test-drb

test-drb@ccmp.vtda.org

101090 discussions

by quapla＠xs4all.nl

Picked something interesting up a few days ago, a graphical system which used to be part of a spectrum analyzer. It's a PDP-11/23+ with a graphics option, a monitor, joystick, an interface box for the keyboard, an Ampex diskdrive which uses packs and has a fixed disk inside and a Printronix lineprinter with 4 spare ribbons ((these are big, abouth an inch or so wide) It comes with XXDP+ (no idea which version yet), a library disk, a disk with RSX11M+ V3.0D and a stack of 30 extra data disks. Fortunately, the system docu is there, both for the machine, drive and printer. First thing to do is to hook up an RL02 to copy the sw over. The drive is an SMD type disk, it is controlled by an Emulex SC02 interface. Im not going to use this drive a lot, so if there are people who wants to take some of these data packs, you're welcome to get some. Ed

19 years, 6 months

What to do with a VAX KA655 board that is prone to CDAL parity error?

by vax9000＠gmail.com

It looks clean and great, but it reports CDAL parity error (machine check 10) randomly if the panel head is installed in place, when it is processing bulk of data. If the panal head is hanging there loosely, the chance of getting a CDAL parity error is much much rarer. What could cause this problem? A defective cache memory chip? supportive TTL chip? capacitors? Or is it better for me to unsolder the CPU and sell it to collectors? Any idea? vax, 9000

19 years, 6 months

HP 2000F'

by rickb＠bensene.com

>The consensus was that we did "HEL" to login and that the accounts >were <alpha><digit><digit><digit>, in particular X999 was the games >account. (That rang a memory chord with me when it was mentioned.) >It was also remembered that A000 was the "root" account on the >machine. The login was of the form HEL-XYYY,<password> for the earlier systems, and later, HEL-XYYY,<password>,<terminal identifier>. The password was usually a combination of non-printing control characters to avoid the password showing up on the teletype printout. X was a letter from A through Z. YYY was 000 through 999. If the last two digits of YYY were 00, then the account was a "group" account, which was available to all members of that group as a library account, for shared files/programs. A000 was indeed the "root" account, which did have access to a few extra commands. Z999 was also an interesting account --- it was the "system overhead" account. All available "free" disk space was available to this account. In 2000C and C' systems, there was a "beature" (a cross between a bug and a feature) where if the "NAM" (name a program) command was issued with an argument of ",", e.g., "NAM-,", the user would get "dropped" into the Z999 account with no password request. It's unclear if this was a "back door" for HP service personnel, or if it was a bug, but it was explicitly noted in the user's manual for the system that "," was an invalid argument to the NAM command. "NAM-," would simply be acknowledged by the TSB system sending a linefeed, indicating that the command had been processed. At this point, it was possible for a user to "crash" the system by asking it to create a file that was so large that it consumed the remainder of free disk space. The timeshare system could also be "locked up" for varying periods of time by creating large files. In TSB, data files had to be pre-allocated to a given size, and all of the blocks were "claimed" as part of the creation process. For example, doing a "CRE-FILE,10000" would create a 10,000 block file. Normal user accounts were limited to perhaps 100 to 200 blocks of storage. Creating a 10,000 block file took the system quite a long time, and during that time, all timesharing operations would cease while the system was locked in "system state", creating the file. This was discovered by a friend and myself in high school. It was quite interesting the first time we tried "NAM-,", simply because the manual said it was invalid, and were quite surprised when the system just accepted the command, but didn't appear to do anything. We then typed "CAT" (shows disk catalog), and it showed an empty directory, with a large number of available blocks. We tried "CRE-FILE,1000" at first, and when we hit RETURN, we noted that there was a period of time where the other three teletypes which were active in our high school computer center stopped typing, or even echoing input, until our command completed, then everything resumed where it left off. We deleted FILE, and then tried CRE-FILE,10000, and the other terminals stopped...dead in their tracks, for a few minutes (most people thought the system had crashed, and turned off their teletypes) while the system was creating this large file. We then did a PUR-FILE (PURge - deleting the file), which again locked things up (for a period of less time) while the system was deleting the file. We then did a "CRE-FILE,1000000", which was in excess of the number of blocks that the "CAT" (CATalog) command showed, and the system "went away", and the computer math teacher soon got a call from the data center saying that the system had crashed for unknown reasons, and that it would be some time before it would come back. We had quite a bit of fun writing little programs which would wait for a specific time (during other people's classes), and then "crash" the system at that time. Eventually, we got caught. We didn't get into too much trouble. How they tracked us down, I'm not sure, but I believe that through the crash dumps that the system generated when it crashed, HP engineers were able to figure out which async mux line was causing the problem, and then tracked it back to our school. A patch was put in place that fixed the problem, resulting in an "ILLEGAL FORMAT" error if NAM-, was entered. This fix was incorporated into all later releases of HP 2000 TSB, including HP 2000F, HP 2000F', and HP 2000/Access. I sure loved these systems. They were wonderful systems to learning the basics of computing through. They weren't as fully featured or flexible as competitor Digital Equipment's RSTS/E timeshare systems (I have other fun stories to tell about finding bugs in RSTS/E), but they HP system were really a lot of fun, especially 2000/Access, which added a lot of neat functions. I'm really happy that Jay has managed to find the various special bits (microcode and mux hardware) that makes it possible to have an operational HP Timeshared BASIC system running as "the real thing". Rick Bensene The Old Calculator Web Museum http://oldcalculatormuseum.com

