6 Mar
2002
6 Mar
'02
2:44 p.m.
After I inadverently sent mail to the group instead of you personally, I
was scrolling through something unrelated in the archives of this group, and
ran across this link
http://www.classiccmp.org/mail-archive/classiccmp/1999-03/2078.html that
mentioned a FD55-FB (sometimes I wish Google could be told to ignore certain
punctuation). I tried jumpering 'SM', and voila! A good solid head load!
Neither drive had this jumper installed. I think the only reason the drive
ever booted was because the heads don't unload very hard. Weak spring in
the unload mechanism possibly. I dunno. At any rate, the both drives work
perfectly well. I copied some diskettes back and forth a few times, and a
10th generation copy still verifies.
I haven't checked out the second Otrona I have yet, but I suspect it may be
the same problem. Someone swapped these drives out, and they appeared to
work. How reliably, who can say?
The other think I found was that I had 4 screws left over, and damned if I
could figure out where they went. After completely reassembling the unit, I
found I had forgot to put the sheild plate over the lower floppy. This
"protects" the drive electronics from the motherboard. I can say that it's
absolutely necessary on this machine. I thought the second drive was
flakey, since a 2nd generation copy failed to verify several times. Found
the plate behind a box of diskettes, replaced it, and the diskette was
working as a 10th generation copy.
So at least one happy little Otrona, although the keyboard tends to bounce
a little. Perhaps some usage will clear that up. Tomorrow, I check out the
second one (I *really* like these little machines).
Thanks to everyone who offered to give or sell me a 360K drive. I may yet
need one for the other machine, but I have a feel that it'll be fine. Also,
thanks to everyone else that offered suggestions about the drives, etc.
--John
-----Original Message-----
From: owner-classiccmp(a)classiccmp.org
[mailto:owner-classiccmp@classiccmp.org]On Behalf Of Tony Duell
Sent: Wednesday, March 06, 2002 21:37 PM
To: classiccmp(a)classiccmp.org
Subject: Re: Teac FD-55B Floppy Oddity
Tony,
I'm probing around on the PCB, and here's what I find. Pin
42 is
staying
low, no matter what. Shorting pin 41 to ground
causes the head
to load with
I am puzzled... If pin 42 is alwys low, then there's no way the head can
ever load (U8 a would be turned off, so the output will be floating, so
no return path for the load solenoid).
a nice solid thunk. I'm starting to wonder
if the drive *is*
(or ever was)
jumpered correctly. I have HM jumpered (on the
block with
DS0/DS1, etc),
So am I...
and MX (on that same block). Also jumpered is
'PM', off by
itself. There
are no jumpers on the 2x8 block, which contains
labels such as
'UR', 'ML',
'HL', 'SM', 'UO', and
'RE'. There seems to be one other label
on that block
that the silkscreen smeared on, and I can't
read.
If this jumpering sounds reasonable (head load on motor
start is what I
think I want), can you tell me the signal path
from the 'HM' jumper to
wherever it goes?
It's a bit odd, and as far as I can see (it's getting late, so I might be
missing something), the jumper config you have can't work.
The motor-on line (pin 16) goes to one side of the HM jumper. The select
line (common of DS0, DS1, DS2, etc) goes to one side of the HS jumper
(head load on select, I think). The other sides of those 2 jumpers are
linked. Makes sesne so far, we'd want this signal to load the head.
Invert that with U3f (it's now an active high signal). We'll call this
'H' for the moment.
Take motor_on again (straight from pin 16). AND it (remeber it's active
low, so it's really an OR) (U2d) with one side of the ML jumper (also
puled high by a resistor). ML is not fitted, so the output of UD2 is
essentially motor on. Now invert that with U3d. Call this 'M'.
Now AND H and M with U2b. So far so good. The only problem is that the
output of U2b goes to the SM jumper and nowhere else. The other side of
the SM jumper is pulled down (47K resistor in RA4), then goes to pin 40
(HSM) of the 1922-00 ASIC. So without the SM jumper fitted, it can't do a
darn thing.
My schematic has the HM, IU (pin 4 is In Use, not Head Load (which is
what you get idf the HL jumper is fitted instead)) and SM jumpers drawn
it. Might be worth fitting at least SM and seeing what happens.
-tony