26 Oct
2007
26 Oct
'07
7:51 p.m.
Question
I have a CS3 with a PerSci dual 8" internal drive that does not
recognize/respond when a disk is inserted in drive A, but drive B does
respond when a disk is inserted. Drives C and D are empty. The PerSci
dual 8" drive is the model with the one belt/on-board controller shared by
the two drives. When working correctly, the drive has a mechanical lock
that detects the insertion of the disk, engages the read head, and holds
the diskette in place. No latch arm needed. There are 4 buttons on the
front, one for each drive (A,B,C,D) - If you push the corresponding button
and there's a disk in the drive a motor ejects the diskette
automatically. Pretty cool for a 1979 micro.
Do the diskette detect sensors go bad on these?
Next I tried and failed to get a RDOS monitor prompt, although I followed
the dip switch settings as instructed in the manual. The drive controller
has the RDOS ROM.
I did all of the standard things, re-press the IC's, re-seat the cards,
etc. The system is in very nice shape, no corrosion or scratches.
I feel that I have nailed down the problem to being either the drive, the
drive controller, or the terminal. Through a process of elimination I will
attempt to replace each component in question (except the dual drive, I
will probably put in Tandons instead if I can. I have a head start, the
entire system came together in one donation so I was able to record how it
was all cabled together, and I can assume it worked once as-was. Also
included in the lot was Fortran IV and CDOS software. The printer is a
Texas Instruments Omni 800 / 810 RO Terminal. I was told the system cost
$15,000 new in 1979. A pretty sweet personal computer.
PICS: http://www.vintagecomputer.net/cromemco/system_three/
26 Oct
26 Oct
8:10 p.m.
On Friday 26 October 2007 22:51, B. Degnan wrote:
Question
I have a CS3 with a PerSci dual 8" internal drive that does not
recognize/respond when a disk is inserted in drive A, but drive B does
respond when a disk is inserted. Drives C and D are empty. The PerSci
dual 8" drive is the model with the one belt/on-board controller shared by
the two drives. When working correctly, the drive has a mechanical lock
that detects the insertion of the disk, engages the read head, and holds
the diskette in place. No latch arm needed. There are 4 buttons on the
front, one for each drive (A,B,C,D) - If you push the corresponding button
and there's a disk in the drive a motor ejects the diskette
automatically. Pretty cool for a 1979 micro.
Do the diskette detect sensors go bad on these?
I have one of those systems and it also has a problem with that drive. In
fact the problem was persistent enough that the disk that was in it was worn
clear at the track zero location.
I have some data on it here, and it appears that they use incandescent (!)
bulbs for things like index pulse, etc. in those drives. I strongly suspect
that these are related to the problems I'm seeing, but haven't done anything
with it pending me finding some of those rather odd connectors used to supply
power to the drive, as I'd need to make an extension for it to work on the
unit.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
27 Oct
27 Oct
3:28 p.m.
Question
I have a CS3 with a PerSci dual 8" internal drive that does not
recognize/respond when a disk is inserted in drive A, but drive B does
respond when a disk is inserted. Drives C and D are empty. The PerSci
dual 8" drive is the model with the one belt/on-board controller shared by
the two drives. When working correctly, the drive has a mechanical lock
that detects the insertion of the disk, engages the read head, and holds
the diskette in place. No latch arm needed. There are 4 buttons on the
Actually, there is a latch arm which lowers the hub clamping cone as
usual. It's just that it's operated by the same motor that ejects the
disk, so you don't have to do it manually.
front, one for each drive (A,B,C,D) - If you push the
corresponding button
and there's a disk in the drive a motor ejects the diskette
automatically. Pretty cool for a 1979 micro.
IIRC, there was a way to eject disks automatically, probably by using one
of the otherwise unused pins on the interface connector.
Do the diskette detect sensors go bad on these?
Anything can go bad :-(
It's been a long time since I've been inside my Persci drive, but from
what I rememebr there's a lot of circuitry common to the 2 drives. And
since one of your drives is working, it would appear that all that
circuitry must be working too.
IIRC, the disk inserted sensor uses a filampnt lamp as the light source.
Maybe that's failed. In any case this shouldn't be too hard to trace out.
Next I tried and failed to get a RDOS monitor prompt, although I followed
the dip switch settings as instructed in the manual. The drive controller
has the RDOS ROM.
I did all of the standard things, re-press the IC's, re-seat the cards,
etc. The system is in very nice shape, no corrosion or scratches.
I feel that I have nailed down the problem to being either the drive, the
drive controller, or the terminal. Through a process of elimination I will
attempt to replace each component in question (except the dual drive, I
Before you easter-egg the machine (and thus start _that_ flamewar again
:-)). I feel it would be better to do some tests.
My first test would be on the RS232 cable to the terminal. See if the
machine is sending anything. You caouls also try a hardware loopback
connection on the terminal's RS232 port to see if you can get it to echo
characters from its keyboard to the screen.
Then I'd start looking at he signals on the drive cable with a logic
probe, or batter still a logic analyser. See if the machine is selecting
the drive. Check there's a naindex pulse, that the drive is going ready,
that head is been stepped to cylinder 0, and so on. Then see if the read
data line looks sensible.
-tony
6266
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6266
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ard＠p850ug1.demon.co.uk -
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rtellason＠verizon.net