personal history of personal computers

[dwight]

I believe I describe this. There is a nylon clip that holds the guide rail for the head assembly. This nylon was over stressed. Every machine that I've seen, the nylon had hardened and cracked. It allows the rail to float. What happens is that the rail lifts up. When ejecting the floppy the plastic cover catches on the head. One that is removing the disk is likely to assume that it is just the eject hanging a little and they pull the disk out. This rips the head from the mount, destroying the drive.
I saw a Cat on ebay and asked the seller to pass on my email to the buyer, to tell him to not force the disk from the drive, because it would damage the head. I did not get to him soon enough. He had already damaged the head. He said he'd wish he'd read my message earlier.
This is such a common failure that I continue to warn people about it as often as I can. I also did some repair for a fellow that used Cats in his business. I was only able to fix 2 of 5 drives. Luckily these had a head mount was just bent and not ripped off.
The desired fix is to open the disk drive and replace the nylon piece with something to hold it in place. I used a piece of plastic but several use a small dab of JB Weld. There is little reason to ever remove the rail.
The drive use is driven through a soldered on ribbon cable, unlike most such HD drives. Because of software, it requires the DriveReady signal. Most drives no longer have this. It can be created with the retriggerable oneshot, on an adapter cable.
I hope that covers it. Disassembly of the drive is a little trick to get at the rail but anyone with some mechanical ability can do it. Do look at how the eject works before disassembling.
Dwight


________________________________
From: Chris Hanson <cmhanson at eschatologist.net>
Sent: Sunday, January 24, 2021 3:13 PM
To: dwight <dkelvey at hotmail.com>; General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Cc: Fred Cisin <cisin at xenosoft.com>
Subject: Re: personal history of personal computers

On Jan 4, 2021, at 1:31 PM, dwight via cctalk <cctalk at classiccmp.org> wrote:
>
> There was a little known 68K machine. It was the Canon Cat. Although, it was generally not intended as a development machine, in its short life, several applications were developed.
> It was primarily sold as a word processor ( quite powerful one at that ). It had Forth running under the word processor. One could do both assembly and other things once one understood how to access the Forth.
> If you should ever get one, don't use the disk drive until you talk to me.
> It has a common problem that if you don't understand it will destroy the drive.

What happens if it's not possible to talk to you? Can you write up just what the deal is with the drive, so that everyone can learn?

  -- Chris