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doubledown

Coleco ADAM Ram Expansion and Tape Drive Repair

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Well since finishing the Mini ColecoVision, I thought I'd get to a few new mods I wanted to try with the Coleco ADAM. I found a website that is hosting all the issues of a magazine called "Expandable Computer News" which was published from 1984-1988. Its all about computers and video games from back in the day and it specializes in the ADAM. I found an article in the September/October 1987 titled "Expand Your Memory." It details how to add 64K of memory by installing individual RAM chips versus buying a Memory Expander card. The writer explains that this mod could be done for a bit cheaper than buying an actual Memory Expansion board back in 1987. Since these Memory Expansion cards aren't readily available any more, and when they do pop up on Ebay, they don't sell for very cheap, I thought I'd give it a try. Eight RAM chips need to be piggybacked with the existing chips and a wire to connect pins 15 from each new chip to a point on the board. Here's a few pics with it working:

 

Here's AdamCalc loaded with the 64K upgrade icon displayed:

 

64kramscreeneb7.jpg

 

Here's a pic of the console with no Memory Expansion card installed. It would be inserted in to the slot on the far right, slot 3:

 

64kramslothz6.jpg

 

Here's a link to the article for anybody who wants to give it a whirl. This link should put the article at the top of your screen, but if not, its the 4th article down:

 

http://www.sacnews.net/adamcomputer/22.html#ECN22-4

 

For what it's worth I got my RAM chips in a lot of (9) on ebay for under $10.00 shipped.

Edited by doubledown
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That seems like one hell of an easy upgrade. A tougher thing would be for me to come up with a decent reason to actually do the upgrade though. :D

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That seems like one hell of an easy upgrade. A tougher thing would be for me to come up with a decent reason to actually do the upgrade though. :D

 

I agree, I don't have any Adam software that requries the extra RAM, but what the hell. I just wanted to see if I could do it I guess.

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"Do you desire AdamCalc's on-line HELP feature ?"

 

Wow, that's pretty formal. :P

 

 

I think most would have gone with "Do you want on-line help?" or "On-line help? (Y/N)". :)

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I've heard more than a few people talk about having a Digital Data Drive that will run a tape all the way to the end, then start making a clunking noise, while never loading a program. The case for most is that the little rubber pinch roller wheel is missing. The aluminum hub is still present and spinnable, but the rubber outter wheel is gone. I've got one of these problemed drives myself so I thought since it already doesn't work, I'm not too afraid of screwing it up. On a starndard audio cassette deck this pinch roller is nothing more than a spinning wheel which the tape rides on. In the ADAM drives, this wheel is actually an encoder within the housing. Much like how the Steering Wheel Module and Roller Controller turn the pulses from a sloted disc into on-screen motion, this slotted disc must somehow use the pulses it counts to control where the tape starts and stops and the likes. So if there is no rubber wheel present for the moving tape to make contact with, which in turn would spin the encoder disc, the ADAM has no idea how far the tape has reeled and that's why it runs to the end. I measured the ID and OD of the rubber wheel on one of my good drives and I've got some replacement material on the way. With any luck this will be a fix for all of those non-functioning Digital Data Drives you've all got lying around.

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I got the new rubber in today and got it fitted onto the drive's pinch wheel / encoder shaft. Seems like a real good fit, just a little smaller than the hub its pressed onto so it pretty much stays in place by itself, but I added a few small drops of super glue just in case. It looked like the original wheel had some adhesive to hold it onto the hub too. I got the drive re-assembled and I'll test it tonight when I get home, but I'm very optimistic! :cool:

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All right... for any of you who have an ADAM tape drive with the problem listed above, here's your fix. The only part you'll need is some rubber tubing that is 3/8" ID, and 1/2" OD. I used Viton as it will last a little longer than Buna or Latex, but it is definately a little harder than the original (seems to work just fine in mine). Once you have your tubing (I got mine from McMaster Carr, I use them a lot for work) slice a bit off, 11/64" in length. Take apart your tape drive from the back. First the rear case (cord grip, and 4 screws). Then the outer RF shield and printed circuit boards (3-4 screws) and inner RF shield. On the bottom inside of the drive below the motors is a small square cover with 2 screws. Remove the screws, gently lift the cover slightly, and slide out the opto sensor (has 4 wires going into it). With the opto sensor pulled out, take the square cover off. Be cautious as there are 2 real small parts in here. One is a very small bushing (looks like a tiny silver washer), the other is a small axle (looks like a very small pin) that the encoder shaft spins on. Once these are removed, pull the encoder shaft and be careful with the encoder's disc. It is attached to the shaft, but is very thin and fairly delicate. Put 2-4 small drops of super glue onto the hub and slide the rubber tubing onto it so that the rear face is flush with the rear face of the hub. Once the glue is set, trim the front of the rubber if it sticks out farther than the front of the hub, by using a razor blade flat against the hub's face. Once done, re-assemble in the reverse order, minding the wiring routing so none get pinched, and bingo... a working tape drive. Such a simple fix.

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On a starndard audio cassette deck this pinch roller is nothing more than a spinning wheel which the tape rides on.

Just for the sake of technical correctness....

 

It pinches the tape against the capstan, which controls the speed of the tape movement. Without it, the tape will run too fast & inconsistantly because it's only being driven by the spring loaded slip drive that drives the tape reels.

