Upgrading the Amdek Color II

By Ted Felix

June 29, 1982, I got my first IBM PC. In fact it was the first IBM PC. 64kb of memory on the motherboard, two 160kb floppy drives, a cassette interface(!). Those were the days. We got on IBM employee discount since my Dad worked for IBM.

We originally placed the order October 19, 1981. IBM ran a "lottery" to decide on what date during the next year your PC would ship. Our date was a full 8 months after we sent in our order. The moment it arrived, we drove down to ComputerLand to pick it up. I remember we had to get a copy of DOS 1.05 on a Verbatim blank floppy from the guys at ComputerLand because there was some horrible fatal flaw in DOS 1.00. At the time, the only reasonably priced third-party option for an RGB color monitor to go with your Color Graphics Adapter was the Amdek Color II. We bought one of those as well.

When I got it home, I was somewhat shocked. Although BASICA claimed to be able to do 16 colors in text mode, I could only get 8 colors on the Amdek Color II. Soon after, I discovered there was an upgrade for the Amdek Color II that claimed to allow it to display the 16 IBM colors. Since this was long before the internet, I can only imagine that I found out about this either by word of mouth, or from one of the many computer magazines of the time. We had subscriptions to Creative Computing, PC Magazine, and PC World. We ordered the upgrade.

What I didn't realize about this upgrade at the time was that it was totally unnecessary. It turned out that the Amdek Color II was already capable of displaying 16 colors, but they weren't IBM's "official" 16 colors. Dark yellow on the Amdek was just that, dark yellow. On IBM's monitor, dark yellow was brown. The Amdek II color upgrade gave you those "official" IBM colors. To access the Amdek's native 16 colors, all you needed was to upgrade your monitor cable, which I did with an extra piece of telephone wire.

The Amdek color upgrade arrived some time later. I figured I'd go ahead and install it. What follows brings to mind the old adage: "If it ain't broke, don't fix it."

The upgrade required some soldering to install, and since I was already a whiz with the soldering iron at age 14, I figured it wouldn't be a problem. So I dug in. Unfortunately, at some point while testing the upgrade, I accidentally dropped a loose wire (that was connected to the upgrade) onto the monitor's main printed circuit board while the power was on. There was a loud *crack* and a flash of light. Needless to say, the damage had been done. I looked at the monitor, and the image was flipping around like mad. I believe we paid somewhere in the neighborhood of $500 for that monitor. No small sum in 1982.

We decided to try taking it to a TV repair shop. The shop said they should be able to fix it. After all, it's just a TV without the RF section. We also gave them the computer so they would have a signal generator to work with. They figured out which parts were likely to have been damaged and called Amdek to order them. Amdek told them that since they weren't an "Authorized Repair Center" they couldn't send them the parts. So the TV repair shop returned the monitor and computer to us and apologized for not being able to repair it. Fortunately, they left the list of parts that needed replacing attached to the monitor.

I got on the phone to Amdek and found that although they won't sell parts to an unauthorized repair center, they will indeed sell parts to an idiot kid who just fried his monitor. The parts (two ICs) arrived, and I (carefully this time) desoldered the old ICs, installed sockets and installed the new ICs. Then I hooked everything up. Time for the smoke test. While the display wasn't flipping by quite as quickly as before, it was still completely unstable. I figured this was now beyond me, and we decided to ship the monitor back to Amdek for repairs.

It cost about $13 to ship the monitor via UPS back to Amdek. Two weeks later the monitor arrived on our doorstep. No note from Amdek, nothing. I plugged it in, and it still didn't work. Now I had a sneaking suspicion that the monitor was actually working fine, and the computer was at fault. On this hunch we visited a fellow IBMer who also had a PC with a CGA card and tried hooking it up there. Sure enough, it worked perfectly.

Now I knew the problem was with my PC. So, I pulled out my handy dandy IBM Technical Reference Manual for the PC and flipped to the Color Graphics Adapter schematics. I figured that the dropped wire had sent a surge of high voltage back through the CGA adapter, frying some component on the way. I followed the lines from the monitor connector back to the first semiconductor and it turned out to be a single integrated circuit that drove all of the lines to the monitor. That had to be it.

I obtained a replacement IC, removed the old IC, installed a socket, and installed the new IC. Then I hooked everything up, and it all worked perfectly. I decided at this point to leave well enough alone, and I stored the 16-color upgrade away on a shelf.

All told, I think I spent less than $50 to fix the horrible mistake I had made with this $3100 PC and monitor. Not bad for a 14-year-old kid.

The Instructions

Click to read...

The Board

Click for a closer look...

Note the SN74LS86N 4-channel, 2-input XOR gate and the N82S153N 18×42×10 Field Programmable Logic Array with a whopping 8 inputs + 10 bidi I/O lines, 42 and-gates, and 10 or-gates! Those really were the days.

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Disclaimers: This is a wild tale of my life growing up during the PC revolution. I am not affiliated with any of the companies mentioned in this page in any way other than as a customer. All trademarks are owned by their respective owners. There are no ads on this page, and there never will be. Use this information at your own risk. I won't be held responsible for anything that happens to you as a result of reading this. Shake well before serving. The contents of this page are Copyright 2002-2022, with all rights reserved by me, Ted Felix.