19 years, 6 months

Help With an Erastz-11 DLL

by jhfinedp3k＠compsys.to

Can anyone help me with a simple link to an assembler / linker for a Pentium III / Pentium 4? I am attempting to use the EMEM.DLL (Emulated PDP-11 Memory) under Ersatz-11, but I am basically a dummy when it comes to using X86 code, especially finding a pair of suitable assembler / linker programs. I downloaded the Watfor programs, wasm.exe and wlink.exe, but I am not able to assemble the original file, EMEM.ASM at this point. In case anyone is interested, the EMEM.DLL under E11 provides access to PC RAM via emulated PDP-11 hardware registers. The current version which I have been using allows up to 8 MBytes, but I want to increase that to about 600 MBytes so that I can write a faster sieve program for Prime Numbers which looks like it runs in a PDP-11. If I can get the test version to run fast enough on a Pentium III, I will try it on a Pentium 4 with 4 GBytes of memory and see if it is possible to sieve the primes up to 10**18 (essentially a 64 bit sieve program) in a reasonable time (i.e. less than 1 year!). Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.

19 years, 6 months

SPAM (on list) was:Re: classiccmp list (sort of) help requested

by sdc695＠yahoo.com

The growing problem with SPAM, etc.. It was noted in one of the trade publications I looked at that a very effective check on SPAM was to confirm that the stream opened up to you (on your port 25) actually did a "conversation" with the remote player. It seems that the 'bots just open up port 25 and send (spew), and ignore the responses. Kinda like 'typeahead'. If you can sense this, it quashes some stuff (so I've been told). Another tact might be to see if the sender HAS a port 25 on their machine. I suspect that the 'bot machines don't. Just a couple of ideas. Unfortunately fixes like these require a deep diving into the SMTP mailer at the code level. ob. on topic.. Sendmail is over 10 years old (maybe that is the problem!) -- Tom Watson tsw at johana.com ____________________________________________________________________________________ Have a burning question? Go to www.Answers.yahoo.com and get answers from real people who know.

19 years, 6 months

Searching for some PDP-11/23-PLUS items

by spedraja＠ono.com

Hi. I could finally get some time to put in working state my PDP-11/23-PLUS. Once I could check the correct startup of the system, I should like to obtain these items that detail below: * Original rack for this system, with its 874 power controller, backpanels and rack inner metal rails. * Cable kit for one RLV12 (RL02 controller board), at least for two RL's * TSV05 (Pertec) cable kit. I have the tape unit and the board but no cables * -YA terminator for one BA11-S expansion box. I have the main BA11-S plus another one to extend the system, plus both connection boards (plus cables) for the boxes, but the PDP-11/23-PLUS manuals speak about another terminator board. I only remember now the final part number letters (-YA). Other items are welcome, but I suppose it would be more difficult their transport. I am mostly interested in one or a couple of working RL02. If someone can get rid of some of this, or even sell it for a reasonable price, contact me off list. I live in Europe, by the way. All indications and suggestions about these matters are welcome too. Greetings Sergio

