31 Oct
2009
31 Oct
'09
6:49 a.m.
I just purchased one of these on ebay, but am unable to find even a shred
of documentation on the web.
It's equipped with a "PC" style 4-pin Molex connector for power, unlike
the more usual 6-pin square connector used by all my other 8" drives.
What I'd like to confirm is whether this unit can actually run on 12VDC.
It does not seem to work correctly with 12V applied, which could suggest
either that it requires 24V or is defective.
Before I let the magic smoke out of it, does anyone know the proper
voltages for this drive?
Steve
--
31 Oct
31 Oct
4:38 p.m.
Before having applied power, you might have wanted to look up some
components and buzzed which of the pins that the power pins went to, or
looked at any voltage conversion tanks for clues to the supply in and
outputs before applying power in any way. It might just be that Molex
had cheap connectors that week, and you fried the thing completely
(sorry to be down, but it is a common connector)
Hopefully it is just that it needs the extra voltage. Weren't some of
the 8" drives triple voltage? it might have 5, 12, and 24 on 4 pins as
another guess.
Jim
Steven Hirsch wrote:
I just purchased one of these on ebay, but am unable
to find even a
shred of documentation on the web.
It's equipped with a "PC" style 4-pin Molex connector for power,
unlike the more usual 6-pin square connector used by all my other 8"
drives. What I'd like to confirm is whether this unit can actually run
on 12VDC. It does not seem to work correctly with 12V applied, which
could suggest either that it requires 24V or is defective.
Before I let the magic smoke out of it, does anyone know the proper
voltages for this drive?
Steve
1 Nov
1 Nov
5:36 a.m.
On Sat, 31 Oct 2009, jim s wrote:
Before having applied power, you might have wanted to
look up some components
and buzzed which of the pins that the power pins went to, or looked at any
voltage conversion tanks for clues to the supply in and outputs before
applying power in any way. It might just be that Molex had cheap connectors
that week, and you fried the thing completely (sorry to be down, but it is a
common connector)
Not likely that I fried it. It goes through the motions of working: motor
spins, head-load solenoid tries to engage. Stepper steps (although a bit
haltingly).
This unit is WAY too recent to be a three-voltage drive. It's the most
contemporary 8" drive design I've ever seen, in fact. That's why I
thought it was at least plausible that it ran on 12V!
I'm going to go for it and try a higher voltage. There's no reason that a
12V regulator would be hung off the input - through a 100-ohm, 5W resistor
- unless there was supposed to be > 12V applied.
Steve
--
31 Oct
31 Oct
6:03 p.m.
On Sat, 31 Oct 2009, Steven Hirsch wrote:
I just purchased one of these on ebay, but am unable
to find even a shred of
documentation on the web.
It's equipped with a "PC" style 4-pin Molex connector for power, unlike the
more usual 6-pin square connector used by all my other 8" drives. What I'd
like to confirm is whether this unit can actually run on 12VDC. It does not
seem to work correctly with 12V applied, which could suggest either that it
requires 24V or is defective.
Before I let the magic smoke out of it, does anyone know the proper voltages
for this drive?
Some empirical evidence:
- The unit has a 7812 (12V) 3-terminal regulator hung off what would
normally be the +12V line of the molex connector for, e.g. a 5.25" floppy
drive. That input goes through a 100ohm 5W resistor before hitting the
regulator. With 12V applied the drive, I see only 9.2V at the input to
the regulator and approx. 7V on the other side. Sure _looks_ like maybe
it's supposed to see +24V at the top of that resistor, doesn't it?
- With 12V applied, the head-load solenoid doesn't reliably pull in on its
own.
- Head stepper seems a bit anemic.
- I can hear the drive motor slow down from the drag when the heads are
loaded.
- Drive goes through some motions of writing, but won't verify or read
anything.
How luck should I feel? Should I apply +24V and keep my fingers crossed?
Anyone have one of these drives installed and be able to put a voltmeter
on it?
Steve
--
1 Nov
1 Nov
9:43 a.m.
On 31 Oct 2009 at 21:03, Steven Hirsch wrote:
- The unit has a 7812 (12V) 3-terminal regulator hung
off what would
normally be the +12V line of the molex connector for, e.g. a 5.25"
floppy drive. That input goes through a 100ohm 5W resistor before
hitting the regulator. With 12V applied the drive, I see only 9.2V at
the input to the regulator and approx. 7V on the other side. Sure
_looks_ like maybe it's supposed to see +24V at the top of that
resistor, doesn't it?
This drive sounds a *lot* like the Tandon 848, which also uses a 7812
to drop the +24 to +12. There's also an on-board jumper around the
7812 that allows the drive to work on +12 instead of +24.
There's a schematic in the TM848 product spec on bitsavers.
--Chuck
12:08 p.m.
Some empirical evidence:
The first thing I would do is trace the ground and +5V rails back to the
connecotr (if you've not done so already). They should be very easy to find.
