> Date: Wed, 4 May 2011 21:36:32 EDT
> From: JHMcCarthy at aol.com
> Subject: Re: Drive Type International Memories, Inc. (IMI) 5012H
> To: cctech at classiccmp.org
> Message-ID: <c892a.3319ecda.3af35920 at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
> Just a historical question. I have a 10 MB IMI drive that was going to
> be
> used in the IBM PC-XT back in 1983. Is IMI still in existence? Was it
> located in Oregon in 1983? --- Jud
>
> Justin (Jud) McCarthy
> 251 SW 9th Ave
> Boca Raton, FL 33486
> Home (561)391-1422 Cell: (561)504-7048
> jhmccarthy at aol.com
The IMI 10 MB was never used in the IBM PC/XT; IBM's suppliers were Seagate,
MiniScribe and CMI. The IMI drive was likely used in clones.
CMI is most famous for its exclusive contract to supply the PC/AT drives
which then almost sunk the AT due to their high apparent failure rate. If
anyone has a copy of the Core International advertisement offering to build
a breakwater at Boca with trade-ins I'd love a copy.
Only Seagate survived.
Tom
Just a historical question. I have a 10 MB IMI drive that was going to be
used in the IBM PC-XT back in 1983. Is IMI still in existence? Was it
located in Oregon in 1983? --- Jud
Justin (Jud) McCarthy
251 SW 9th Ave
Boca Raton, FL 33486
Home (561)391-1422 Cell: (561)504-7048
jhmccarthy at aol.com
Having been given, some time ago, 2 8/L core memory stacks to test and then sell, I set about and fired up my 8/L. This 8/L was bought some years ago for around 500 USD, in known working condition. Try this today....
The memory tests revelead that one stack was nearly OK, the other was seriously sick.
The nearly OK one was 99.9% OK, but bit 0 @ address 0 was stuck. I intended to live with that, until it was pointed out on classiccmp that address 0 is very essential indeed....
I decided to take the plunge and tried to repair the memories.
The sick module was checked out first. Result : around 20 of the select diodes were either shorted, or open ciruit. Further tests show that the coremats themselves were also sick : resistence of sense and inhibit wires varied widely ( normal values are around 19 ohms vor inhibit, 24 ohms for sense wires ). Select wires were all OK.
So the stack, made by Dataram, was opened by cutting through 128 wires and separating the upper diode board from the stack. Then the microscope was fired up and I produced some pictures :
An overview of the coremat :
ftp://jdreesen.dyndns.org/ftp/Cores/coremat.jpg
Strange to find was a whole bunch of very small cupper wire remains, which where below some lacquer, which means they must have been there since the beginning :
ftp://jdreesen.dyndns.org/ftp/Cores/wire_remains.jpg
A whole bunch of repairs, covered by some gunk was found. These also were made during production. They were present only on the sense and inhibit wires :
ftp://jdreesen.dyndns.org/ftp/Cores/old_repair.jpg
Wait a minute : only on the sense and inhibit wires? which where also the wires with the variables resistance ?
So I took out the smallest tip SMD iron I could find and started resoldering these old repairs. See
ftp://jdreesen.dyndns.org/ftp/Cores/new_repair.jpgftp://jdreesen.dyndns.org/ftp/Cores/new_repair2.jpgftp://jdreesen.dyndns.org/ftp/Cores/new_repair_3.jpg
And yes, with each repair one more sense or inhibit wire was OK. Yes ! Good !
Until, with one of the last repairs, the inhibit wire broke, some few mm inside the coremat...
ftp://jdreesen.dyndns.org/ftp/Cores/broken_inhibit.jpg
In this picture you can seen the green select wire in the middle, which no longer has an accompaning inhibit wire.
The other core lines still have the inhibit wire, in parallel with the select line.
Major bugger, since the inhibit line is the lowest of the four wires in each core....
I attempted repair by trying to pull out the whole inihibit wire from that line of cores, only to have it break in several more places....
Endgame for this particular stack.....
... and some weeks later i did open the other stack, made by Fabritek.
First impression was much better than the Dataram stack, no loose copper wire segments, the pic shows it all :
ftp://jdreesen.dyndns.org/ftp/Cores/coremat_ft.jpg
Also far fewer repairs on this one, and much better organized : instead of just soldering the wire-ends together, the wires are soldered together in some spare PCB holes that are sprinkled about the area for that purpose.
ftp://jdreesen.dyndns.org/ftp/Cores/wire_hole.jpgftp://jdreesen.dyndns.org/ftp/Cores/wire_hole2.jpg
The reason of the stack failure was soon apparant, see :
ftp://jdreesen.dyndns.org/ftp/Cores/core_broken_ov_ft.jpg
In even greater detail the broken core can be seen here :
ftp://jdreesen.dyndns.org/ftp/Cores/core_broken_ft.jpgftp://jdreesen.dyndns.org/ftp/Cores/core_broken2_ft.jpg
I strongly suspect mechanical stresses are biggest in the corner, which I assume is why this particulare core was broken. But since this core is situated in the coremat corner, surely a repair must be possible ?
