15 Jan
2005
15 Jan
'05
1:06 p.m.
-----Original Message-----
From: ard(a)p850ug1.demon.co.uk [mailto:ard@p850ug1.demon.co.uk]
Sent: Saturday, January 15, 2005 9:53 PM
Qume drive
working, but don't know where to go next. I
guess I could swap
the boards between the two units, but that'll
only tell me if it is
electronic or electro-mechanical.
Other than that, any suggestions for figuring out if it is
alignment, broken
sensor, or something electrical?
The alignment adjustments, in general, are what are known as
'interchangeability adjustments'. In other words, if they're
a bit off,
the drive will be able to format, read, and write its own disks, but
those disks will not be useable on other drives, and vice versa.
So what you do first is to hook the drive up as B: and try
formatting a
blank disk in it. Note that if, for some reason, the machine
thinks it
only has one drive, it'll map A: _and_ B: to that drive.
You'll get some
obvious messages if this has happened, in which case the problem is
certainly not just alignment. This sounds like track0 sensor problems. I assume
you've
blown the dust
out of the sensor? If you have a multimeter and logic probe,
I'll dig out
the schematic and tell you what to look for.
Yes, I have blown the dust out of the sensors. See above. How do these
drives signal that they are DS? That seems to be where the error is coming
in. Any tips based on the schematic would be of help. Since all I have at
the moment is a DMM and a homemade logic probe, my tools are lacking to
fully solve this problem.
Thanks again,
Kelly
Kelly
16 Jan
16 Jan
5:56 a.m.
Qume drive working, but don't know where to go
next. I
guess I could swap
the boards between the two units, but that'll
only tell me if it is
electronic or electro-mechanical.
Other than that, any suggestions for figuring out if it is
alignment, broken
sensor, or something electrical?
The alignment adjustments, in general, are what are known as
'interchangeability adjustments'. In other words, if they're
a bit off,
the drive will be able to format, read, and write its own disks, but
those disks will not be useable on other drives, and vice versa.
So what you do first is to hook the drive up as B: and try
formatting a
blank disk in it. Note that if, for some reason, the machine
thinks it
only has one drive, it'll map A: _and_ B: to that drive.
You'll get some
obvious messages if this has happened, in which case the problem is
certainly not just alignment. same diskette put back in the working drive formatted
to 360K. So, how do
these drives tell if they're dealing with SS vs. DS meadia? Does it just
look for a signal from the second head? Is there another sensor that
indicates "yep - double sided". This is how it works with 8" drives. The
index hole is in a physically different spot.
Unlike the 8" drives, there is no signle/double sided signal on the 5.25"
drive interface connector, and there's no sensor for anything like that
(I looked at the schematics this morning, they look pretty standard,
there are 3 sensors for index. write protect, and track 0).
My guess is that either :
a) The side select signal does nothing due to a logic fault in the drive,
and that therefore when it tries to read the second side, it gets the
data from the first side. A true signle-sided drive would do this.
b) There is no useful signal from the side-1 head (this is the head on
the top surface of the disk, of course), either because the head is
dirty/defective, or a damaged connection back to the logic board, or an
electronic fault on the board. I am not sure what the software would do
under those conditions -- by rights it should give errors for every
sector on side-1, but it's possible it then assumes the media is really
single-sided, and formats it accordingly.
I think i will have to grab the schematics and see if I can talk you
through the circuitry.
in. Any tips based on the schematic would be of help.
Since all I have at
the moment is a DMM and a homemade logic probe, my tools are lacking to
fully solve this problem.
Well, although _now_ I have some very nice test gear, I debugged my first
homebrew computer (This was when homebrewing meant soldering chips to
stripboard and wiring everything up, not pluging a video card into a
motherboard) with an anlaogue multimeter and an LED+resitor 'logic
probe'. So it certainly _can_ be done...
-tony
6:59 p.m.
On Sun, 16 Jan 2005, Tony Duell wrote:
> same diskette put back in the working drive
formatted to 360K. So, how do
> these drives tell if they're dealing with SS vs. DS meadia? Does it just
> look for a signal from the second head? Is there another sensor that
> indicates "yep - double sided". This is how it works with 8" drives.
The
> index hole is in a physically different spot.
Why we always sneered at the hateful 5.25's.
The FATID byte is used to know the sidedness on reading; the FAT,
like boot sector, is always on the first side. 160, 180, 320, 360,
make up your mind! :-)
b) There is no useful signal from the side-1 head
(this is the head on
the top surface of the disk, of course),
For all the possibilities you state, likely cause.
Well, although _now_ I have some very nice test gear,
I debugged my first
homebrew computer (This was when homebrewing meant soldering chips to
stripboard and wiring everything up, not pluging a video card into a
motherboard) with an anlaogue multimeter and an LED+resitor 'logic
probe'. So it certainly _can_ be done...
Likewise! On my very first own computer, SWTPC 6800, I debugged
the fact I miswired the (20mA loop) tty using a Tek 555 scope to
ID the Mikbug code loop waiting for the start bit. I was too dumb
to realize I should have checked for Rx into the PIA :-)
Soldered every damn chip and all those molex "card edge"
connectors one at a time. Ugh. Plus a whole tube of 2102's (and
not 21L02's) a year later.
Now I buy only laptops, nearly impossible to even open them, and
quite happy with that. :-) Even having to stick in a PCMCIA card
these days seems invasive. Why isn't that built in?
17 Jan
17 Jan
9:41 a.m.
b) There is no
useful signal from the side-1 head (this is the head on
the top surface of the disk, of course),
For all the possibilities you state, likely cause. Well, although _now_ I have some very nice test
gear, I debugged my first
homebrew computer (This was when homebrewing meant soldering chips to
stripboard and wiring everything up, not pluging a video card into a
motherboard) with an anlaogue multimeter and an LED+resitor 'logic
probe'. So it certainly _can_ be done...