- The unit has a 7812 (12V) 3-terminal regulator hung off what would
A 7812 is going to need more that 12V input :-)
normally be the +12V line of the molex connector for,
e.g. a 5.25" floppy
drive. That input goes through a 100ohm 5W resistor before hitting the
regulator. With 12V applied the drive, I see only 9.2V at the input to
the regulator and approx. 7V on the other side. Sure _looks_ like maybe
it's supposed to see +24V at the top of that resistor, doesn't it?
Indeed it does.
- With 12V applied, the head-load solenoid doesn't reliably pull in on its
own.
- Head stepper seems a bit anemic.
_Most_ 8" drives have 24V solenoids and motors.
The Archive Sidewinder QIC tape drive has a 4 pin Molex power connector,
and it uses +5V and +24V (the middle 2 pins being ground). I am told some
Sun workstations had power cables with molex connnectors on them, most of
which were +5V and +12V, but one was +5V and +24V for the tape drive. Woe
betide you if you got that one in the wrong place!
- I can hear the drive motor slow down from the drag when the heads are
loaded.
- Drive goes through some motions of writing, but won't verify or read
anything.
How luck should I feel? Should I apply +24V and keep my fingers crossed?
It's up to you. I'd problaby trace out the scheamtics to see just what
was going on. But to be honest, with that 7812, it's going to need more
than 12V, and 24V sounds likely.
-tony
12:40 p.m.
On Sun, 1 Nov 2009, Tony Duell wrote:
It's up to you. I'd problaby trace out the
scheamtics to see just what
was going on. But to be honest, with that 7812, it's going to need more
than 12V, and 24V sounds likely.
Bizarre speculation:
Since most 8" drives use 24V, is there a possibility that this is a 5v&12V
drive design, with the 7812 there to adapt it to 24V?
Is there ANYTHING on the drive connected to that pin of the connector that
does NOT go through the 7812? If not, could you feed it relatively clean
12V downstream from the 7812?
1:11 p.m.
On Sun, 1 Nov 2009, Fred Cisin wrote:
On Sun, 1 Nov 2009, Tony Duell wrote:
Yes. From what I can tell, power to the head-load and door-lock solenoids
is picked off directly from the +24V input. Looks like the motor PCB is
on the far side of the +12V regulator (uses a "pancake" style direct-drive
motor with a little speed-control board next to it).
Seems to work fine on 24V, which is a relief. This was a brand, spanking
new drive that came sealed in the anti-static bag. With a 1986
manufacturing date, it's the newest such unit in my collection.
Last hurdle is to figure out if I can setup to have the motor run only on
select. There are a few jumpers, but nothing obviously labeled for this
purpose. As it is, the motor starts as soon as the diskette is inserted
and breaks a photo-sensor - doesn't even need the latch closed. I'd be
very surprised if there wasn't a way to change this behavior, but without
documentation it may take some playing around.
Steve
--
It's up to you. I'd problaby trace out
the scheamtics to see just what
was going on. But to be honest, with that 7812, it's going to need more
than 12V, and 24V sounds likely.
Bizarre speculation:
Since most 8" drives use 24V, is there a possibility that this is a 5v&12V
drive design, with the 7812 there to adapt it to 24V?
Is there ANYTHING on the drive connected to that pin of the connector that
does NOT go through the 7812? If not, could you feed it relatively clean
12V downstream from the 7812?
2:11 p.m.
On 1 Nov 2009 at 12:40, Fred Cisin wrote:
Bizarre speculation:
Since most 8" drives use 24V, is there a possibility that this is a
5v&12V drive design, with the 7812 there to adapt it to 24V?
Is there ANYTHING on the drive connected to that pin of the connector
that does NOT go through the 7812? If not, could you feed it
relatively clean 12V downstream from the 7812?
That's the way the Tandon 848 works--there's an on-board jumper
around the 7812, so you can run it on either +24 or +12. (FWIW, this
is a drive with a +12VDC spindle motor; not the usual AC line-powered
one).
--Chuck
1:07 a.m.
From: "Steven Hirsch"
I just purchased one of these on ebay, but am unable to
find even a shred
of documentation on the web.
It's equipped with a "PC" style 4-pin Molex connector for power, unlike
the more usual 6-pin square connector used by all my other 8" drives.
What I'd like to confirm is whether this unit can actually run on 12VDC.
It does not seem to work correctly with 12V applied, which could suggest
either that it requires 24V or is defective.
What does the stepper motor say, if anything?
2:19 a.m.
I don't know that you would want to apply 24v across a 12v regulator,
might be less than that to be sufficient, maybe +18 or +15 to kick the
regulator output up to +12 you need.
Nico de Jong wrote:
From: "Steven Hirsch"
I just purchased one of these on ebay, but am
unable to find even a
shred of documentation on the web.
It's equipped with a "PC" style 4-pin Molex connector for power,
unlike the more usual 6-pin square connector used by all my other 8"
drives. What I'd like to confirm is whether this unit can actually
run on 12VDC. It does not seem to work correctly with 12V applied,
which could suggest either that it requires 24V or is defective.