I started with cleaning out the remains of the wires that connect the coremat-pcb with the diodeboard.
And yes it had to happen : a small shift of the soldering iron, and one select line was broken...
ftp://jdreesen.dyndns.org/ftp/Cores/omg.jpgftp://jdreesen.dyndns.org/ftp/Cores/omg2.jpg
Luckily it was outside the stack, so the wire could be repaired
ftp://jdreesen.dyndns.org/ftp/Cores/omg_repaired.jpg
Then I took some individual cores from the Dataram mat, here they are, with a small piece of flatcable for size comparison :
ftp://jdreesen.dyndns.org/ftp/Cores/cores.jpgftp://jdreesen.dyndns.org/ftp/Cores/cores2.jpgftp://jdreesen.dyndns.org/ftp/Cores/cores3.jpg
This is the overal location of the broken core repair, the mat edge, with x/y select and sense/inhibit wires.
ftp://jdreesen.dyndns.org/ftp/Cores/pcb_edge.jpgftp://jdreesen.dyndns.org/ftp/Cores/pcb_edge_2.jpgftp://jdreesen.dyndns.org/ftp/Cores/pcb_edge_3_ft.jpg
So first the X select line was opened, a core was inserted, and the select line soldered in again. See :
ftp://jdreesen.dyndns.org/ftp/Cores/inhibit2.jpg
Next line was the inhibit line, the picture also clearly shows the old, broken, core
ftp://jdreesen.dyndns.org/ftp/Cores/inhinit_mounted.jpg
And the sense and Y select wires were routed through :
ftp://jdreesen.dyndns.org/ftp/Cores/repair_full.jpgftp://jdreesen.dyndns.org/ftp/Cores/repair_full_close.jpg
Select, sense and inhibit wires where then measured and found to be OK. I was astonished to find that the Cu-wires on this stack were considerably less brittle than the ones of the Dataram stack, although visually they are the same.
Pending a company move, the whole setup was now set away for a few weeks.
In the new lab I set about reassembling the stack.
Which is when disaster struck ... The new magnifying glass setup was unstable and landed where it could cause maximal damage : the coremat itself, with around 40 cores broken........
Major major bummer, and really only myself to blame. Not only was the stack now lost, but I also now cannot produce evidence that the core repair worked.
So in conclusion : can core memory stacks be repaired ?
Potentially yes, but it is every bit as difficult as you would expect, and only certains failure modes are repairable. In the 8L stack an additional difficulty is the way the stack is build up with 128 wires to be snipped, 128 holes to be cleaned and to be rewired, all without damaging the cores.
So i now have 2 stacks, one Fabritek, one Dataram, both opened. Mechanical differences prevent building one good stack from the two damaged ones.
The Fabritek has two known good coremat-pcb's, the Dataram has two potentially good coremat PCB's.
I have spent rather too much time on this, and am open to offers on these stacks, in the condition described above.
If someone wants to sell their known-defective 8L / 8I Dataram/Fabritek corestacks, I would also be interested.
Jos Dreesen
Sorry if this system is still off topic...
I have a full set of guts for the 2-CPU version of the Digital AlphaServer
4100. No CPUs, no memory, no expansion boards, no fans, no PSUs, no disks,
but all the other parts that could be removed, down to the little metal
clips that make an electrical connection between the case and the cover.
http://alexeyt.freeshell.org/AS4100_parts.jpg
Here's what happened: I got 2 of incomplete systems in the early 2000s,
and put them away to play with 'later'. Then I had to move, so I decided I
could keep just one. I took out everything in the less complete system
that could be removed, and boxed it up. The more complete one went in the
basement of the new house. Fast forward 2 years or so: there's a flood in
the basement, and the 'good' AS4100 dies under a foot of water :-( By the
time the basement dried out enough to get to it, it was so rusted I was
unable to open the case. It did, however, save the lives of a half-dozen
other machines that were stacked on top of it.
For some reason I kept hanging on to the box of spare parts... I have no
way of using these, so I figure I sould give them to someone who can.
They're yours for the cost of shipping from 27606; it's about 5-6 pounds
all told (I'm guessing, I don't have a scale).
Alexey
>From Myles Swift:
"Please do post it on the Classic list. I have some other items to
sell as well - 8 inch external floppy drive, 2 Kaypro 10s, one is #49
>from the first run that I pre-ordered. I also have an original IBM PC
with a Tall Trees card and a 5 MB CDC hard drive with the lock bar. I
have an ATR-8000. That ATR was the first unit with a programmable
floppy controller so you could burn floppies for different systems. I
think it was designed as an Atari add-on device. That business died
when Kaypro included Uniform to perform that function. I also have a
Compaq 386, the one that really put Compaq into high gear.
