rectifiers have to dump all the excess power as heat, which can shorten or in a worst case condition, extinguish their life.

If you have test resistors hooked up, it will be okay. I hope you did.
 
You really shouldn't test a power supply that is unloaded. The rectifiers need load - it is how they deal with all the power.

No load means the rectifiers have to dump all the excess power as heat, which can shorten or in a worst case condition, extinguish their life.

If you have test resistors hooked up, it will be okay. I hope you did.

Test Resistors? You've lost me.

I didn't keep it on long, btw. Just long enough to get voltage reads from the proper sections (2 Mins TOPS).

Could not having it hooked up to the game really fry something? If so, then how the hell are you supposed to fix a power supply without frying the entire game??

I am officially confused... :(
 
Last edited:
Test Resistors? You've lost me.

I didn't keep it on long, btw. Just long enough to get voltage reads from the proper sections (2 Mins TOPS).

Could not having it hooked up to the game really fry something? If so, then how the hell are you supposed to fix a power supply without frying the entire game??

I am officially confused... :(

here, I'll help you:

You really shouldn't test a power supply that is unloaded. The rectifiers need load - it is how they deal with all the power.

No load means the rectifiers have to dump all the excess power as heat, which can shorten or in a worst case condition, extinguish their life.

If you have test resistors hooked up, it will be okay. I hope you did.
 
You really shouldn't test a power supply that is unloaded. The rectifiers need load - it is how they deal with all the power.

No load means the rectifiers have to dump all the excess power as heat, which can shorten or in a worst case condition, extinguish their life.
No load = no current drawn = no power to dissipate... It is absolutely fine to run a linear power supply with no load.
 
No load = no current drawn = no power to dissipate... It is absolutely fine to run a linear power supply with no load.

I agree, linear's are fine without a load......but, some still won't regulate properly without a load.

Now.....switch mode power supplies.....do not run those very long without a load.

At this point........you've got a case of chicken little;)
The sky is not falling.....plug that sucker up and take an actual loaded voltage reading. The 15-30 seconds it'll take to do this won't hurt anything.

Edward
 
I dont see it mentioned here but the OP also asked about voltages going to the monitor and marquee.

Both should be 110-120VAC but the monitor is wired through an isolation transformer (or it should be if its not).

The output voltages from your power supply all look fine and as a few others here mentioned will be slightly higher because there is no load attached to it. WMS power supplies are famous for having perfectly fine +5 but when you attach a load to it the +5 drops in half or less.... To get an accurate measurement you should always test the supply (linear and switching) with a load.

Load resistors would simply represent a typical load that a board would put on a supplies voltage. I have no idea what sort of load all of the boards in a defender puts on the supply so I couldn't tell you the ratings of the resistor. I can tell you that it cant me much because I think that power supply tops out at 5Amps on the +5 or is it 7, I really dont remember.

If you dont want to risk the boards you could probably get away with using a few 44/47/555's across the 5 volts outputs and a 161/194's across the 12-14 volt outputs.
 
You guys have inspired me to hook it up to the game for 10-30 seconds to get proper power readings.

I'll be leaving in 2 hours to do this, so if someone with higher knowledge thinks this is a REALLY bad idea, I can be stopped.

I never realized that the load can bring down the voltages... Hopefully 10 seconds does not blow anything up.
 
I never realized that the load can bring down the voltages... Hopefully 10 seconds does not blow anything up.

So long as your +12 reg and -5 dont spike really high you'll be fine. But, that usually doesnt happen.
 
So long as your +12 reg and -5 dont spike really high you'll be fine. But, that usually doesnt happen.

And thats funny to hear. I had another thread going where I was going to replace the original power supply with a switching one because of "all the bad things I heard" about the originals.

I don't know where I got this idea, but I was sure that these old Williams power supplies would self destruct and send massive voltage down the lines to fry these games in a heartbeat..

I guess that is almost like the rumor with the duramold cabinets, huh? I still haven't seen pics of a monitor being launched out of the cabinet, so I guess we can all sleep better at night. :)
 
I did say "usually." It does happen though. I've seen MPU boards with all of the RAM IC's tops blown off and it was all because the -5 regulator shorted and passed the unreg -12 to the IC's.

I go the switcher route personally but I understand the desire to keep these games original.
 
IT WORKS!!!

...sort of.

All voltage going into the game was PERFECT. 12.98 instead of 12 was the biggest error.

Now, I turn the game on to repeating sounds and other garbage. I think the RAM board is messed up. At first the game would sometimes boot up with some weird double screen type action, but then it just started booting to a highly messed up "Initial Tests Indicate Ram Error" screen.

I guess it's ram board time?
 
IT WORKS!!!

...sort of.

All voltage going into the game was PERFECT. 12.98 instead of 12 was the biggest error.

This supply outputs two 12VDC lines.....one is regulated.....the other is not. 13VDC is totally fine for an unregulated 12 volt line.

Edward
 
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