19 years, 6 months

Advice for tape drive repair / maintenance

by jtp＠chinalake.com

A number of years ago I had some luck making rollers using two methods: (1) Use a double punch to punch out thin doughnuts of rubber--too thick deforms on punch. Stack them on the shaft tacking them with a very small amount of silicon or urethane glue. Mount in chuck of drill press and turn slowly against stones of different coarsenesses to smooth the surface. You may need to fiddle with the speed to get a good finish. This method usually requires that you can somehow cap the top and bottom of the roller, especially if the doughnut is wide. (2) Cast a new roller using urethane or silicon. Mount the shaft, or tube that represents the inner diameter, in a drill press. Using an n-way machining vise, center the outer tube with the inner shaft. Pour in goo, lower inner shaft into goo using the press handle and fine tune the positioning with the vise if needed. I turn the shaft a few times to get the goo the settle and air to vacate. Let harden, remove with plunger, heat or cold. Trim as needed. For outer casings, I've used pvc and copper tubes, but the smoothest results are with a machined and polished steel tube, open at the bottom to help push the roller out. For one roller that would not stick to the shaft, I milled several grooves in the shaft and repoured. This kept the rubber from turning. -jim

19 years, 6 months

Altair Tape MP3 test

by grant＠stockly.com

My 88-ACR is currently "bare". Can anyone with an Altair try playing this tape image? I'm using a Sony stereo cassette deck with dc servo controlled motors. I'm trying to get the best copy of these tapes that I can. I want to start a free library of actual audio cassette recordings. I guess once these recordings have been "verified", we can regenerate perfect sound images by recording the direct output of the 88-ACR. Until then... :) The only thing I am worried about is the Dolby NR (filter) was enabled. I'm not sure if this is bad or not. I have not adjusted any dynamics yet. You may have to turn up the volume... If the MP3 is not good enough, I have the raw 32bit 44100Hz available... (30MB RAR'd) http://www.altairkit.com/software/ This is what is on the tape: ALTAIR 8K BASIC VERSION 4.0 MARCH 1977 COPYRIGHT 1976 BY MITS INC. 2400/1850 HZ Grant NOTE TO ARCHIVE: This file may not exist forever, it is a beta file. : ) Look for other posts. : )

19 years, 6 months

TI Travelmate LT220 portable terminal w/inkjet printer dock

by legalize＠xmission.com

I just picked up an interesting portable terminal from ebay for $0.99 I guess there aren't really any other terminal collectors out there! Anyway, this is a nice little unit. 80x24 LCD screen, NiCad battery pack for portable operation, wall wart for AC operation. However, what's interesting about this puppy is that it has a docking station that contains an inkjet printer and a numeric keypad for data entry. The manufacturing label indicates manufacture in 1989. The terminal is VT220 compatible. There is a handle on the docking station so that you can carry the printer+terminal combination around. The whole bundle comes in a special TI black cloth bag that lets you lug it around to various locations. I have another terminal that is similar to this, but isn't as fancy with the printer dock: the Random Colleague. I purchased two Random Colleagues in a dovebid auction. One had a damaged case and the other had a damaged LCD screen. I've swapped the good screen into the good case and now I just need a little digikey ordering to connect the ribbon cable for the screen back up to the main board. The Random Colleague has a hard briefcase like case that lets you take it to various locations. Anyone else out there have either of these? -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>

19 years, 6 months

Build your own Apollo Guidance Computer

by Billy.Pettit＠wdc.com

Brent Hilpert wrote: I have a web page (<http://www.cs.ubc.ca/~hilpert/e/gates/index.html>) where I'm accumulating the diversity of symbols that have been used for logic gates. If you have a scan or reference for the Cray/6600 symbols I'd be interested in adding them. --------------------------- I'll be glad to if I can find one over Christmas. I'm flying to the Bay area on Saturday, so I'll look next week. I know I have the plastic drawing guides for the 1604, 3000 and 6000 logic symbols. And I think I have some scans of the legends of several schematics I'll send you. But my all time favorite was the logic drawings of the Bendix G-15. They were drawn by an artist. Every page is clean, neat and easy to read. Lots of comments. I still think they are the prettiest schematics ever produced in the industry. Even if it was a valve (vacuum tube) machine. The ugliest, hands down winner, are the IBM early machine drawing schematics or logic manuals for the System 360. They were done by a badly timed line printer with an exceptonally bad ribbon. Billy