I figured I would try offering the heavy stuff locally first before
going to ebay. You can forward this list of items to see if anyone on
the Classic list is interested. "
He also has a Cipher F880 1/2" drive with Cipher S100 controller
card. He also says that he's looking for a Pertec Interface Q-bus
card.
Contact Myles at mswift "at" computerassistance.com.
Cheers,
Chuck
On Tue, Apr 26, 2011 at 7:34 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
> We (RICM) have an 8/I with 5x TU55 drives, a pair of bare 8/L, and a
> very functional 8/S that now runs FOCAL.
Did you have to do any work on that -8/S? I have one that needs a lot
of replacement bulbs and some sleuthing in the "lock" circuit (the
switch is fine, but the machine behaves as if it's always in "lock"
mode). I've done lots of work on M-series machines like the -8/L and
-8/i (it's where I got my start with 12 bits), but virtually no
debugging of the older logic. I built a simple M-series FLIP-CHIP
tester with a DEC backplane socket and an 6821 PIA, but it was
straightforward to abstract different arrangements of inputs and
outputs for different modules. I haven't done the homework to see how
many types of R/S-series modules are used in a Straight-8 or -8/S, so
I'm not even sure how difficult it would be to make a comparable logic
tester. I'd like to automate the testing to the point where I could
at least plug in a suspect module and either flip some switches or
type some commands to exercise the inputs and monitor the outputs -
yes, one can debug pre-TTL machines with a lot of clip leads and an
oscilloscope, but I'd like to abstract that one level to see what
boards need detailed attention.
Has anyone ever considered building an automated or semi-automated
R/S-Series module tester? Did it get further than musings and
drawings?
-ethan
>
> If I am not mistaken, the chopper transistor you are referring to is Q1
> (p88). I checked the resistance with the component still soldered onto the
Correct.
> board. Looking at it from the front (with a plate behind connected to what
> looks like a diode), the resistance between the middle and the left pin
was
> 170Kohm (or 1Mohm, the multimeter scaling confuses me somewhat, I get
> different numbers depending on whether I put the dial on 200K or 2M,
either
Well, it's not totally shorted, then, which is the common failure mode of
chopper transistors.
Does your meter have a 'diode check' range? If so, use that, and check the
base-emitter and base-collector junctions with the probes both ways round.
This will at least tell you if the junctions are good. You really need to
remove the transistor from the PCB to test it, though.
But perhaps before that we should check a few more things. The chopper
circuit
is driven by E2 (p88), a good ol' 555 timer wired as an astable. For this to
work, it needs to be gettign power. This power comes from one of two places
:
When the supply is running, it comes from T1 on the PSU motherboard, via
pins
7 and H of the connector and diode D7 (p88).
At start-up it comes from the mid-point of the mains smoothing capacitors
via
pins 2 and B and Q6 (p88). The base of Q6 is driven from the network R2
and D2
(p82). You should check the power resistors on the motherboard, actually,
R1, R2 and R3 (p82).
Now obviously the first can't be doing anything since the supply is not
running. But the second source should be there. You should measure the
supply voltage at pin 8 of E2 _with respect to pin 1 of E2_. That is, the
black meter probe is connected to pin 1 of E2, the red one to pin 8 of the
same IC. Be warned that this circuitry is directly connected to the mains,
and will have _lethal_ voltages on it with repect to ground. So connect the
wires, make sure they can't touch anything, then plug the machine in and
see
what voltage you get. Unplug the mains and wait for things to discharge
before
touching anything.
-tony
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I've seen several mentions on here of folks using LJ5 printers... I recently
acquired as part of a govt auction, a C3768A Lj5 SI paper handler board and a
Token Ring Jetdirect card with Lj5SI drivers for several O/Ss. Status is
unknown although they *look* unused in original boxes. Anyone interested can
have them for postage from 95006 (I suspect they would fit a medium flat rate
box).
Steve
>> Is it really the knowledge that's fading away or the technique?
>>
>> I mean, seriously, there is nothing complicated about core planes.
>> Its a bunch of toroids with wires strung through them.
>
> Tricks of the trade that make the job easier.
>
> One of the better known tricks it to pull apart a wire to be strung
> though a line of cores, rather than cutting it normally, so you get a
> little bit of a needle like tapered end on the wire.
One odd thing about these attitudes we have, is that we're almost all male and the folks
who did and understood the work and improved the techniques were almost exclusively female.
It's sort of like the boatanchor radio groups where we have men lecturing other men
as to how to lace cables or properly wrap a wire around a lug before soldering.
The women who actually did the work would laugh at all of us :-). I know they laughed
at me and other male techies (anywhere from undergrads to professional machinists to
full professors!) who sometimes attempted these sorts of tasks!
Tim.
A friend of mine (who's been trying to join this list!) needs help
rescuing something from the Berkeley California area. Contact him
privately at ark72axow at msn.com.