Likewise! On my very first own computer, SWTPC 6800, I debugged
the fact I miswired the (20mA loop) tty using a Tek 555 scope to ID the Mikbug code loop waiting for the start bit. I
was too dumb
to realize I should have checked for Rx into the PIA :-)
Soldered every damn chip and all those molex "card edge"
connectors one at a time. Ugh. Plus a whole tube of 2102's (and
not 21L02's) a year later.
Now I buy only laptops, nearly impossible to even open them, and
Yuck! I'd not want a computer I couldn't easily pull apart, and I'd not
want one without proper expansion (not Useless Serial Botch). Heck, I've
even played about with the processor bus in HP handheld calculators...
quite happy with that. :-) Even having to stick in a
PCMCIA card
these days seems invasive. Why isn't that built in?
The stuff I want is rarely built in, because no sane person would want it...
-tony
18 Jan
18 Jan
11:17 a.m.
On Mon, 17 Jan 2005, Tony Duell wrote:
Sure, _IF_ that would cause the MS-DOS format program to assume the disk
is single-sided.
We're getting into the area where my memory is doing the
remembering and not me, but I believe that with 5.25" diskettes,
you the human tell the formatter, with the appropriate command
line switch, which sidedness you want to use. If you in fact have
SS drives physically installed, you will get a FORMAT ERROR iff
you use /V (note the formal iff).
That advice, plus $3.50, buys you coffee at Starbucks. Easy to
check but I ain't got me no peecee no more.
Oh! No, I did it at work! It wasn't a 555, it was a 564, the
storage job. Sorry for the confusion doubled. I do own a 564 now,
since they are umm let's say heavily discounted today.
My laptop is purely a software machine. In fact, it's purely a
*text* machine; I run freeBSD, everything stored as ASCII, perl
scripts to drive anything complex. Portable from machine to
machine. I have things that are purely hardware too.
b) There is no useful signal from the side-1 head
(this is the head on
the top surface of the disk, of course),
For all the possibilities you state, likely cause. Likewise! On
my very first own computer, SWTPC 6800, I debugged
the fact I miswired the (20mA loop) tty using a Tek 555 scope to
Yo uhad a 555? I managed (then) without a 'scope at all. Now my 555 is
alongside me with a good selection of plug-ins. I don't use it all that
much -- I find a logic analyser to be a more useful instrument, but anyway. Now I buy only
laptops, nearly impossible to even open them, and
Yuck! I'd not want a computer I couldn't easily pull apart, and I'd not
want one without proper expansion (not Useless Serial Botch). Heck, I've
even played about with the processor bus in HP handheld calculators... The stuff I want is rarely built in, because no sane
person would want it...
Sane people? Who needs them? From them we get malls, fast food
insurance forms, and warfare.
19 Jan
19 Jan
9:42 a.m.
Yo uhad a 555?
I managed (then) without a 'scope at all. Now my 555 is
alongside me with a good selection of plug-ins. I don't use it all that
much -- I find a logic analyser to be a more useful instrument, but anyway.
Oh! No, I did it at work! It wasn't a 555, it was a 564, the
storage job. Sorry for the confusion doubled. I do own a 564 now,
since they are umm let's say heavily discounted today. Yuck! I'd
not want a computer I couldn't easily pull apart, and I'd not
want one without proper expansion (not Useless Serial Botch). Heck, I've
even played about with the processor bus in HP handheld calculators...
My laptop is purely a software machine. In fact, it's purely a
*text* machine; I run freeBSD, everything stored as ASCII, perl scripts to drive anything complex. Portable from
machine to
machine. I have things that are purely hardware too.
Oh, I certainly agree with you there :-)
-tony
The stuff I want is rarely built in, because no
sane person would want it...
Sane people? Who needs them? From them we get malls, fast food
insurance forms, and warfare.
16 Jan
16 Jan
9:14 a.m.
Well, I did this and learned something VERY important.
The disk only
formatted as 180K. So, it doesn't see that it is a double sided drive. The
same diskette put back in the working drive formatted to 360K. So, how do
these drives tell if they're dealing with SS vs. DS meadia? Does it just
look for a signal from the second head? Is there another sensor that
indicates "yep - double sided". This is how it works with 8" drives. The
index hole is in a physically different spot.
I've got the schematic in front of me. The head selection circuitry is
quite qimple, and the rest of the read/write chain is common to both
heads, so presumably it's working correctly.
The heads are selected by U4 (75451 dual AND gate/driver), the outputs of
which are pulled to+5V, and slo drive the bases of Q7 (Head 1) and Q6
(Head 0), PN2222 transistors via restors. One input of each of the AND
gates comes from the power-OK circuit, built round Q9 and Q10 (as this is
common to both heads, it's working correctly), the other input comes from
the sides select signal on the connector (U4b, for head 1) or from that
signal inverted by U8b (7414) on U4a, for head 0. That should give you
some components to check.
As normal, the head switching involves diodes, in this case CR1-CR3 for
head 0 and CR4-CR6 for head 1. The heads plug into the connectors A1-A7
(Head 0) and B1-B7 (Head 1), the pinout being :
1,2 : ground
3 : Erase drive
4,6 : Head select (other end of erase coil, centre-tap of read/write coil)
5 : One end of the read/write coil
7 : Other end of the read/write coil.
You can check the head for continuity, but don't pass too much current
through it, and if possible demagnetise it (a tape head demagnetiser is
fine) after measuring it.
-tony
7278
days inactive
7282
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