What does the stepper motor say, if anything?
5:59 a.m.
On Sun, 1 Nov 2009, jim s wrote:
I don't know that you would want to apply 24v
across a 12v regulator, might
be less than that to be sufficient, maybe +18 or +15 to kick the regulator
output up to +12 you need.
I was feeling lucky, so I tried feeding it 24V on the pin leading to the
12V regulator. No smoke, all voltages looked rational on the board and
the unit started working properly :-).
Definitely a piece of information for the archives. First time I've seen
that particular PC-ish Molex connector used for anything other than
+5-GND-+12.
Now, if I could only figure out the proper jumpering to keep the drive
motor off until selected... There seems to be virtually no information
available on this unit. Best I can determine, it was an OEM part used by
GE medical imaging equipment.
Steve
--
2 Nov
2 Nov
9:20 a.m.
On 1 Nov 2009 at 8:59, Steven Hirsch wrote:
> Definitely a piece of information for the
archives. First time
I've
seen that particular PC-ish Molex connector used for
anything other
than +5-GND-+12.
This drive seems to have been used a lot on GE medical equipment (CT
Scan, YAG laser, etc.).
I daresay that you'll find a jumper on board that bypasses the
regulator to allow you to use +12, +5 as your supply. It makes
sense in that light to use the standard 5.25" style 4-pin Molex.
--Chuck
3:03 p.m.
On Mon, 2 Nov 2009, Chuck Guzis wrote:
On 1 Nov 2009 at 8:59, Steven Hirsch wrote:
Unfortunately, no. The solenoids need +24V.
Would love to find the technical information (jumpering, etc.) for this
drive.
Steve
--
> Definitely a piece of information for the
archives. First time
I've
seen that particular PC-ish Molex connector used
for anything other
than +5-GND-+12.
This drive seems to have been used a lot on GE medical equipment (CT
Scan, YAG laser, etc.).
I daresay that you'll find a jumper on board that bypasses the
regulator to allow you to use +12, +5 as your supply. It makes
sense in that light to use the standard 5.25" style 4-pin Molex.
3 Nov
3 Nov
9:41 a.m.
On 2 Nov 2009 at 18:03, Steven Hirsch wrote:
Unfortunately, no. The solenoids need +24V.
Solenoids, plural? For head-load and a door-lock?
Very strange indeed. Might this drive have been offered in a 5.25"
compatible configuration, without either solenoid? I wonder if
Matsushita made this particular drive variant solely for GE Medical?
--Chuck
5:54 p.m.
On Tue, 3 Nov 2009, Chuck Guzis wrote:
On 2 Nov 2009 at 18:03, Steven Hirsch wrote:
Correct.
Unfortunately, no. The solenoids need +24V.
Solenoids, plural? For head-load and a door-lock? Very strange indeed. Might this drive have been
offered in a 5.25"
compatible configuration, without either solenoid? I wonder if
Matsushita made this particular drive variant solely for GE Medical?
It's possible, I guess. Finally located the manual on Herb Johnson's
website and have ordered a copy. That may bring more information to
light.
For sure it's not a common model, but is very "modern" in its
construction. I'm guessing it could have been one of the latest (if not
THE latest) 8" drive design marketed.
Steve
--
2 Nov
2 Nov
11:51 a.m.
I don't know that you would want to apply 24v across a 12v regulator,
It's quite possible (in fact I would say 'likely') that the raw 24V is
used for things like the motors and head load solenoid, and is regulated
down to 12V for the read amplifier, etc. In which case you would need 24V
input
-tony
1:12 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: Monday, November 02, 2009 11:51 AM
To: cctalk at classiccmp.org
Subject: Re: Panasonic JA751 8" drive question
IIRC, the common LM78xx regulators were fine with input up to 40v. -- Ian
I don't know that you would want to apply 24v across a 12v regulator,
It's quite possible (in fact I would say 'likely') that the raw 24V is
used for things like the motors and head load solenoid, and is
regulated
down to 12V for the read amplifier, etc. In which case you would need
24V
input
-tony
1 Nov
1 Nov
5:30 a.m.
On Sun, 1 Nov 2009, Nico de Jong wrote:
From: "Steven Hirsch"
No markings at all on the stepper motor. But, all the caps on the board
are 50V rating.
--
I just purchased one of these on ebay, but am
unable to find even a shred
of documentation on the web.
It's equipped with a "PC" style 4-pin Molex connector for power, unlike the
more usual 6-pin square connector used by all my other 8" drives. What I'd
like to confirm is whether this unit can actually run on 12VDC. It does not
seem to work correctly with 12V applied, which could suggest either that it
requires 24V or is defective.
What does the stepper motor say, if anything?
5527
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18 comments
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ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
cisin＠xenosoft.com -
IanK＠vulcan.com -
jws＠jwsss.com -
nico＠farumdata.dk -
snhirsch＠gmail.com