Re: FD 2000 Teac mechanism

I mean CMD had to physically change some of the electronics on the PCB ON
the Teac mechanism to work with
THEIR PCB they made to be compatible with the 1581 and then the High
Density.
There was a second revision also of the TEAC mechanism so I  used my
original FD-2000 PCB to kind see what CMD had
hacked to make it work properly again with the 1581 and High Density.  One
was the disk change if  you remove a disk and put a new one in it
will sense that, I have that working, its just all the rest I dont know
what changes *Electronically* to make it all work.

Terry Raymond


On Mon, May 31, 2021 at 11:28 PM Roberto Muscedere <rmusced_at_uwindsor.ca>
wrote:

> This kind of sounds like an issue that was in the vice emulator.
>
>
>
> It seems the floppy disk controller has a time out for recalibration on
> the FD-2000. The amount is 77 pulses (or tracks), but of course the disk
> can have 80 tracks. So what would happen was the controller would time out,
> but the ROM code expected it to, and would reissue the recalibrate command.
> The thing is the ROM code expected a particular return value from the disk
> controller on the first failure. I had to hard code this in the vice
> emulator or else the drive would behave like the floppy was removed and
> subsequently all IO to the disk failed. Perhaps the return value is not
> directly derived from the controller itself but also the mechanism in some
> way.
>
> Here is the comment I placed in the code:
>
> /* CMD FD2000's mechanism also sets bit 5 and 6 on recalibration timeout,
> it is hard coded in ROM to check for $71 on result (_at_ $878a) and try again
> */
>
> /* The FD4000 uses 85 pulses, so this shouldn't timeout */
>
> Maybe a good test would be to put the same mechanism in an FD-4000 and see
> if the issue occurs when using high density disks. In that situation the
> timeout would never happen. Of course I’m not sure how it would like that
> drive mechanism as opposed to an extended density one.
>
> Since this problem I stated occurs during recalibration over 77 tracks,
> are the issues happening when the drive is moving between the partition
> table and the beginning of the first partition (like a native one since the
> header and BAM are at the beginning of the disk)? Does it happen if the
> current working partition starts after track 4? I would suggest creating a
> dummy native partition at the beginning of the disk and avoiding it during
> these tests.
>
>
>
> Roberto
>
>
>
> *From:* Terry Raymond <traymond160_at_gmail.com>
> *Sent:* Tuesday, June 01, 2021 12:30 AM
> *To:* cbm-hackers_at_musoftware.de
> *Subject:* FD 2000 Teac mechanism
>
>
>
> Hi concerning the CMD FD-2000 I have one I first bought from CMD
>
> the TEAC mechanism needs some modifications to work properly.
>
> I found the Disk change and that seems to work.
>
> In all I found 3 noticeable changes on the TEAC PCB so I tried this and it
> kind of works
>
> but sometimes it acts like the disk is not even formatted.
>
> I tried the same files on my still working FD-2000 and those same files
> copied fine.
>
>
>
> So has anyone here ever figured out the hacks for this if so could you
> please send me
>
> viewable pictures please.
>
>
>
> Terry Raymond
>
> traymond160_at_gmail.com
>
>
>