From: mseals@in.net (Michael Seals) Newsgroups: rec.games.video.arcade.collecting Subject: How I put a PC power supply in my arcade cabinet Date: Wed, 19 Mar 1997 20:33:38 GMT Sorry if this posted before, but my previous posts did not show up in deja news. I've since switched news vendors... First I wanted to thank everyone who helped with this question. For everybody elses benefit, here is the information I received and/or learned in order to help me complete the process. Additionally, I am outlining the steps I took to complete the project. Usual disclaimers apply. Hope some of you find this useful. -MTS- "How I replaced the power supply in my new game". The Problem - I got a new game at auction that worked fairly well at the auction (it was COLD inside the building) but once I got it home and cleaned up the next day, the game exhibited lots of strangeness. In particular I was getting intermittant pulsating coin/start lamps, fluctuating brightness on the monitor, random system hangs, the sound system going offline intermittantly etc. The Diagnosis - All the above items deal exclusively with DC power. The marquee lights and the monitor did not appear to be affected. Upon opening the game I discovered that it still had its original power supply (non-switching linear). I figured replacing the DC side of the house was in order. The Old Power Supply - I decided to leave the old power supply installed and run the new power supply concurrently with the old. The main reason for this is that the old switching supply had an isolation transformer built in to it. Based upon my previous readings in this newsgroup, I learned that a isolation transformer is a Good Thing (TM), so wanted to keep it. The New Power Supply - I happened to have a couple of old IBM PC (AT) style power supplies just lying around. Again, based upon previous readings in the newsgroup, I was pretty sure this PS would be an adequate match. See the end of this post for caveats and technical info on IBM power supplies. The Solution Step 1 (Voltages) - First I needed to determine what DC voltages my game needed. Ideally I would have schematics to refer to and this would be fairly easy. Unfortunately I did not. So I got out my digital multimeter and went to work. First I had to determine which wires carried current from the existing power supply to the games motherboard. Fortunately this was fairly easy to figure out - only one set of six wires went between the power supply and the motherboard. I unplugged these wires from the motherboard and routed them outside the cabinet to work on. I then powered up the game and used the digital multimeter to measure the voltages. Of course, the game did not have any 'standard' color codes (no black wires at all) that I am used to and it took a bit of fiddling to determine which pins were the ground. Notice the third assumption (Green = ground) turned out to be correct. Here is the table of voltages depending on which color I assumed was ground: Wire Red Assumed Ground Violet Assumed Ground Green Assumed Ground RED GND +25 V +5.8 V RED GND +25 V +5.8 V GREEN -6.0 V +20 V GND GREEN -6.0 V +20 V GND ORANGE +14 V +40 V +20.2 V VIOLET -26 V GND -20.2 V Notice the third assumption is the only one of four possible configurations that came anywhere near 'standard' voltages. The + and - 20.2 V figures seemed a bit high, but I attributed this to a possibly malfunctioning power supply, or more likely, to the fact that the power supply was not under load. Step 2 Parts - I needed to make sure the equipment I had on hand would meet the requirements. See the end of this article for tech info on IBM power supplies. I determined that a PC power supply would provide more than adequate amperage at that the voltages would match fairly closely. Since the game somewhat worked, I didnt want to do any work that couldnt be 'undone', so a quick trip to Radio Shack procured a few 9 pin nylon male and female connectors. This would allow me to switch back and forth between the two power supplies with a simple unplug/plug. Step 3 Match voltages - I put together a conversion table indicating which wires from the new power supply should be connected to which wires on the old wiring harness: Old Harness New power supply RED +5.8 V +5V RED RED +5.8 V +5V RED GREEN GND GND BLACK GREEN GND GND BLACK ORANGE +20.2V +12V YELLOW VIOLET -20.2V -12V BLUE Step 4 SNIP and Solder - I disconnected the wiring harness running between the old power supply and the motherboard and removed it from the cabinet. I then snipped the wires halfway between the two connectors. I then attached a male plug to the power supply end and a female plug to the motherboard end. I also attached a male plug to the new power supply end. I wasnt confident that the crimp-on connectors that came with the kit were making solid contact, so I whipped out my soldering iron and gave each connector a good solder, Just In Case. I then reconnected the old power supply and tried the game. It still worked. I then disconnected the power, plugged the new power supply into the motherboard and into the wall and tried again. It worked!!!! Step 5 Eliminating cords - Everything worked, but now I had two power cords to run one game - 1 cord to power the PC power supply, the other to power the monitor and marquee (Old power supply). I could have simply cut the AC plug off the PC power supply, soldered the ends to the incomming terminals of the old power supply and somehow found a way to mount the new power supply inside the game (or not bother mounting it, just shove it inside the box and let it flop around). Instead, I decided to make the switching supply the main power supply for the game. The first step was to mount the power supply. To do this I had to get out my jigsaw and cut a larger opening into the game to allow room for the fan to vent and for the PS to mount flushly (enlarging the power cord hole). I then used wood screws to secure the power supply from WITHIN the cabinet (to deter tampering). Next, I removed the cover from my switching power supply (despite the numerous warning stickers warning me not to), then cut the plug off the old power cord. I then soldered the old power cord to the "Monitor Out" power connector on the PC power supply from INSIDE the power supply. Net result: A standard PC power cord (removable to boot!) plugs into the wall with the other end plugged into the new power supply. This power supply then applies DC power to the entire game. The Monitor Out connector iside the PC power supply then powers up the old non-switching power supply (and its isolation transformer) to power the marquee and monitor. Step 6 Remote power switch - The game did not have a remote power switch when I got it. My next mini project will be to wire up a remote power switch on top of the game so I dont have to either plug/unplug the game or open up the back cover to access the existing power supply switch. I guess I can leave this as an exercise for the student :> --------------------------------------------------------------------- A few words about IBM AT Power supplies. An IBM AT compatible power supply should be able to provide enough power at the appropriate voltages to run most arcade video games. A few caveats are in order however. 1) According to John Dvorak in his book _upgrading & reparing pc's_ old style PC switching power supplies would self destruct if run without a load. Therefore, you should not 'bench test' a PC power supply without running it under load. I pulled my spare PC PS's from working 286's so I assumed they were still in working order. 2) PC power supplies take up some room in the cabinet and require a modification to the cabinet or some creative mounting to install in the machine. IBM AT power supply tech info. A 'typical' IBM AT compatible power supply (read MY power supplies) has the following characteristics: Current 6.2 A @ 115V 3.1 A @ 230V DC Output +5 V @ 23A +12 V @ 9A -5V @ .5A -12V @ .5A Connector Pin outs P9 (motherboard) +5 V - Red Wire +5 V - Red Wire +5 V - Red Wire -5 V - White Wire GND - Black Wire GND - Black Wire P8 (motherboard) GND - Black Wire GND - Black Wire -12V - Blue Wire +12V - Yellow Wire +5V - Red Wire PG - Orange Wire Note: Power Good is a signal sent to the PC indicating everything is OK It is not required for this application. Drive connectors - Just to be complete. +12V - Yellow Wire GND - Black Wire GND - Black Wire +5V - Red Wire