3 Jan
2017
3 Jan
'17
10:47 a.m.
On Tue, 1/3/17, Cory Heisterkamp <coryheisterkamp at gmail.com> wrote:
What I?m wondering is if anyone is familiar with the
setup/adjustment
procedure for getting the heads set correctly. There *might* be a couple of
unused tracks I can relocate heads to, but my thought is that if half a
dozen heads were already in contact, then the rest may be perilously close
as well (swelled drum?). My odds of setting 71 heads perfectly on a 50 year
old worn drum is?well?not great.
A while back I read a procedure (probably in reference to the G-15).
Quite frankly, it scared me a little, but I'll pass it on. The idea is to
use sound. The tech would use a screwdriver as a sounding bar
between the casing and his ear. Then the head was tightened down
until you could just hear it start to brush. I don't remember for sure,
but I'd have to think that you would then back off just enough for
the brushing sound to stop. I don't recall whether the article said
that this was done with the motor running or the drum was being turned
by hand, but if it were my machine, I'd set the heads turning the drum
slowly by hand and then check for any brushing sound when the motor
comes up.
Whether or not the drum is restorable, I'd still plan on building a drum
simulator. That way you can get the rest of the machine up and
running without stressing or depending on the drum too much. Plus
if the drum does turn out to be unrestorable, you'll still be able to
run the rest of the machine. As to how to approach the simulator,
I would have to think a C.H.I.P. or a Pi would have plenty of horsepower,
especially if you drop Linux and either run on the bare metal or
as an in-kernel driver in something lighter weight.
BLS
3 Jan
3 Jan
11:57 a.m.
On Tue, Jan 3, 2017 at 1:47 PM, Brian L. Stuart <blstuart at bellsouth.net wrote:
On Tue, 1/3/17, Cory Heisterkamp <coryheisterkamp
at gmail.com> wrote:
This sounds believable (but scary). With the 64 main heads out of the way,
I pulled out a mechanic's stethoscope last night and carefully rocked with
the drum back and forth listening to the recirculating register heads. One
may need backed off just a little, but the adjustment screws are a little
crude.
What I?m wondering is if anyone is familiar with
the setup/adjustment
procedure for getting the heads set correctly. There *might* be a couple
of
unused tracks I can relocate heads to, but my
thought is that if half a
dozen heads were already in contact, then the rest may be perilously
close
as well (swelled drum?). My odds of setting 71
heads perfectly on a 50
year
old worn drum is?well?not great.
A while back I read a procedure (probably in reference to the G-15).
Quite frankly, it scared me a little, but I'll pass it on. The idea is to
use sound. The tech would use a screwdriver as a sounding bar
between the casing and his ear. Then the head was tightened down
until you could just hear it start to brush. I don't remember for sure,
but I'd have to think that you would then back off just enough for
the brushing sound to stop. I don't recall whether the article said
that this was done with the motor running or the drum was being turned
by hand, but if it were my machine, I'd set the heads turning the drum
slowly by hand and then check for any brushing sound when the motor
comes up.
Whether or not the drum is restorable, I'd still plan on building a drum
simulator. That way you can get the rest of the machine up and
running without stressing or depending on the drum too much. Plus
if the drum does turn out to be unrestorable, you'll still be able to
run the rest of the machine. As to how to approach the simulator,
I would have to think a C.H.I.P. or a Pi would have plenty of horsepower,
especially if you drop Linux and either run on the bare metal or
as an in-kernel driver in something lighter weight.
BLS
Once I can make sense of the timing tracks, I think I'll proceed with this.
Not sure how I feel about using a micro-based solution though. Just seems
wrong : ) -C
12:15 p.m.
On 01/03/2017 12:57 PM, Cory Heisterkamp wrote:
Once I can make sense of the timing tracks, I think
I'll proceed with
this. Not sure how I feel about using a micro-based solution though.
Just seems wrong : ) -C
If enough working heads can be found, the drum probably can be
remanufactured, as according to this:
http://miriam-english.org/files/drum-computers/drum-computers.html
the drum was nickel-chromium plated, not ferric oxide. This is what I
would have suspected, as coating equipment and binders would probably be
a far cry from modern technology back then, where precision plating was
already an established art.
--Chuck
12:19 p.m.
On Jan 3, 2017, at 4:15 PM, Chuck Guzis <cclist at
sydex.com> wrote:
On 01/03/2017 12:57 PM, Cory Heisterkamp wrote:
Metal alloy plating seems common in fixed head disks also, at least in the ones from DEC I
have seen. Making a new drum sounds like a great class project for an ambitious machine
shop student.
paul
Once I can make sense of the timing tracks, I
think I'll proceed with
this. Not sure how I feel about using a micro-based solution though.
Just seems wrong : ) -C
If enough working heads can be found, the drum probably can be
remanufactured, as according to this:
http://miriam-english.org/files/drum-computers/drum-computers.html
the drum was nickel-chromium plated, not ferric oxide. This is what I
would have suspected, as coating equipment and binders would probably be
a far cry from modern technology back then, where precision plating was
already an established art. 
12:42 p.m.
On Tue, Jan 03, 2017 at 04:19:01PM -0500, Paul Koning wrote:
Making a new drum sounds like a great class project
for an ambitious
machine shop student.
Very ambitious. IIRC for the G-15 there is/are (one? two?) timing track(s)
which were written at the factory. Of course whatever that machine was,
has not survived. I remember reading that if you lost that timing track,
your machine was toast.
mcl
2:07 p.m.
On 01/03/2017 01:42 PM, Mark Linimon wrote:
Very ambitious. IIRC for the G-15 there is/are (one?
two?) timing
track(s) which were written at the factory. Of course whatever that
machine was, has not survived. I remember reading that if you lost
that timing track, your machine was toast.
