Radio Shack TRS-80 Color Computer 2 Teardown

[@turgin9098]

My first computer was also a 16K CoCo2. I was in the 8th grade and two of my friends had gotten CoCo2's from their parents. They came to school talking about them and I was jealous so I begged my dad for one for my birthday. I read that BASIC manual over and over and checked out every book I could find in the school library on computers. I finally got a cassette drive several months later and was thrilled I could save and load programs. By the time I was in high school I had written a maze type text based adventure game that allowed saved games and had some crude text "graphics". I was so excited to take the only computer class available at my school but I soon realized I knew more than the teacher. She caught me debugging my game code one day during class and asked me where it came from. When I told her I wrote it and she asked why I was even in the class. I said because its the only one available! Today I am a network engineer and it all started with that birthday present from my dad so long ago. He was killed in a car accident when I was in the 10th grade so never saw what became of it but I credit him for enabling the way I make a living today.

[@supercompooper]

I wrote a popular skiing game for it. Also a drawing program and a few small games. It was my first computer!

[@perfectionbox]

The I/O ports were memory mapped, which was an interesting difference from the x86 CPUs. On the Coco you would read/write a memory location to recieve/send data to a device, using the load/store instructions instead of dedicated in/out instructions.

[@uni-byte]

The "melted" keyboard showed up on the last of the COCO 1s and the first edition of the COCO 2. Most COCO 2s had the same type of keyboard as the COCO 3 - full-travel, full-height keys. However the COCO 3 had a slightly different arrangement and a few extra keys. Yours is actually a fairly rare COCO 2, at least compared to the regular COCO 2..

[@ridiculous_gaming]

I worked for Intertan/Radio Shack Canada in the late 80s.

[@danadams1030]

I had a 64k CoCo 2. Started with the tape drive then upgraded to a disk drive. Saved for it myself...felt like it took for ever. I learned to program basic and a little assembler on it. Was a good start to my career as a developer.

[@johanlaurasia]

There was a game that used the cassette relay to fake a sort of faux morse code for a game (for effect only, it was any actual morse code, it just was an effect for the game).

[@tenminutetokyo2643]

I upgraded my CoCo 1 I bought off eBay broken, and replaced 40 parts at once, but still no dice. Black screen. But all the power parts are working fine.

[@Starchface]

Great video! The page from the Radio Shack catalogue is a nice touch. I must say it's brutal how much Radio Shack was charging for the Extended BASIC ROM. Highway robbery, I tell you. Nice to see the old Coco 2 being taken care of. Looks to be in good condition. According to a service manual which I found on-line, the 555 timer is used in a so-called artifacting circuit. Essentially it is a hack that forces an MC1372 located inside the RF modulator to turn on the NTSC color burst signal in high-resolution (192x256) mode, "contrary to the original design of the component." This produces red and blue in what would otherwise be a black-and-white-only mode. I do not see a similar circuit in the PAL Coco 2. I had a Coco 3 growing up. That was a pretty nice machine, but I did not have a disk drive. My parents made me choose between a printer and a disk drive. I opted for the DMP-130, reasoning that the ability to produce hard-copy output would be very useful (and it was-I used it to print out homework assignments); however, I can tell you that using cassette tapes for storage is a massive headache. The EDTASM assembler, while crude, did the job. With the hybrid 8/16-bit registers and well-designed ISA, the 6809 was light-years ahead of the 6502. It was an absolute joy to program, not that I ever did anything very useful.

[@RetroLogicLaboratory]

Thanks for the great comment! My parents got stuck with the bill for my computer tech, and that stuff was expensive back in the day. I spent my first year or so with a cassette recorder. Ah the dreaded IO ERROR :)

[@smalltownMainer]

i have a coco 2 with the regular height keys. and the power supply is in a cage, so its a later one.

[@rflberg]

The 555 timer does something to the artifact colors. It is explained in detail in the service manual.

[@RetroLogicLaboratory]

Thanks! Yeah looking at the service manual its described in there. 80's engineering; how to double the number of colors without a new graphics chip. :)

[@dmmikerpg]

I have a CoCo 3 laying around the house somewhere.

[@colorcomputerstore457]

About 3 million CoCos (from 1 through 3) were estimated as being sold. But no 'official' numbers. The early 'melted keyboard' are as shown in your video. They are to repairable. Later melted keyboard and then the full-size keys became repairable. The 'cage' around the power supply was to reduce RF noise. Nice video.

[@colorcomputerstore457]

A little off on your description of the RF output. ALL TVs still have a 75 OHM coax connector on the back. That is where you put in your cable TV. It's easy to use a dongle to convert from RCA to 75 OHM. THen put TV to 3 or 4 and you are good to go. Some TVs might require you to 'scan' the antenna signal. So do that if no image. What most people make errors about is thinking that (A) they need the external RF modulator that use to connect to the TV (B) Assume the RF output is composite and try to connect to that... Some times, after connecting the CoCo, you may need to tinker with the internal RF modulator to get the sharpest image.

[@cpace123]

I know this is a little old, but you might know. I have a coco2 that only reports 8k when typing in print memory. I want to add memory. There are several 4116 memory on ebay, but they have different designations. Here is an example. HYB4116P3DH. The chips look right, but I was wondering where to find what the different numbers mean. Any help would be great. Thanks

[@ConnorR.mp3]

later coco 2s had transformer cages

[@renatoamaral2029]

I had a Coco 2 with 64K Ram in the 80s for many years. Then a chip overheated for some reason and I was unable to repair the computer at that time. I regret I threw it to the garbage during the 90s. 😢

[@kenunix1863]

I remember O/S 9. It got me started with Unix type O/S.

[@JeffSmith03]

Well on my CoCo 2 with 16K the power supply is protected in a cage

[@ingmarm8858]

Nice video but you really need some ESD control happening, be a shame to damage these treasures (I also have lots).

[@raymondheath7668]

"No user servicable parts inside" ......Ha!

[@infinitecanadian]

You wouldn’t have to throw the keyboard out if it failed; you could break the welds and then put in self tapping screws.

[@alexabadi7458]

probably in French because it was also sold in Canada

[@renatoamaral2029]

I had a Coco 2 with 64K Ram in the 80s for many years. Then a chip overheated for some reason and I was unable to repair the computer at that time. I regret I threw it to the garbage during the 90s. 😢