6 Apr
2010
6 Apr
'10
2:33 p.m.
Hello,
I'm repairing my A1010 Amiga external floppy drive - the actual drive
works (tested by plugging it into the internal A500 floppy connector),
so the fault should be on the latch board inside; there are two chips,
a 74LS74 D Flip-Flop and one chip (also 14 pin) with number M53238P
preceded by the Mitsubishi logo. Given the required function, and
connections on the adapter board, I am 99% sure that it's a 74LS38
Quad NAND open-collector equivalent - but googling doesn't turn up a
datasheet, just a gazillion chinese parts vendors. Can someone just
confirm this in a cross-reference? Or a A1010 schematic? Or their own
drive?
Thanks,
Joe.
PS. Symptom is that the drive clicks but never spins. I've already
taken out the chips and replaced them - this time in sockets. So if
I'm wrong it's a simple matter of undoing the 20-odd screws yet again
(Verdammte Post mit deren entstoerregelungen von damals...) and
replacing the chip. I just want to double-check before plugging it
into the A500 again tonight.
--
Joachim Thiemann :: http://www.tsp.ece.mcgill.ca/~jthiem
6 Apr
6 Apr
2:39 p.m.
On Tue, Apr 6, 2010 at 1:33 PM, Joachim Thiemann <joachim.thiemann at gmail.com
wrote:
Can someone just
confirm this in a cross-reference? Or a A1010 schematic? Or their own
drive?
It's the same mechanism in an amiga 1000 (iirc) if anyone has that instead.
I have an a1010 floating around somewhere, but I'm not much of a hardware
person. If no one else beats me to it, I'll see if I can find it.
brian
7 Apr
7 Apr
6:17 p.m.
Brian Lanning wrote:
On Tue, Apr 6, 2010 at 1:33 PM, Joachim Thiemann
<joachim.thiemann at gmail.com
Sounds familiar for an A500, too - at least I recall two ICs and some pull-up
resistors. I remember building interfaces like that so we could use junked PC
floppy drives as external drives (the prices that Commodore wanted for
'official' external drives were insane)
cheers
Jules
wrote:
Can someone just
confirm this in a cross-reference? Or a A1010 schematic? Or their own
drive?
It's the same mechanism in an amiga 1000 (iirc) if anyone has that instead.
6:55 p.m.
On Wed, Apr 7, 2010 at 18:17, Jules Richardson
<jules.richardson99 at gmail.com> wrote:
Sounds familiar for an A500, too - at least I recall
two ICs and some
pull-up resistors. I remember building interfaces like that so we could use
junked PC floppy drives as external drives (the prices that Commodore wanted
for 'official' external drives were insane)
Yes, and the 'trick' was actually well documented. I have in a copy
of "The Amiga System Programmer's Manual" but I seem to recall it on
Aminet as well. Basically, make sure the drives are set to DS0 (IIRC
stock PC drives are set to DS2) and then latch the disk motor line
with the drive select, so that 4 drives can sit on one cable.
Anyways quick update: the drive now works, but only on my A1000, not
the A500; same symptoms. I think the LS'38 on the A500 motherboard is
blown, too, it seems to not pull the motor line low enough.
Bummer. I'm not good at desoldering chips without potential damage to
the board.
Joe.
--
Joachim Thiemann :: http://www.tsp.ece.mcgill.ca/~jthiem
11:41 p.m.
On Wed, Apr 7, 2010 at 22:31, Alexandre Souza - Listas
<pu1bzz.listas at gmail.com> wrote:
That's what I ended up doing on the 1010 - but the chips were put in
all the way so that the only exposed part of the legs were the 'fat'
portion - there was very little room in between to get a pair of side
cutters in there and I had to apply a lot of force. If I slip, that
would be no good... nevertheless, that's probably what I'll end up
doing (the cutting, not the slipping part!)
Joe.
--
Joachim Thiemann :: http://www.tsp.ece.mcgill.ca/~jthiem
Bummer.
?I'm not good at desoldering chips without potential damage to
the board.
? Why not cut the pins of the IC very near the ic body, and later heat the
pins and pull it with a pair of tweezers? It **IS** easy! 
8 Apr
8 Apr
6:36 a.m.
That's what I ended up doing on the 1010 - but the chips were put in
all the way so that the only exposed part of the legs were the 'fat'
portion - there was very little room in between to get a pair of side
cutters in there and I had to apply a lot of force. If I slip, that
would be no good... nevertheless, that's probably what I'll end up
doing (the cutting, not the slipping part!)
==========
There is a kind of side cutters (a "slim" type) well suited to places
like this, lemesee if I can find a photo on the net...here!
http://www.scalemodelguide.com/media/images/2009/02/01/Xuron_side_cutters_1…
This is a very thin cutter, you can use to cut the legs very near the
body of the ICs :)
3:15 p.m.