Maybe. ISTR that wehn CE's were working on the CDC STAR station drums,
they routinely rewrote timing tracks. I recall that their only tools
were a scope and a Halliburton CE box. Apparently, the goal was write a
track such that there was no detectable "splice" in the beginning/end of
the track. Pretty much a cut-and-try operation.
Perhaps the LGP30 is similar.
--Chuck
4:22 p.m.
On Jan 3, 2017, at 6:07 PM, Chuck Guzis <cclist at
sydex.com> wrote:
On 01/03/2017 01:42 PM, Mark Linimon wrote:
The fixed head disk I saw rebuilt in the field was a DEC RF11 -- it had basically its
entire guts replaced from spare parts. That included a new platter, so its timing track
had to be written. The timing track writer box had a knob on it to tweak the clock
frequency, and it worked just as you describe: keep hitting the "write track"
button and tweak the knob until the track gap checker circuit said the gap size was within
the required range.
The key questions for reconstructing such a device is what the modulation scheme is, and
the pulse pattern. There might be marker pulses for sector start, for example, or that
might just be derived from a counter in the controller.
paul
Very ambitious. IIRC for the G-15 there is/are
(one? two?) timing
track(s) which were written at the factory. Of course whatever that
machine was, has not survived. I remember reading that if you lost
that timing track, your machine was toast.
Maybe. ISTR that wehn CE's were working on the CDC STAR station drums,
they routinely rewrote timing tracks. I recall that their only tools
were a scope and a Halliburton CE box. Apparently, the goal was write a
track such that there was no detectable "splice" in the beginning/end of
the track. Pretty much a cut-and-try operation. 
4:42 p.m.
On 1/3/17 5:22 PM, Paul Koning wrote:
The key questions for reconstructing such a device is
what the modulation scheme is, and the pulse pattern.
There are running LGP-30s. Should be short work with a digital oscillosope to capture the
flux changes.
Hopefully, someone has done this already.
Someone should do the same for the surviving G-15s as well. I think Paul Pierce's
machine is at LCM now.
4:50 p.m.
On 1/3/17 5:42 PM, Al Kossow wrote:
Someone should do the same for the surviving G-15s as
well. I think Paul Pierce's machine is at LCM now.
turns out we have it
http://www.computerhistory.org/collections/catalog/102728118
4 Jan
4 Jan
2:58 a.m.
On Tue, 3 Jan 2017, Al Kossow wrote:
There are running LGP-30s. Should be short work with a
digital
oscillosope to capture the flux changes. Hopefully, someone has done
this already.
Of course, we did this initially in 1999 when we got our first LGP-30, and
a couple of times later on. The last time was a few months ago when we
suspected a bad sector/track, but it turned out that there was a 50 Hz hum
on the read amplifier supply voltage (an electrolytic cap on a module lost
its capacity).
We both have analog recordings (from digitizing scopes) and logic analyzer
dumps. So concerning the LGP-30, all relevant information about the drum
has been saved :-)
Christian
6:03 a.m.
On Wed, 4 Jan 2017, Christian Corti wrote:
On Tue, 3 Jan 2017, Al Kossow wrote:
> There are running LGP-30s. Should be short work with a digital oscillosope
....
We both have analog recordings (from digitizing
scopes) and logic analyzer
dumps. So concerning the LGP-30, all relevant information about the drum has
been saved :-)
We have a second LGP-30 drum in our museum. It is damaged by water.
(large rusted areas, probably from water between heads and drum).
I'm dreaming to wash the brown oxide coating off with a solvent like
acetone, polish the drum and repaint it.
As magnetic paint I would try iron oxide from audio tapes solved in
acetone or some other solvent.
Perhaps one could ask an airbrush artist to do this.
Rumours say, that the drums originally also were coated "by hand".
Rewriting the timing tracks should not be impossible with todays
electronics.
There is another guy here in germany, who has a LGP-30 with heavily
corroded drum. That would be certainly interesting for him.
Klemens
--
klemens krause
Stuttgarter KompetenzZentrum fyr Minimal- & Retrocomputing.
http://computermuseum.informatik.uni-stuttgart.de
6:19 a.m.
On 1/4/17 7:03 AM, Klemens Krause wrote:
We have a second LGP-30 drum in our museum. It is
damaged by water.
(large rusted areas, probably from water between heads and drum).
I'm dreaming to wash the brown oxide coating off with a solvent like
acetone, polish the drum and repaint it.
As magnetic paint I would try iron oxide from audio tapes solved in acetone or some other
solvent.
Perhaps one could ask an airbrush artist to do this.
Rumours say, that the drums originally also were coated "by hand".
In doing some disk research recently, I came across a footnote for a rather unlikely
place to find information on magnetic coatings, which I just got a copy of:
Patton "Pigment Handbook Volume II Applications and Markets" 1973
Kurt Kreiselmaier "Pigmentation of Magnetic Tapes" pp 315-329
Which goes through the whole process at a high level of how magnetic tape is made,
including aligning all the magnetic particles on the surface. They also mention sperm
oil being used as one of the ingredients (I had wondered if there was documentation
for that claim), and about two dozen patents at the end.
There is also a lot of information in the book on colorizing agents for plastics.
I'll put a scan up today under midwesternUniveristy, where Kreiselmaier was an asst
prof.
6:56 a.m.
On 1/4/17 10:19 AM, Al Kossow wrote:
On 1/4/17 7:03 AM, Klemens Krause wrote:
> We have a second LGP-30 drum in our museum. It is damaged by water.
> (large rusted areas, probably from water between heads and drum).