19 years, 6 months

Storage Buildings

by Doug＠seadec.com

can someone please tell me how to unsubscribe from this list?? Help!! ________________________________ From: cctalk-bounces at classiccmp.org on behalf of James B. DiGriz Sent: Tue 12/19/2006 7:59 PM To: cctalk at classiccmp.org Subject: Re: Storage Buildings On Tue, 19 Dec 2006 12:14:34 -0800 (PST) "Zane H. Healy" <healyzh at aracnet.com> wrote: > Or there is always the option of getting old Freight containers (the > type they use on cargo ships). > > Zane > They're cheap enough (as low as $200 or so), and the port is only 20 miles away. FOB only, though. You need to have a flatbed or hire one, which adds to the expense. There is one unit right next door that might conceivably become available. There is another problem, though, as containers tend to receive undue attention from the vigilant eye of code enforcement here, unlike some other enlightened areas of the country, particularly if you attempt to build any kind of actual structure out of them. In my case I would have to. Freight containers are not really big enough for decent shop facilities. jbdigriz

19 years, 6 months

Any list members in Sydney, Australia?

by ethan.dicks＠gmail.com

I'm in Sydney for the week, departing Christmas Day (Newtonsday ;-) and was curious if there were any members of the list who are close enough to the Sydney CBD to warrant getting together for a beer and some classic computer conversation. I'm paying for wireless by the hour here :-/ so it would probably be better to call my mobile at 0420755794 if interested. I'm back to NZ for a few days next week, then finally back home to Ohio where I can a) look for work, and b) spend some indoor time getting various projects to a state of completion before the weather turns nice, eventually. Cheers, -ethan

19 years, 6 months

Build your own Apollo Guidance Computer (pics of actual)

by billdeg＠degnanco.com

Here are pics of the actual Apollo guidance module http://vintagecomputer.net/vcf3/apollo_guidence_module_a.jpg http://vintagecomputer.net/vcf3/apollo_guidence_modules.jpg http://vintagecomputer.net/vcf3/apollo_guidence_modules_b.jpg Bill D

19 years, 6 months

Build your own Apollo Guidance Computer

by Billy.Pettit＠wdc.com

Jeff Walther wrote Is there a guide somewhere to the different families of logic, such as RTL, TTL, LSTTL (never heard of that one) and CMOS? Try this one: http://www.interfacebus.com/Design_Logic_Family_Selection.html It's a little general but gives a good high level view. Billy

19 years, 6 months

Interesting decompiler

by Billy.Pettit＠wdc.com

On Sat, 2006-12-16 at 13:35 -0500, Dave McGuire wrote: > On Dec 15, 2006, at 10:18 PM, Chris M wrote: > > Is it a *recent* development of compilers that as an > > intermediate step the source code will first be > > reduced to assembler mnemonics, before being reduced > > to object code? > > Absolutely not. The UNIX world, at least, has been doing it that > way for decades. Right. Also, from the micro world, two words: Small C. I love the approach. Among other benefits, it allows one to write something in C to get the algorithm correct, and then re-write and/or optimize the generated assembly to speed up inner loops, and frequently executed code, as needed. Peace, Warren E. Wolfe ---------------------------------------------------------------------------- -------------- Most of the early compilers at CDC worked this way. The intermediate language was assembly and could be used to clean up the final code. It could be saved as a separate file and also be used as sub-routines. It was a very fast way to create a compiler. Then there was another method called interpreters, where final machine code never really exists. The compiler generates a list of psuedo ops that would be executed by a series of macros. Was fast to write, but incredibly ineffecient. And there was a really fascinating one on the IBM 1401 that kept the high level langauage in the core, and brought in sequential routines from the tape unit. Each rountine would perform one process on the source. At the end, what remained in core was the machine language program. It was a true single pass compiler. But it worked in serial mode, bringing in each routine in order (63 different ones, if I remember correctly) even if wasn't needed. It was probably the slowest compiler I ever worked with, but the concept was interesting. Billy

