Stargate

I have my Defender game working 100% but I've been playing around with the cabinet. By chance I saw a Stargate game (non-working of course) come on eBay at a decent price (okay, $250) that was local, so I put in my bid and waited 10 minutes to see if I won it (I told you it was by chance). So now I'm the new owner of a non-working Stargate game.

I went to Linden NJ (about 30 minutes away) to pick up the game early Christmas Eve morning with one of my daughters. The game was in the shape it was advertised so no complaints there. We hauled it home in the Suburban (it's really good having a Suburban when you need to move video games).

So the Stargate is in the basement right next to the Defender. My priority now is to get Defender put back together, I'll deal with the restoration of the cabinet later. Since Stargate uses the same monitor as the Defender (a GO7-CBO), I was able to swap monitors to see if the Stargate monitor was working. The good news is that the Stargate monitor is good but it does need a cap kit. So the problems are deeper (I suspected that since there was no sound during the POST) and will require some work.

So I just ordered a standard set of supplies when dealing with a Williams game, first a GO7-CBO cap kit and a "get well kit" for the linear power supply. Yes, the Stargate still has it's original power supply - no switching, and I'm going to keep it that way if at all possible (by the way the supply LEDs are all lit, so the supply probably isn't the problem). I also ordered a set of RAMs, the 4116's seem to go out quite commonly with these boards.

The cabinet of the Stargate isn't too bad. Like most cabs there are big holes from where lock bars were installed to secure the coin box. I have to rework the power cord. My plan is to use an IEC power entry module like I did for the Ms Pacman.

High Score for Defender

I did some more work on the Defender game today. My first priority was to get the high score kit installed. This is another item I purchased from Bob Roberts (www.therealbobroberts.net) that replaces the three AA battery holder that comes stock on a Defender board.

Invariably having AA batteries on a board causes all kinds of problems when the batteries leak. For some boards the damage is extensive and renders the board unusable, but for mine the damange was rather minor. But the battery back didn't work as the terminals of the battery holder were corroded.

The solution is to remove the AA battery holder an replace with a CR2032 lithium holder & battery. This is relatively minor surgery. Now my Defender keeps it's s/w configuration settings and high scores. I've read some postings on the net that claim the lithium battery will be drained pretty quickly. I don't know why this would be the case. the CMOS 5101 RAM has a standby current of about 5 uA, this is probably not a whole lot more than the self-discharge rate of the lithium battery. Looking at the schematic I can't see where else there might be a current loss. I figure the battery will keep high scores for about the same amount of time as the shelf life of the CR2032, which is probably 10-15 years.

The speaker for the Defender is ripped and I have to figure out what to do, re-cone this speaker, send it out for re-coning, or just get a replacement. I can get a new speaker for about $21, but re-coning will cost at least $40. But then again a re-coned speaker is more "original".

I started filling the in the dents and holes in the cabinet. I'm staying away from any work that will commit me to totally refinishing the cabinet as I haven't decided if I want to go that far, the side art isn't in bad shape, but there are spots where it's been painted over in a poor attempt to hide scratches.

Defender lives

I got the bridge rectifier from Bob and installed it. The +5 came up immediately. I completed connecting all the components on my work table and fired up the game. No sound, but I got a "rug pattern" on the GO7 monitor. Since this game used to work I suspected that when the power supply went on the fritz it took something with it.

The most likely suspect were the 4116 DRAMs. These were a pretty standard part "back in the day". What's annoying about these parts is they require 3 voltages to operation, a +5, -5 and +12v supply. I also recall (from back when I had a TRS-80 that used these same memory chips) that these chips were finicky regarding how the power is supplied. My guess was when the +5 went out it took the RAM chips down too.

Luckily you can still get these chips, so I ordered a complete set (24, for 48K of RAM) from Bob Roberts. They came in today. I pulled all the old chips and put in the new. I turned the system on and Defender came up.

I'm not playing the game yet I still have a couple of issues to address. I need a new speaker, the one in the game has a rather large tear, though it still sounds good. The bigger problem is I need to fix the battery backup on the game. This is a common problem, when batteries leak their acid tends to corrode the board and eventually the battery holder and traces are eaten away. That's the case for my board so I have some work ahead of me to clean this up.

Battery backup for a Defender game is important, it's not just about the high score. Defender and other Williams games use software configuration. In other words the configuration of the machine is stored in memory (RAM), and if that memory isn't backed up by battery it will "lose" the configuration and the game will be unplayable until it's re-configured. This is a major pain in the ass to perform every time you want to play a game.

So the solution is to either fix the battery holder (AA type batteries), replace with a Bob Roberts replacement (Lithium battery) or try to find the SimTek replacement that swaps out the 5101 with an NVRAM - the no battery solution.

For now I need to move on to the cap kit for the GO7 and make decisions about how far I want to take restoration of the cabinet.

On to Defender!

The Ms Pacman is doing very well in its new home (my eldest daughter's bedroom). There was an issue where the colors of the monitor were off, but re-routing the internal power lines cleared up the issue.

My son and I moved the Defender game into the house. I then proceeded to pull all the guts out of the cabinet (it's an upright) and lay them out on a table. I have confirmed there's an issue with the power supply, it appears the 35A bridge rectifier (BR1) is shot so I've ordered a replacement (& some other parts) from Bob Roberts.

The GO7 monitor is filthy so I've spent some time trying to clean it up. I think I need to hault it out to the garage so I can use my air compressor to clean it up.

Yesterday I used a sponge and some soapy water and cleaned the now empty cabinet inside & out. There's some repair work needed on the cabinet, the previous owner had installed a standard light switch (the kind you have in your home) and cut a rather large hole in the cabinet. After these repairs are done I'm considering purchasing a set of stencils (www.gamestencils.com) and repainting the exterior.

The priority is the electronics. With the parts I ordered from Bob I should be able to get the power supply working. Once the game is operational, I'll re-cap the GO7. Then I can move on to the aesthetics of the game.