> I'm dreaming to wash the brown oxide coating off with a solvent like
> acetone, polish the drum and repaint it.
> As magnetic paint I would try iron oxide from audio tapes solved in acetone or some
other solvent.
> Perhaps one could ask an airbrush artist to do this.
> Rumours say, that the drums originally also were coated "by hand".
>
The was a post application "calendaring" process to get a uniform
smooth
surface.
In doing some disk research recently, I came across a
footnote for a rather unlikely
place to find information on magnetic coatings, which I just got a copy of:
Patton "Pigment Handbook Volume II Applications and Markets" 1973
Kurt Kreiselmaier "Pigmentation of Magnetic Tapes" pp 315-329
Which goes through the whole process at a high level of how magnetic tape is made,
including aligning all the magnetic particles on the surface. They also mention sperm
oil being used as one of the ingredients (I had wondered if there was documentation
for that claim), and about two dozen patents at the end.
Sperm oil was a high
quality wax/lubricant. Its low viscosity and high
resistance to oxidation
were its high points. Its likely use was as a plasticize the binder and
surface.
There is also a lot of information in the book on
colorizing agents for plastics.
I'll put a scan up today under midwesternUniveristy, where Kreiselmaier was an asst
prof.
2:58 p.m.
On 1/4/2017 7:56 AM, allison wrote:
Sperm oil was a high quality wax/lubricant. Its low
viscosity and high
resistance to oxidation
were its high points. Its likely use was as a plasticize the binder
and surface.
As far as I know it is illegal to purchase or transfer now. Not to
possess. I have the supply my father had because he was a watchmaker.
he had bought a lifetime supply in the 40's and it is still 90% there.
But I can't transfer it.
He used a very small drop in a small dimple holder with a cap over it
for about a year. A sharp needle provided all that was placed on watch
bearings.
I'm sure it would be ideal for this application, but can only agree with
Allison about the properties of it now days.
thanks
Jim
8:10 a.m.
On Wed, 4 Jan 2017, Al Kossow wrote:
On 1/4/17 7:03 AM, Klemens Krause wrote:
...
We have a second LGP-30 drum in our museum. It is
damaged by water.
In doing some disk research recently, I came across a footnote for a rather unlikely
place to find information on magnetic coatings, which I just got a copy of:
Patton "Pigment Handbook Volume II Applications and Markets" 1973
Kurt Kreiselmaier "Pigmentation of Magnetic Tapes" pp 315-329
Nice, the book is available in our library here at the university.
I'll get it tomorrow from the magazine. :_
Klemens
--
klemens krause
Stuttgarter KompetenzZentrum fyr Minimal- & Retrocomputing.
http://computermuseum.informatik.uni-stuttgart.de
9:06 a.m.
On 01/04/2017 09:03 AM, Klemens Krause wrote:
Previous messages suggested the LGP-30 drum was plated with
nickel. If there are amateur astronomers with a vacuum
evaporator, it might be possible to get them to adjust their
setup slightly to vacuum evaporate nickel on your drum,
after refinishing the base. You'd need a rig to slowly turn
the drum while evaporating the nickel. Some other research
labs at universities might have the necessary equipment,
also - check with the Physics department (or electrical
engineering).
Jon
We both have analog recordings (from digitizing
scopes)
and logic analyzer dumps. So concerning the LGP-30, all
relevant information about the drum has been saved :-)
We have a second LGP-30 drum in our museum. It is damaged
by water.
(large rusted areas, probably from water between heads and
drum).
I'm dreaming to wash the brown oxide coating off with a
solvent like
acetone, polish the drum and repaint it.
As magnetic paint I would try iron oxide from audio tapes
solved in acetone or some other solvent.
Perhaps one could ask an airbrush artist to do this.
Rumours say, that the drums originally also were coated
"by hand".
Rewriting the timing tracks should not be impossible with
todays
electronics.
There is another guy here in germany, who has a LGP-30
with heavily
corroded drum. That would be certainly interesting for him.
10:02 a.m.
On 1/4/17 1:06 PM, Jon Elson wrote:
On 01/04/2017 09:03 AM, Klemens Krause wrote:
Previous messages suggested the LGP-30 drum was plated with nickel. If
there are amateur astronomers with a vacuum evaporator, it might be
possible to get them to adjust their setup slightly to vacuum
evaporate nickel on your drum, after refinishing the base. You'd need
a rig to slowly turn the drum while evaporating the nickel. Some other
research labs at universities might have the necessary equipment, also
- check with the Physics department (or electrical engineering).
Jon
Its very likely the plating was done using more conventional bath
electroplating.
Everything about the LGP-30 screams use of technology that was well known
and not expensive.
It in may ways resembles the PDP-8, linc, and others in the attempt to
minimize
the total hardware to get to minimal computing. Thing like FlipFlop
registers
and indirect addressing modes were left out to keep the total tube(and
diode)
logic to a minimum. A brief look at the manuals and circuits used makes it
clear to keep it small, minimize power, keep it as reliable as possible
with
tubes(valves) everything possible was left out. The 32nd bit missing (gap)
was to likely force a simple case of word end boundary (by oneshot time
out of multiple track coincidence).
From a make it run again the drum and its heads are only one pair of
issues to
be examined. The power supplies (dried out caps!) and coupling or
interstage
capacitor condition as well as general tube status plus the usual
problems with
wires and connectors including the 400 odd tube sockets.
Keep in mind that generation of machine was not so much logic level as
pulse
presence or absence to be a logical 1 or 0. So there were few places
that had
DC static states. The very next generation of tube and early transistor
machines
would have registers and static or quasi-static states.