19 years, 6 months

Advice for tape drive repair / maintenance

by aliensrcooluk＠yahoo.co.uk

--- Tony Duell <ard at p850ug1.demon.co.uk> wrote: **>> snip <<** > > Well, let's see... > > I can either spend $10 on a set of rubber parts an d > take an afternoon > putting them in (at which point, said VCR will be > good for another 2 > years) or I can spend $89 and take an afternoon > going to the shop, > bringing a new unit home, and figuring out how to > connect it up and use > it. At which point I have a device assembled with > lead-free solder, > soldered at too low a temperature, so it gets dry > joints within a few > months. With plastic mechanical parts made from th e > cheapest plastic > imaginable that make a freebie toy look solid. I'd > be lucky if that $89 > machine lasted for a couple of weeks after the > warrenty period... > > Now guess which I am going to do... > > -tony > That's a very good point. Just out of interest, my dad still has the first VCR VHS recorder he bought around 1979 (no typo). It's very heavy, largely due to the fact that it's all mechanisms and levers inside. (No I don't have the model name/number at hand - I believe it's been put in the attic) It was working fine up until around 1998/9 when it wouldn't record very well anymore. i believe that's when we got our first modern VHS recorder. The new one lasted 3 or 4 years before it started playing up (won't rewind tape without messing it up, but plays/records fine!) and my parents got another one. The one my brother bought around 2001 works ok, but is hardly used. Regards, Andrew D. Burton aliensrcooluk at yahoo.co.uk

19 years, 6 months

I8008 / Scelbal

by jos.mar＠bluewin.ch

Those interested in running Scelbal, the old Basic for the Scelbi-8 8008 based system, can download the following file :( windows executable, ca 6.5 M ) http://mypage.bluewin.ch/dreesen/I8008.zip It is an emulation of a 8008 machine I might build, (Time Permitting...), and comes with very a very terse help in the form of the "scelbal.txt" file. This tells you how to start Scelbal. The emulator is rather crude, but was only intended as a proof of concept. Some source code is provided. Looking through the Scelbal source code really shows you how limited the i8008 is. You need 8K to implement a Basic that is on a par with a 4K TRS80 Basic... You are forever shuffling around pointers, incrementing and decrementing them "by hand" . Jos Dreesen

19 years, 6 months

Storage Buildings

by legalize＠xmission.com

Since I was asked, "Henk's building" I was referring to can be found by going to <http://www.pdp-11.nl/> and selecting "the making of..." link in the left frame. -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>

19 years, 6 months

KRQ50/RRD40 problems

by bob＠jfcl.com

>Probably not a lot of help, but if that interface is the same physically >as the DA15 connector on other Philips/LMS CD-ROMs, I have the service >manual for the CDD462. It's little more than a schematic and an >incomplete parts list (the CDD462 is based on an audio CD-player, and >you're expected to have the service manual for that!), but it would >contain the interface pinout. Let me know if you want me to dig it out. Maybe - I don't suppose it describes any DIP switches on the back of the drive? The actual drive in the RRD40 is a Laser Magnetics CM 201, so it's unlikely that they'd be the same, but you never know. I ask because I happened to find this article http://h71000.www7.hp.com/wizard/wiz_3914.html The wizard describes the RRD40-DC as a "slave drive" for use with an existing KRQ50/RRD40 pair. Question - what's the difference between a RRD40-DC and the RRD40-HC? Is there a switch or jumper in the drive that makes it a "slave"? Ah, if only I had a manual :-) Bob

19 years, 6 months

WPS Files into Modern Wordprocessor

by djg＠pdp8.net

>>If you wanted to convert from WPS-8 to WordPerfect, then I >>could offer my code at http://srv.net/~kth . > FYI: I got connection refused just now when trying to access your site. I modified your software to convert 8" WPS floppies dumped with my dump/restore programs and should still work with 5 1/4 dumped with putr. The conversion to word actually worked the best. It really converts to wordperfect but when going through the word converter it uses some later version codes to do better formatting. ftp://ftp.pdp8.net/software/wps/ ftp://ftp.pdp8.net/software/dumprest/

19 years, 6 months

HP 2000F'

by legalize＠xmission.com

OK, after asking around my colleagues from the day, we're narrowing in on the conclusion that it was most likely an HP 2000F or 200F'. How rare are these puppies? -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>