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Agreed. Thought I'd simplify for the sake of less words to type and my expertise in audio/data cassette decks is limited to my recent online research the other day! :D

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Ah, glad I came across this thread again. I read it the first time, but now I actually have an Adam - and it is having this exact problem! (Sold to me as "working just fine"... pfft. Oh well - as long as I can get it up and running)

 

EDIT: Also, does anybody have a picture of what the tape drive SHOULD look like? I don't see anything inside of mine that looks like it is missing any rubber... (and there isn't any rubber pinch wheel that I can see)

Edited by Atariman

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Ill check when I get home. We can fix it.

 

AX

 

Sweet :) Yeah, I'm pretty confident that it's fixable as the system itself is in pretty good condition (most of it just needs a good cleaning, but the keyboard is yellowed enough that making it look really nice is unlikely) and doesn't look like it was used a ton or abused.

 

I can't wait to play some Buck Rogers on it :)

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If someone tries this, try Super Dambusters and see if it goes past the title screen. We're trying to see if it plays with the extra memory.

 

Tempest

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@ Atariman: If you open the door to the drive, you will see the magnetic read/write head as a shiny silver block on the bottom in the dead center. To the right of that will either be a black rubber wheel, or a shiny silver wheel. If the wheel is silver, than the rubber is gone and that's what causing your problem. If the rubber wheel is intact, use your finger to verify that it spins smoothly and very freely for several rotations. But if you're having the problem where it spins the entire tape to one spool, than you get the click, click, click sounds, I'd assume the rubber is gone.

 

@ Tempest: I think the recent attention to this thread is about the DDD repair not the memory upgrade.

Edited by doubledown

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@ Atariman: If you open the door to the drive, you will see the magnetic read/write head as a shiny silver block on the bottom in the dead center. To the right of that will either be a black rubber wheel, or a shiny silver wheel. If the wheel is silver, than the rubber is gone and that's what causing your problem. If the rubber wheel is intact, use your finger to verify that it spins smoothly and very freely for several rotations. But if you're having the problem where it spins the entire tape to one spool, than you get the click, click, click sounds, I'd assume the rubber is gone.

 

Uh oh. Yeah, this is what I was afraid of. I see the magnetic head and the little metallic wheel, but the wheel won't budge. It isn't even just sluggish, it's completely jammed. Looks like I may have to disassemble the drive more than I was hoping I'd have to (oh well, I'd have to do this to replace the rubber, anyway)

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The "locked" feeling may be, that a portion of the missing rubber wheel is stuck inside the encoder assembly. Once you take it apart, you should be able to tell for sure. The other possibility is that the shaft is out of one of its sockets, or damaged.

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The "locked" feeling may be, that a portion of the missing rubber wheel is stuck inside the encoder assembly. Once you take it apart, you should be able to tell for sure. The other possibility is that the shaft is out of one of its sockets, or damaged.

 

Yeah, I looked at the shaft the little wheel was attached to and it looked like it had some dried up lubricant on it or something. I took the drive apart (as best I could without desoldering wires) and managed to take the back off of the encoder - nothing but a huge mess that needs to be thoroughly cleaned. I'm not sure what I'm going to use on it, though... might actually have to desolder a thing or two just to get it out...

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I took a little time today to try and get some of the "gunk" out of the encoder - I actually had to peel the two, thin pieces of the encoder apart and was initially just trying to scrape the crud off with my fingernail. Realizing that this wasn't going to clean the two parts very well, I put them in a dish of rubbing alcohol and let them soak.

 

Using a toothbrush, I scrubbed the a little bit and got them both looking pretty clean. I reassembled the encoder (mostly) and it now spins freely (I cleaned the crap out of the encoder housing as well as it was pretty bad).

 

So... does anybody have piece of this rubber that I could buy for a small price, or will I need to purchase it somewhere? Also, does anybody have a close-up of the thin "wheel" at the internal end of the shaft? I want to know if I inadvertantly damaged mine (I see a bunch of tiny notches and one large one - is this right?)

 

Anyway, if anybody has any tubing mentioned in the original post that they'd be willing to part with for a small fee, I'd be happy to not have to search around for it. :)

 

EDIT: Thought it might also be worth mentioning that I cleaned the "eye" of the encoder as well with rubbing alcohol and a Q-tip (figured it wouldn't work very well if the eye itself was cruddy)

Edited by Atariman

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I went ahead and purchased some high performance synthetic rubber tubing that matches the above specs - I'll be sure to post my results! :)

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I'm also having the same problem with my ADAM tape drive. Did anyone find any black greasy tar like substance while they were removing the parts of the tape drive? It would be great if someone could put together a kit with the rubber pieces that are needed for this fix. $$$$$ I would expect that this is going to be a common issue with these systems. I'm also looking for a manual that describes the wiring (color pattern) for the internal connectors on the servo and logic boards. I had one of the connectors fall off and I'm not 100% sure of the positioning where you have the 3 plastic connectors on the circuit board. Did anyone by any chance take any pics or notes as they removed the pieces?

 

 

Thanks for your help.

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I didn't take any pics, but yes, I saw the same goop. It locked up the decoder wheel entirely! Feel free to ask me any questions and I'll do my best to describe how I fixed up my drive. :) I think I stil have some of my rubber tubing left if you need any!

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That would be great. My wheel is locked up as well. Did you by any chance record the color pattern of the connectors on the circuit boards? Shoot me an email to [email protected] and I'll send you over my address if you still have a piece of that rubber tubing. I just got the drive apart and I'm basically at the point where I need to remove the black box with the two small screws. What should I expect when I get into that area? Should I use alcohol to clean the black stuff up?

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