As to the clock track its only issue is that the present electronics
does not
ever write it only reads it. So the only issue there is to use the
existing head or
a data head to write a new track and its only a matter of having enough
pulses
in the Drum rotation time and insuring the correct gaps if any. That
would be
trivial hardware to create and keep handy as it can be the very latest tech.
Allison
We both have analog recordings (from digitizing
scopes) and logic
analyzer dumps. So concerning the LGP-30, all relevant information
about the drum has been saved :-)
We have a second LGP-30 drum in our museum. It is damaged by water.
(large rusted areas, probably from water between heads and drum).
I'm dreaming to wash the brown oxide coating off with a solvent like
acetone, polish the drum and repaint it.
As magnetic paint I would try iron oxide from audio tapes solved in
acetone or some other solvent.
Perhaps one could ask an airbrush artist to do this.
Rumours say, that the drums originally also were coated "by hand".
Rewriting the timing tracks should not be impossible with todays
electronics.
There is another guy here in germany, who has a LGP-30 with heavily
corroded drum. That would be certainly interesting for him.
2:24 p.m.
On Jan 4, 2017, at 1:02 PM, allison wrote:
On 1/4/17 1:06 PM, Jon Elson wrote:
> On 01/04/2017 09:03 AM, Klemens Krause wrote:
>>
>>
>>> We both have analog recordings (from digitizing scopes) and logic analyzer
dumps. So concerning the LGP-30, all relevant information about the drum has been saved
:-)
>>>
>>
>> We have a second LGP-30 drum in our museum. It is damaged by water.
>> (large rusted areas, probably from water between heads and drum).
>> I'm dreaming to wash the brown oxide coating off with a solvent like
>> acetone, polish the drum and repaint it.
>> As magnetic paint I would try iron oxide from audio tapes solved in acetone or
some other solvent.
>> Perhaps one could ask an airbrush artist to do this.
>> Rumours say, that the drums originally also were coated "by hand".
>> Rewriting the timing tracks should not be impossible with todays
>> electronics.
>> There is another guy here in germany, who has a LGP-30 with heavily
>> corroded drum. That would be certainly interesting for him.
>>
> Previous messages suggested the LGP-30 drum was plated with nickel. If there are
amateur astronomers with a vacuum evaporator, it might be possible to get them to adjust
their setup slightly to vacuum evaporate nickel on your drum, after refinishing the base.
You'd need a rig to slowly turn the drum while evaporating the nickel. Some other
research labs at universities might have the necessary equipment, also - check with the
Physics department (or electrical engineering).
>
> Jon
I'm far from an expert, but it certainly looks like an oxide coating to me. I'm
reminded of the folklore when IBM was developing the RAMAC and finally had success with a
magnetic paint mixed up outside of house. In that case it was easy to apply...just spin up
the disc and pour!
There are a couple of 1" long spots where the coating was scraped away and the heads
relocated. Given what I've read about the Control Data badged LGP-30's, this was
likely a refurb sold in the 60's. The replacement heads certainly support that. Below
are some pics of my drum; the tonewheel clock generator can be seen at the far right. The
groove just to the left of that leaving a single band in the mag material is too perfect
to be a goof, but at the 0.4" head offset spacing, is too narrow to contain more than
one track. -C
http://www.radar58.com/temp/drum.jpg
http://www.radar58.com/temp/drum2.jpg
5:56 p.m.
On 01/04/2017 05:24 PM, Cory Heisterkamp wrote:
I'm far from an expert, but it certainly looks like an oxide coating to me. I'm
reminded of the folklore when IBM was developing the RAMAC and finally had success with a
magnetic paint mixed up outside of house. In that case it was easy to apply...just spin up
the disc and pour!
http://www.radar58.com/temp/drum.jpg
http://www.radar58.com/temp/drum2.jpg
Yup, that looks pretty "oxidey" all
right!
Jon
6:09 p.m.
On 01/04/2017 09:56 PM, Jon Elson wrote:
On 01/04/2017 05:24 PM, Cory Heisterkamp wrote:
Based on more than a few drums and disks i've seen its oxide, not plated.
I'd also say if the scratches are not deep a little polishing may be the
trick.
I'D do nothing until it can be run up (remove all dust and gunk) and
then look
at the output of the heads. Likely you don't have to write clock tracks
if there
is mechanical (tone wheel). If so that means the clock is created there
so its
always in sync with drum rotation. That's one less headache.
I have a hunch that the data/instruction tracks are not pre-recorded and
can be
over wrote and replaced at will but there is where the manuals and a
thorough
understanding of the machine and its logic is needed.
IF the data tracks are created by other timing (clock and logic) then
erasing
a track is safe (check manuals) and then you can write a track with F and 2F
and see if it reads out uniformly if it does that head is good and the
media
under it is. Step and repeat, any that fail or have to many drop outs
or other
errors need care, relocate first and try again.
This is about what old school tricks need to be found out about and
relearned.
The closest analogy is how to steam and repair a coal fired locomotive.
There
is hand me down knowledge that will be needed and learned or even
regenerated.
A very interesting project.
Allison
I'm far from an expert, but it certainly looks like an oxide coating
to me. I'm reminded of the folklore when IBM was developing the RAMAC
and finally had success with a magnetic paint mixed up outside of
house. In that case it was easy to apply...just spin up the disc and
pour!
http://www.radar58.com/temp/drum.jpg
http://www.radar58.com/temp/drum2.jpg
Yup, that looks pretty "oxidey"
all right!
Jon
5 Jan
5 Jan
12:41 a.m.
On Wed, 4 Jan 2017, Cory Heisterkamp wrote:
I'm far from an expert, but it certainly looks
like an oxide coating to
me. I'm reminded of the folklore when IBM was developing the RAMAC and
Yes, it is ferric oxide.
