[Coco] Issues with 26-3022 interface

[Gene Heskett]

On Monday 11 February 2013 22:40:50 Daniel Campos did opine:

> Hello,
> 
> I just acquired from ebay a 26-3022Tandy interface, but I'm having a bad
> time to make it work with a DSDD drive that I just extracted from my
> CP500 (TRS-80 model III brazilian clone). For what I know, the drives
> from CP500 have the same configurations as a TRS-80 original drive. The
> drive work like a charm on the CP500.
> I made a brief movie showing the error and the functioning of the drive
> (my apologies, but the movie is in portuguese).
> 
> http://www.youtube.com/watch?v=oeiCJYa3jic
> 
> Any hints on what I need to look at on a TRS-80 drive to work with the
> Coco ?
> 
> Just out of curiosity I tested a 5 1/4 HD (1.2M) Drive from an old PC
> and I could make a DSKINI (even with an IO ERROR at the end) and also a
> SAVE and a LOAD on a BASIC program, so it appears that the interface is
> working as it should.
> 
> I also take note on several sites that a mod for HD drives is around for
> this interface. Anyone knows where to find a documentation of this mod ?
> 
> Thanks!
> Daniel

What jumper is set for that drives address?  Where you have it, on that 
"PC" cable, it should be set with ds1 jumpered, and you should have had to 
type DSKINI1.

The end of that cable is twisted, so that the drive plugged into the end of 
the cable is also set as drive 1.  But the cable twist makes it drive 0.

For coco drives, I generally reset the address jumpers so the drives are 
addressed in sequence, starting with drive0=ds0 jumpered, and replace the 
cable with a straight thru cable, replacing any plugs on the cable that 
have missing teeth in the sockets.

So your use of DSKINI0, means that drive is properly jumpered I believe.

The next thing is that there needs to be terminations, in the last drive on 
the end of the cable /only/, and you will have all sorts of I/O errors if 
there are none.  They /must/ be on the end of the cable too else the cables 
signals will have edge ringing from the unterminated stub I see sticking 
out.  So if that drive has 1 or more empty minidip sockets adjacent to the 
edge connector, you are missing those terminations.  The best source for 
those is probably another old drive.

Specifically, what is the model number of that drive?  So-called 1.2 meg PC 
drives turn at 360 rpms, but the coco controllers are all timed for 300 rpm 
drives. I just listened to the DSKINI again, and its too slow, indicating 
it may be a 360 rpm drive and is therefore missing every other index pulse.

I also noticed on the 2nd playback that the head assembly is /not/ moving, 
which it should be a small amount inward with every click you can hear, 
then sweep back out as it starts the verify run.  Can you move it by hand 
when the power is off?

At its age, the grease on the heads slide rails could have turned into 
glue, so you'll likely have to grab a can of denatured alcohol, and a 
carton of cotton swabs on sticks, getting it brand new clean and then 
giving the rods a coat of light oil, similar to sewing machine oil.  Move 
the head in and out to get access to the whole guide rod length.

If you have a product called 3in1 oil, thats quite usable.  The spray lubes 
aren't.  They get all over places they shouldn't, and they dry to a wax, 
not an oil film.  Works great for a day, maybe 2, & then stuck again.

And what happens if you push it toward the middle of the disk, power it up, 
and do a dir0?  It should sweep the head back to the outer, track 0 
position, and hammer the stop for a second or so since the coco ignores the 
drives track0 sensor, then step to the middle of the disk to read the 
directory on track 17.

If it doesn't do as described, start by ditching that cable in favor of a 
straight thru, all teeth present in all 3 connectors version.  I am 
thinking the control signals from the coco are getting scrambled by that 
'PC' cable.

Please advise the list what you found when you did the exercises above.

Cheers, Gene
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