On Wed, Apr 7, 2010 at 22:31, Alexandre Souza - Listas
<pu1bzz.listas at gmail.com> wrote:
the
You can (or at least could) get cutters almost designed for this sort of
job. Essentailly a flsh-cutting end cutter. Most of the manufacturers of
precision pliers/cutters (LIndstrom, CK, etc) make them. If you go to a
good tool shop, you can problably get a pair (but be waned they will not
be cheap!).
-tony
Bummer.
=A0I'm not good at desoldering chips without potential damage to
the board.
=A0 Why not cut the pins of the IC very near the ic body, and later heat = pins and pull it with a pair of tweezers? It
**IS** easy!
That's what I ended up doing on the 1010 - but the chips were put in
all the way so that the only exposed part of the legs were the 'fat'
portion - there was very little room in between to get a pair of side
cutters in there and I had to apply a lot of force. If I slip, that 
3:59 p.m.
On Thu, Apr 8, 2010 at 3:15 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
You can (or at least could) get cutters almost
designed for this sort of
job. Essentailly a flsh-cutting end cutter. Most of the manufacturers of
precision pliers/cutters (LIndstrom, CK, etc) make them. If you go to a
good tool shop, you can problably get a pair (but be waned they will not
be cheap!).
Cheap tools are rarely good and vice versa.
My fingers and eyes are too valuable for cheap tools.
-ethan
9 Apr
9 Apr
1:38 p.m.
Cheap tools are rarely good and vice versa.
I can't disgree with that.
My fingers and eyes are too valuable for cheap tools.
In this case, I would be more worred that a cheap pair of cutters would
exert so much force on the IC pin that it would damage the PCB.
-tony
(I am not rich enough to buy cheap tools :-))
6 Apr
6 Apr
2:41 p.m.
From: joachim.thiemann at gmail.com
Date: Tue, 6 Apr 2010 14:33:17 -0400
Subject: Can someone confirm this chip equivalence?
To: cctalk at classiccmp.org
Hello,
I'm repairing my A1010 Amiga external floppy drive - the actual drive
works (tested by plugging it into the internal A500 floppy connector),
so the fault should be on the latch board inside; there are two chips,
a 74LS74 D Flip-Flop and one chip (also 14 pin) with number M53238P
preceded by the Mitsubishi logo. Given the required function, and
connections on the adapter board, I am 99% sure that it's a 74LS38
Quad NAND open-collector equivalent - but googling doesn't turn up a
datasheet, just a gazillion chinese parts vendors. Can someone just
confirm this in a cross-reference? Or a A1010 schematic? Or their own
drive?
Hi Joe
The 74LS38 may not have the current out needed. It may have
needed a 7438. As I recall, these have a stronger drive ( I could
be wrong here but that is what I remember ).
Dwight
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2:48 p.m.
On Tue, Apr 6, 2010 at 2:41 PM, dwight elvey <dkelvey at hotmail.com> wrote:
Hi Joe
?The 74LS38 may not have the current out needed. It may have
needed a 7438. As I recall, these have a stronger drive ( I could
be wrong here but that is what I remember ).
The 7438 does have a stronger current drive than a 74LS38, but I do
not recall if the A1010 needs that or not.
-ethan
3:02 p.m.
On Tue, Apr 6, 2010 at 14:48, Ethan Dicks <ethan.dicks at gmail.com> wrote:
The 7438 does have a stronger current drive than a
74LS38, but I do
not recall if the A1010 needs that or not.
Hmmm, I could open it up again and check the value of the pull-up
resistor pack - that should be a good indicator of the current the
gates have to sink.
Joe.
(Brian, don't open the 1010 if you don't have to. It's a pain.)
--
Joachim Thiemann :: http://www.tsp.ece.mcgill.ca/~jthiem
3:48 p.m.
Hello,
I'm repairing my A1010 Amiga external floppy drive - the actual drive
works (tested by plugging it into the internal A500 floppy connector),
so the fault should be on the latch board inside; there are two chips,
a 74LS74 D Flip-Flop and one chip (also 14 pin) with number M53238P
preceded by the Mitsubishi logo. Given the required function, and
connections on the adapter board, I am 99% sure that it's a 74LS38
Quad NAND open-collector equivalent - but googling doesn't turn up a
I am pretty ssre it's the same pinout and function. I t may well haev
differente drive caracteristics, but thit probably deosn't matter. A '38
whould work fine.
PS. Symptom is that the drive clicks but never spins.
I've already
taken out the chips and replaced them - this time in sockets. So if
I'm wrong it's a simple matter of undoing the 20-odd screws yet again
(Verdammte Post mit deren entstoerregelungen von damals...) and
Does that have an English translation that can bve used in polite
compnay :-)
replacing the chip. I just want to double-check
before plugging it
into the A500 again tonight.
-tony
5179
days inactive
5182
days old
13 comments
7 participants
participants (7)
-
ard＠p850ug1.demon.co.uk -
brianlanning＠gmail.com -
dkelvey＠hotmail.com -
ethan.dicks＠gmail.com -
joachim.thiemann＠gmail.com -
jules.richardson99＠gmail.com -
pu1bzz.listas＠gmail.com