Hmm, your drum doesn't look to bad after all. In your case I would clean
all the heads, and the surface with a soft cloth and give it a try. For
basic testing you only need one data track plus the register and timing
tracks.
Christian
5:49 a.m.
>I would clean all the heads, and the surface with a
soft cloth and give it a try.
A place I worked, a "soft dry cloth" unless it came out of a package
made by Texwipe or their competitors was known as "sand paper", if you
were caught using such you were fired on the spot and escorted out the
building. Same for paper towels.
Just my 2c's
-pete
On Thu, Jan 5, 2017 at 1:41 AM, Christian Corti
<cc at informatik.uni-stuttgart.de> wrote:
On Wed, 4 Jan 2017, Cory Heisterkamp wrote:
I'm far from an expert, but it certainly looks like an oxide coating to
me. I'm reminded of the folklore when IBM was developing the RAMAC and
Yes, it is ferric oxide.
Hmm, your drum doesn't look to bad after all. In your case I would clean all
the heads, and the surface with a soft cloth and give it a try. For basic
testing you only need one data track plus the register and timing tracks.
Christian
8:06 a.m.
On 1/5/2017 9:49 AM, Pete Lancashire wrote:
I agree 100%. I keep shaking my head
in disbelief at these references to
paper towels and other dry forms of
sandpaper.
- J.
> I would
clean all the heads, and the surface with a soft cloth and give it a try.
A place I worked, a "soft dry cloth" unless it came out of a package
made by Texwipe or their competitors was known as "sand paper", if you
were caught using such you were fired on the spot and escorted out the
building. Same for paper towels.
Just my 2c's
-pete
12:44 a.m.
On Wed, 4 Jan 2017, Cory Heisterkamp wrote:
On Jan 4, 2017, at 1:02 PM, allison wrote:
> On 1/4/17 1:06 PM, Jon Elson wrote:
>> Previous messages suggested the LGP-30 drum
was plated with nickel.
Nope. I ever wrote about iron oxide.
I'm far from an expert, but it certainly looks like an oxide coating
to me. I'm reminded of the folklore when IBM was developing the RAMAC
Yes, I agree.
...
In that case it was easy to apply...just spin up the
disc and pour!
Good idea, this should work with the drum too.
There are a couple of 1" long spots where the
coating was scraped away and the heads relocated. Given what I've read about the
Control Data badged LGP-30's, this was likely a refurb sold in the 60's. The
replacement heads certainly support that. Below are some pics of my drum; the tonewheel
clock generator can be seen at the far right. The groove just to the left of that leaving
a single band in the mag material is too perfect to be a goof, but at the 0.4" head
offset spacing, is too narrow to contain more than one track. -C
http://www.radar58.com/temp/drum.jpg
http://www.radar58.com/temp/drum2.jpg
From the fotos your drum looks better than our working
one, with
the exception of the large engraving on the right side. Especially
the left part, were the registers are located looks very good.
On our drum are also some dark traces without showing the Al of
the drum.
I can't see the 1" long spots you're speaking from. How much is
"a couple"?
In your place I would try to revive the drum track by track:
Looking for the registers, find out if the timing tracks S1 to S3
are ok, then looking for tracks 0 to 3 in which the loader,
program 10.4 sits, then track 63, which is used for booting the
loader. Even if you have only some more tracks you can run simple
hand coded programs on your machine. Just think at a KIM-1 single
board computer with 256 bytes of RAM: People had fun with it! :-)
Cleaning the originally coated drum? I'm not sure how to do this.
We clean our RK05 disks in a very robust way: with cheap burning
spirit and paper towels. They have similar technology: Al-base
with iron oxide coating. We rubbed away thick black traces from
occasional head crashes and we never removed the oxide coating
with this torture. In every case the disks were 100% error free
after this. But in this case the risk ist low: the disks had errors
and if we ever would have washed away the oxide coating, we have
enough other disks to experiment with other solvents.
The LGP-30 drum is much more singular, so we never tried to clean
the surface to avoid the risk of cleaning away the coating.
Klemens
(p.s.: got the book, an interesting lecture)
--
klemens krause
Stuttgarter KompetenzZentrum fyr Minimal- & Retrocomputing.
http://computermuseum.informatik.uni-stuttgart.de
4:35 a.m.
On Thu, Jan 5, 2017 at 3:44 AM, Klemens Krause <
krause at informatik.uni-stuttgart.de> wrote:
From the fotos your drum looks better than our working one, with
the exception of the large engraving on the right side. Especially
the left part, were the registers are located looks very good.
On our drum are also some dark traces without showing the Al of
the drum.
That is encouraging news. The engraving on the right appears to be machined
into the drum as it's much deeper than the oxide finish and completely
uniform. I'm not sure what purpose it serves, if any. I've adjusted the 7
heads along the left side as one was just making contact.
I can't see the 1" long spots you're
speaking from. How much is
"a couple"?
There's a total of 3 such marks on the drum not visible in the photo, 2
caused at some point in the past as the heads that caused them were
relocated from those tracks, and one short scratch caused by me after
having removed all but the last head bar assembly and checking for drag. It
seems each bar had at least one, if not more, heads in contact with the
drum, which I was not expecting.
In your place I would try to revive the drum track by
track:
Looking for the registers, find out if the timing tracks S1 to S3
are ok, then looking for tracks 0 to 3 in which the loader,
program 10.4 sits, then track 63, which is used for booting the
loader. Even if you have only some more tracks you can run simple
hand coded programs on your machine. Just think at a KIM-1 single
board computer with 256 bytes of RAM: People had fun with it! :-)
I think this is a good idea. I hadn't planned on running anything other
than hand coded programs, and having at least several tracks functional
will help me in troubleshooting the rest of the machine. I can then
transition to a solid state mem later.
