Coleco ADAM tape drive encoder wheel

[falter]

Hey guys.

Started organizing my stuff this weekend and came across my ADAM, which had not seen attempted use in over 3 years. I got it off the 'free bench' down at the local computer store. Basically it had a situation where the tape drive would just run endlessly in one direction.

Apparently these units suffered from an issue where what's called an 'encoder wheel' in the high speed tape drive would get gummed up with melted rubber. A drive wheel attached to a shaft that also was attached to the encoder wheel apparently could get so hot it would melt and thus cause the wheel to stick. Since the tape drive doesn't know where it is, it simply keeps going in one direction.

I know this because I stumbled upon a video on youtube here: http://www.youtube.com/watch?v=py5Y1PYUadY That guy is my hero. However like most of those videos some little items are skipped and I was wondering if any of you had advice. The 'gum' on the encoder wheel is quite thick. The video suggested using a solvent, but you never see the actual work going on. Also the encoder wheel's outer edge (the part that is sensed by the drive) is very flimsy plastic or metal. Very easy to break one of the fins. So I'm a bit nervous about scraping at it. Thus hoping there is a solvent that'll do the job. Any thoughts on solvents that would go after melted rubber but not eat the rest of the part?

 

[falter]

Well, I completed the repair and the ADAM's tape drive is functional again! Used acetone to break down the melted rubber, and then gently 'fingernailed' it off. Bought a $5.00 car at a toy store, took one of the tires off, and put it on the wheel at the other end of the encoder wheel shaft, as in the video. Put everything back together and boom... data packs load perfectly.

One question though -- I'm using a composite monitor with it -- which works fine, except no sound... does anyone know how ADAM users with comp monitors dealt with sound? I'm pretty sure this goes through the TV/RF port for TV users... didn't think sound was generated in the actual computer itself... thoughts? I've been digging for a manual but haven't found anything that touches on the subject.

 

[Bungo Pony]

That's a really awesome fix! I'll keep that in mind since I want to eventually get another Adam.

Not sure how you'd get sound with that monitor. I know the RCA jack at the back plugs into one of those RF boxes that connects to the television, and sound comes through the TV speaker.

 

[Cloudscout]

There are two RCA connectors and one DIN connector on the back. The first RCA connector is the RF out which will deliver both picture and sound to a connected TV. The second RCA connector is composite video out which, obviously, only delivers the picture. The DIN connector will give you both composite video and audio out, however, you need the correct cable. I was hoping that a Commodore or old Sega Genesis cable would have a compatible pinout but they don't. You could make one yourself, though, without too much trouble. I'm actually going to be making one for myself this weekend. The pinout is here:

http://www.theadamresource.com/schematics/ADAM-video-pinout.jpg