Need help with some Defender problems

lmdave

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I have an early series PCB, D8356, and they are no batteries in the upper right sockets. Are these needed for normal gameplay? What polarity do the batteries go in?

Besides the batteries, Here are a few of my problems:

When I finally got my Defender to power up, it stayed on the Book keeping screen.

If it shows Coins 0000, then I can do the switch from 28 back to 1, sometimes have to do it twice, and it will go into the game over mode.

Sometimes it shows Coins ????, if it does that then I can't get into it.

While in game mode, I have no sound. When I first started playing with it booting up, I heard some start up sounds and beeps, but no that I have game play I have no sound. (EDIT: I did see another thread of someone replacing the 6808 chip and their sound started work, so I'll look into that, but any other ideas are welcome)

During the game being on about 5 minutes, the "All time high" list goes from scores to all "???", and my settings change. (number of men, difficulty, etc..)

D8356.jpg
 
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The batteries save the scores and game settings. I think Defender will always boot to the book keeping menu when they're dead or missing. I thought there was some type of marking on the battery holder or nearby on the board indicating polarity. On Williams pins, all the +'s face the same way, which is different from most newer stuff.
 
you have an original power suppy ?
if so, are all three LED's lit ?

just because they are lit doesnt mean they are correct
if one or more is out, could be the power supply needs rebuilding

try advancing through ALL the book keeping settings and see if it goes into the attract screen at the end
 
I do have an original power supply, and LEDs were on. I hope it wasn't just bad voltages causes the problem.

I already decided to bite the bullet and just sent all four PCB boards in for diagnosis and repair.

I tried batteries in the slots first all left and the screen went black on power up , not even bookkeeping, the tried all right and same thing, took them out and got to the book keeping screen. Cycled to option 28 and back to 1 and got the attract mode. Played a game or two with no volume.

I also bought a switcher PS from arcade parts, just incase, I plugged the 15 pin into that and adjusted the knob until the 5 v was good and it wouldn't even go to the attract mode, I got diagonal lines across the screen. Went back to the original PS and got the book keeping again. But flakly settings that would change by themselves and no sound.

Now I'll just have to wait to get the boards back now that I boxed them
Up.
 
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One of the common issues with old Williams battery holders is that the contacts get corroded very easily and then they don't supply enough voltage to keep the CMOS alive. They also get bent putting batteries in and out and don't make solid contact and the same thing happens.

The best thing is to check the voltage at the CMOS when the game is powered off. Pin 22 is the + voltage an pin 8 is the - voltage.

ken
 
While my boards are out I'm looking at what I should have looked at first, the power supply. I didn't initially Do a thorough check of the voltages. (I'm new to arcade repair)

Anyway, without the boards connected can the PS be diagnosed?

I'm getting weird things. For example, the +12 and -12 unregulated circuit, when power is applied to the PS I get +12, but 0 on the -12. But with power off, I get +12 and -13 from the charge held in the caps.

I also my LED on the -5 went out, that whole circuit is dead now from the components I checked, it was working before.

I ordered the rebuild kit and BR3 but I don't think it has the Q2 transistor to cover all the components of the -5.
 
It is always difficult to diagnose the power supply boards without having them right in front of me. Bob's rebuild kits were based on what was going wrong with them 10 years ago and while that still covers about 70% of the cases, I have seen quite a few that have other issues as the rest of the components age.

If you are getting 0V on the -12V line, it sounds like BR1 is half shot.

Q1 rarely goes bad, but it can be substituted with a 2n3055 which can be obtained at most Radio Shacks.

If you find that you would rather not bother with rebuilding the power supply, there are several people on the boards here that rebuild them for a nominal fee. Dokert and I rebuild both Defender and Joust style power supplies.

ken
 
OK, I feel stupid. I just tested the fuses and turns out it was just fuses F4 and F5 were blown. All voltages are reading correctly now.

Well that eliminates the power supply.
 
I just my board back from repair. Everything seems to be in working order now.

One last problem I have is the volume. Even when I turn the volume all the way down, it's still a little too loud. Any ideas, or do I need to change the pot?
 
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