Cleaning the originally coated drum? I'm not sure how to do this.
We clean our RK05 disks in a very robust way: with cheap burning
spirit and paper towels. They have similar technology: Al-base
with iron oxide coating. We rubbed away thick black traces from
occasional head crashes and we never removed the oxide coating
with this torture. In every case the disks were 100% error free
after this. But in this case the risk ist low: the disks had errors
and if we ever would have washed away the oxide coating, we have
enough other disks to experiment with other solvents.
The LGP-30 drum is much more singular, so we never tried to clean
the surface to avoid the risk of cleaning away the coating.
I used a clean, soft, paper towel without any solvent or liquid and gently
ran it from left to right while rotating the drum. This picked up a little
fine oxide, but whoever serviced the drum last did an excellent job of
sealing it. After they replaced the plastic cover they ran strips of
electrical tape (which was still firmly stuck) down both sides. The air
filter is also still present on the machine which is a good sign. -C
6:15 a.m.
On Thu, Jan 5, 2017 at 3:44 AM, Klemens Krause <
krause at informatik.uni-stuttgart.de> wrote:
...
Cleaning the originally coated drum? I'm not sure how to do this.
We clean our RK05 disks in a very robust way: with cheap burning
spirit and paper towels. ...
The LGP-30 drum is much more singular, so we never tried to clean
the surface to avoid the risk of cleaning away the coating.
I've seen an IBM field service tech clean an 1311 pack once (after the drive blew a
gasket and sprayed hydraulic fluid everywhere). He used Kimwipes soaked in isopropyl
alcohol. Since this was in college, I went to the chemistry department to get high purity
(reagent grade) isopropyl alcohol for this job.
A solvent sounds good, but I would avoid "burning spirit" or rubbing alcohol or
other grocery store stuff since it probably has all manner of contaminants in it, some of
which may leave crud on the surface.
paul
6:55 a.m.
Kimwipes ! That's the brand and products I could not remember. Just one
thing to add, there are many different types/variations, so be careful.
On Jan 5, 2017 7:15 AM, "Paul Koning" <paulkoning at comcast.net> wrote:
On Thu, Jan 5, 2017 at 3:44 AM, Klemens Krause <
krause at informatik.uni-stuttgart.de> wrote:
...
Cleaning the originally coated drum? I'm not sure how to do this.
We clean our RK05 disks in a very robust way: with cheap burning
spirit and paper towels. ...
The LGP-30 drum is much more singular, so we never tried to clean
the surface to avoid the risk of cleaning away the coating.
I've seen an IBM field service tech clean an 1311 pack once (after the
drive blew a gasket and sprayed hydraulic fluid everywhere). He used
Kimwipes soaked in isopropyl alcohol. Since this was in college, I went to
the chemistry department to get high purity (reagent grade) isopropyl
alcohol for this job.
A solvent sounds good, but I would avoid "burning spirit" or rubbing
alcohol or other grocery store stuff since it probably has all manner of
contaminants in it, some of which may leave crud on the surface.
paul
4 Jan
4 Jan
10:18 a.m.
On Jan 4, 2017, at 1:06 PM, Jon Elson <elson at
pico-systems.com> wrote:
Nice idea. You'd want to check that the same filament works with nickel. Standard
mirror coating is aluminum, using a tungsten filament. Some other metals don't work
that way because the molten metal doesn't adhere to tungsten (silver is an example).
The procedure, including the filament to use, is described very nicely in "Procedures
in Experimental Physics" by John Strong. It was reprinted by Lindsay Publications,
now out of business but it might still be available. Great book, also for some other
crafts such as glass working (useful for those who want to build their own vacuum tubes).
paul
...
Previous messages suggested the LGP-30 drum was plated with nickel. If there are
amateur astronomers with a vacuum evaporator, it might be possible to get them to adjust
their setup slightly to vacuum evaporate nickel on your drum, after refinishing the base.
You'd need a rig to slowly turn the drum while evaporating the nickel. Some other
research labs at universities might have the necessary equipment, also - check with the
Physics department (or electrical engineering). 
10:48 a.m.
On Wed, Jan 4, 2017 at 12:06 PM, Jon Elson <elson at pico-systems.com> wrote:
Previous messages suggested the LGP-30 drum was plated with nickel. If
there are amateur astronomers with a vacuum evaporator, it might be
possible to get them to adjust their setup slightly to vacuum evaporate
nickel on your drum, after refinishing the base. You'd need a rig to
slowly turn the drum while evaporating the nickel. Some other research labs
at universities might have the necessary equipment, also - check with the
Physics department (or electrical engineering).
Will the desired thickness be enough with sputtering or evaporation? For
modern hard drives, sure, but my gut instinct is that you'd want a thicker
coating on the drum. I'd suggest sputtering over evaporation since it will
probably adhere to the surface better. I'd think nickel electroplating
would take less time and effort, though.
Heck, I have about 4 L of nickel plating solution as well as an anode, if
someone wants to give it a shot.
Kyle
11:30 a.m.
On 01/04/2017 11:48 AM, Kyle Owen wrote:
Will the desired thickness be enough with sputtering
or evaporation?
For modern hard drives, sure, but my gut instinct is that you'd want
a thicker coating on the drum. I'd suggest sputtering over
evaporation since it will probably adhere to the surface better. I'd
think nickel electroplating would take less time and effort, though.
Heck, I have about 4 L of nickel plating solution as well as an
anode, if someone wants to give it a shot.
Thinking more about this a bit...
"Modern" aluminum-substrate plated media uses a layer of electroless
nickel, which is then polished, then plated with a layer of electroless
cobalt. I don't know if cobalt can be vacuum-sputtered onto nickel.