19 years, 6 months

LA50 ink cartridges

by legalize＠xmission.com

Item #270070599391 on ebay I've bought from this guy before and always been satisfied. He even went out of his way to replace some items for me that were damaged during shipment. -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>

19 years, 6 months

Advice for tape drive repair / maintenance

by aek＠bitsavers.org

> About 1/4 into the tape something started vibrating, quickly > escalating and before I could do anything, the tape stopped. Result: > rubber goo on the plastic roller that drives the DC-600 cartridge > drive belt, some on the tape itself, and the tape shows deformation > (wavy) on the top half. I had to toss it. This is the classic failure mode for the rollers. Pressure/Temperature causing breakdown of the rubber. > Any idea what could have caused this and how to prevent it? There is no way to prevent it. The rubber had already decomposed, and the elevated temperature caused what was left of the bonds to change state. > The other option is to remove the melted rubber roller and > steal the one from the Archive drive. They aren't interchangeable. The only option you have is to find a newer drive with a roller that hasn't decomposed (yet..). I know of no commercial source for just the rollers for either Archive or Wangtek. Wangtek changed their roller design on later drives. Archive didn't, so you may be able to find 150meg drives that are new enough to survive. The most common source are Sun external 150meg shoeboxes, which have been readily available in the past.

19 years, 6 months

Interesting decompiler

by jfoust＠threedee.com

This tool turns Borland Turbo C 2.0x .EXE back into C code: http://www.debugmode.com/dcompile/disc.htm - John

19 years, 6 months

Advice for tape drive repair / maintenance

by technobug＠comcast.net

Around Mon, 18 Dec 2006 23:21:23 +0000 (GMT), > ard at p850ug1.demon.co.uk (Tony Duell) wrote: >> The drive itself: the rubber roller driving the aforementioned >> plastic >> roller had melted. Clearly visible is the area where the rubber meets > > [...] > Baiscailly you have to replace the roller. Replacements that have been > successfully used (depending on the machine, etc) include silcone > rubber > O-rings (possibly with a grobe machined in the original hub, or a > new hub > made), heatshrink sleeving, silicoe rubber tubing (fuel line for > glow-plug engines, for example), etc. > > I've wondered if the 2-pack elastomer materials sold by e.g. Devcon > would > work. Make up a mould and cast a new roller. A lot of work, but if it > does the job well it'd be worth it in some cases. I've had extremely good luck using Plasti Dip <http:// www.plastidip.com/industrial/plastidip.html> to repair capstans. The product lays up in layers of 2-8 mils (depending on dilution) and produces an extremely uniform coating. I have repaired several HP tape decks out of 30 year old test equipment which required a layer of 70 mils. The worst runout was less than 1/2 mil. The material appear to be sufficiently durable for the task. The only drawback is the requirement for patience - each layer requires 30 min. minimum drying time. After a bit of experimentation I found that floating a bit of solvent on the surface maintained the coating consistency from dip to dip. >> For those of us with machine tools, I wonder if a roller can be "fine >> tuned" to the proper diameter by fitting an oversize piece of >> neoprene tubing to the roller, cooling the whole affair in dry ice, >> then machining it (on a lathe) to the proper size. I can't recall >> > > I believe it can, although cooling to liquid nitrogen temperatures is > recomend (if only beacuase it takes longer to warm up again, so you > have > longer to take a cut). > > I've also heard you _can_ machine 'rubbers' at room temperature, > but that > the tools are totally different from those used for metal turning. > May be > worth investigarting. > > I've not tried either though. > > -tony Cooling to LN2 temperatures has its drawbacks: the rubber either separates from the mandrel or it shatters - or both... The rubber becomes glass-like and you cannot use cutting tools to machine. A number of years back back in grad school I attempted to repair a roller for a Van de Graaff generator using LN2 and failed miserably. An old machinist got his chuckles watching my many tries. He took a CO2 fire extinquisher to cool the roller and used a grinder mounted on the lathe to surface the beast. You have to warm the object up every so often to find out what the dimensions really are. I've since surfaced a laser printer's pickup roller using a Dremel grinder mounted on my mini-lathe at room temperature with good results (didn't help one bit in the printer - those rollers are not just rough, but have a directional nap). CRC

19 years, 6 months

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