Lubrication layers are often added in the case of Winchester drives.
I suspect that the LGP30 drum heads require a substantial signal, so
perhaps 5 micron cobalt plating wouldn't work. In any case, the low
recording density might be better realized through a traditional
iron-oxide-in-binder coating.
--Chuck
11:59 a.m.
On Wed, Jan 4, 2017 at 12:30 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 01/04/2017 11:48 AM, Kyle Owen wrote:
I am not a EE, but in a ignorant attempt at of the box thinking.....
Make a new drum out of AL, glue strips of COTS magnetic tape to it.
-- Charles
Will the desired thickness be enough with
sputtering or evaporation?
For modern hard drives, sure, but my gut instinct is that you'd want
a thicker coating on the drum. I'd suggest sputtering over
evaporation since it will probably adhere to the surface better. I'd
think nickel electroplating would take less time and effort, though.
Heck, I have about 4 L of nickel plating solution as well as an
anode, if someone wants to give it a shot.
Thinking more about this a bit...
"Modern" aluminum-substrate plated media uses a layer of electroless
nickel, which is then polished, then plated with a layer of electroless
cobalt. I don't know if cobalt can be vacuum-sputtered onto nickel.
Lubrication layers are often added in the case of Winchester drives.
I suspect that the LGP30 drum heads require a substantial signal, so
perhaps 5 micron cobalt plating wouldn't work. In any case, the low
recording density might be better realized through a traditional
iron-oxide-in-binder coating.
11:50 a.m.
On Jan 4, 2017, at 2:48 PM, Kyle Owen <kylevowen at
gmail.com> wrote:
On Wed, Jan 4, 2017 at 12:06 PM, Jon Elson <elson at pico-systems.com> wrote:
Electroplating sounds ok, I don't know about procedures. You'd have to be careful
that the electrolyte doesn't damage the drum body.
Evaporation and sputtering are used to make well controlled thin films, but there's
nothing I can think of that limits how long you continue. A mirror is coated only to the
point that its reflection coefficient reaches the limit of the metal used, more is not
useful. But here you could just keep going however long you need.
As for adhering, both should produce good coatings if the substrate is clean. I remember
a test for good evaporative coating technique: coat a test piece, then try to rip off the
coating with scotch tape. It shouldn't be affected at all by that test.
There are reasons for using sputtering vs. evaporation, but I don't remember them. I
think the Strong book I cited discusses the subject.
paul
Previous messages suggested the LGP-30 drum was plated with nickel. If
there are amateur astronomers with a vacuum evaporator, it might be
possible to get them to adjust their setup slightly to vacuum evaporate
nickel on your drum, after refinishing the base. You'd need a rig to
slowly turn the drum while evaporating the nickel. Some other research labs
at universities might have the necessary equipment, also - check with the
Physics department (or electrical engineering).
Will the desired thickness be enough with sputtering or evaporation? For
modern hard drives, sure, but my gut instinct is that you'd want a thicker
coating on the drum. I'd suggest sputtering over evaporation since it will
probably adhere to the surface better. I'd think nickel electroplating
would take less time and effort, though.
1:43 p.m.
On 01/04/2017 03:50 PM, Paul Koning wrote:
Several things. Getting aluminum clean and keeping it so means NO
oxygen, it develops a
oxide coating really fast. Other metal might be used but your generally
limited to non magnetic
substrates (aluminum, glass, brass, bronze).
Also the thickness of the magnetic media, rate of travel (speed relative
to the head), head
distance and gap are all interrelated. For heads of that era the gap
will be wide, the media
thick, and the rate of travel high. Those factors determine bit density
(likely very low) and
the data rate is really low as the machine is slow.
If the drum is scratched then moving heads one gap width right or left
should do fine.
Plated media doesn't help with this save for its mechanically easier to do.
Allison
On Jan 4,
2017, at 2:48 PM, Kyle Owen <kylevowen at gmail.com> wrote:
On Wed, Jan 4, 2017 at 12:06 PM, Jon Elson <elson at pico-systems.com> wrote:
Electroplating sounds ok, I don't
know about procedures. You'd have to be careful that the electrolyte doesn't
damage the drum body.
Evaporation and sputtering are used to make well controlled thin films, but there's
nothing I can think of that limits how long you continue. A mirror is coated only to the
point that its reflection coefficient reaches the limit of the metal used, more is not
useful. But here you could just keep going however long you need.
As for adhering, both should produce good coatings if the substrate is clean. I remember
a test for good evaporative coating technique: coat a test piece, then try to rip off the
coating with scotch tape. It shouldn't be affected at all by that test.
There are reasons for using sputtering vs. evaporation, but I don't remember them. I
think the Strong book I cited discusses the subject. Previous messages suggested the LGP-30 drum was
plated with nickel. If
there are amateur astronomers with a vacuum evaporator, it might be
possible to get them to adjust their setup slightly to vacuum evaporate
nickel on your drum, after refinishing the base. You'd need a rig to
slowly turn the drum while evaporating the nickel. Some other research labs
at universities might have the necessary equipment, also - check with the
Physics department (or electrical engineering).
Will the desired thickness be enough with sputtering or evaporation? For
modern hard drives, sure, but my gut instinct is that you'd want a thicker
coating on the drum. I'd suggest sputtering over evaporation since it will
probably adhere to the surface better. I'd think nickel electroplating
would take less time and effort, though. paul
2:55 a.m.
On Tue, 3 Jan 2017, Paul Koning wrote:
The key questions for reconstructing such a device is
what the
modulation scheme is, and the pulse pattern. There might be marker
pulses for sector start, for example, or that might just be derived from
a counter in the controller.
It's in the maintenance manual. There is one flux change for a one bit,
and a flux change to the opposite direction for a zero bit.
All timing is derived from the timing tracks S1..S3. The magic box to
reconstruct these timing tracks must be synchronized to the base clock
coming from the drum (137 kHz on European machines). The base clock is
picked up with a special read head, the clock bits are "engraved" into the
drum cylinder, so no need to write this clock track.
Christian
3 Jan
3 Jan
12:46 p.m.
On 01/03/2017 01:19 PM, Paul Koning wrote:
Metal alloy plating seems common in fixed head disks
also, at least
in the ones from DEC I have seen. Making a new drum sounds like a
great class project for an ambitious machine shop student.
Modern CNC gear and carbide bits should make this pretty
straightforward. One could even fit a new set of modern bearings.
--Chuck
6:30 p.m.
On 01/03/2017 01:47 PM, Brian L. Stuart wrote:
On Tue, 1/3/17, Cory Heisterkamp <coryheisterkamp
at gmail.com> wrote:
YIKES!!! Well, I think the first order of business is to
check and possibly replace the drum bearings.
Then, get a sensitive dial test indicator (I have an old
Federal with .0001" markings, and a Federal
electronic indicator that reads down to 50 uInch.) Make up
a fixture to mount it on the drum frame and see if the
surface of the drum is still true. It is possible that the
bearing inner races might need to be turned on the shaft for
minimal runout. If the surface has several wobbles per rev,
then I think the drum will not be serviceable without
turning the oxide true again. I have NO IDEA how thick the
oxide might be on these. It did seem like the G-15 oxide
was pretty thick, maybe .010" or so. If the above procedure
is for real, then it pretty much had to be, to survive such
abuse.
Doing some totally off the wall calculations in my head, I
figured out the data density would have been in the range of
100 bits/inch on the drum circumference. Calculating from
the circumference and the number of bits per track, you
should be able to calculate the bits/inch. Assuming pretty
wide gaps between the head pole pieces, and the bit density,
it should not require insanely small head flying height.
You can fairly easily get brass shim stock down to .001" or
so (kitchen aluminum foil is about .0015") to use for a head
height setter.
So, does the LGP-30 have permanent storage on the drum, or
is it erased by a magnet at every revolution?
The G-15 modeled the drum just like a mercury delay line, it
had a write head, a read head and a bar erase magnet on
every line, so there was no gap for the write head to turn
on and off between words. The FF that drove the write amp
normally recirculated the data from the read head, except
when a word was being written. Each drum track had a long
line (for program and data) and a short line. Most of the
short lines held 4 words, so they were quickly accessible.
One short line only held one word, that was the accumulator.
Jon
What I?m wondering is if anyone is familiar with
the setup/adjustment
procedure for getting the heads set correctly. There *might* be a couple of
unused tracks I can relocate heads to, but my thought is that if half a
dozen heads were already in contact, then the rest may be perilously close
as well (swelled drum?). My odds of setting 71 heads perfectly on a 50 year
old worn drum is?well?not great.
A while back I read a procedure (probably in
reference to the G-15).
Quite frankly, it scared me a little, but I'll pass it on. The idea is to
use sound. The tech would use a screwdriver as a sounding bar
between the casing and his ear. Then the head was tightened down
until you could just hear it start to brush. I don't remember for sure,
but I'd have to think that you would then back off just enough for
the brushing sound to stop. I don't recall whether the article said
that this was done with the motor running or the drum was being turned
by hand, but if it were my machine, I'd set the heads turning the drum
slowly by hand and then check for any brushing sound when the motor
comes up.
4 Jan
4 Jan
3:05 a.m.
On Tue, 3 Jan 2017, Jon Elson wrote:
So, does the LGP-30 have permanent storage on the
drum, or is it erased by a
magnet at every revolution?
Yes, the three timing tracks, and the upper half of the instruction
counter(!). The upper half containts the number of the following
sector and is used to locate the desired sector (either instruction or
data).
The G-15 modeled the drum just like a mercury delay
line, it had a write
head, a read head and a bar erase magnet on every line, so there was no gap
for the write head to turn on and off between words. The FF that drove the
write amp normally recirculated the data from the read head, except when a
word was being written. Each drum track had a long line (for program and
data) and a short line. Most of the short lines held 4 words, so they were
quickly accessible. One short line only held one word, that was the
accumulator.
The LGP-30 is similar, but the timing and long tracks (i.e. main memory)
are not recirculating. Hence the reason why a word is limited to 31 bits,
although the sector holds 32 bits. The last bit must be zero to reset the
read circuitry for the next sector.
Christian
9:01 a.m.
On 01/04/2017 06:05 AM, Christian Corti wrote:
The LGP-30 is similar, but the timing and long tracks
(i.e. main memory) are not recirculating. Hence the reason
why a word is limited to 31 bits, although the sector
holds 32 bits. The last bit must be zero to reset the read
circuitry for the next sector.
So, there is no inter-word gap to accommodate the write head
switching? I guess if everything is hard-synched to the
clock track, then you can get away without that. Interesting!
Jon
2738
days inactive
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38 comments
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participants (15)
-
aek＠bitsavers.org -
ajp166＠verizon.net -
blstuart＠bellsouth.net -
cc＠informatik.uni-stuttgart.de -
cclist＠sydex.com -
charles.unix.pro＠gmail.com -
coryheisterkamp＠gmail.com -
elson＠pico-systems.com -
js＠cimmeri.com -
jwsmail＠jwsss.com -
krause＠informatik.uni-stuttgart.de -
kylevowen＠gmail.com -
linimon＠lonesome.com -
paulkoning＠comcast.net -
pete＠petelancashire.com