Re: [midatlanticretro] Tech weekend -- everyone's projects ...
- On Mon, Jul 02, 2012 at 01:13:47PM +0000, Evan Koblentz wrote:
> Could everyone who attended send a list message about their projectsI worked on MARCH's PDP-8/E. I first removed the inappropriate modification
> from this weekend? It would be nice for everyone else to hear about
> progress made and how it was done.
of a mouse (furry model). After removing as much as possible and the
decaying foam residue I started with the
M8655 teletype control card. I put it in the 8/M I brought for testing
toggled in a simple send repeating 0-255 characters program
and it didn't work, no output. I first checked the signal to say
we want to send a character. It was a narrow spike instead of a proper
pulse. I traced that back to E52 which was only going to 2V. I'm not
positive which pin. With a 2k resistor to 5V I verified the signal
would go high. This showed it was the driver chip and not a bad input
on another chip loading down the signal. Replacing that chip, a DEC 11380
with a SP380A make it start transmitting data. The data sent was incorrect.
I modified the test program to output the pattern set on the switch
register. Next I probed from the data bus input signal until I found a signal
that was incorrect. Two of the outputs on E31, a 74175 weren't going high.
With the resistor test again I verified the signal can go high. Replacing
that chip made it better but still had errors. That chip didn't come out
easily so the board was messed up some. I lifted a pad on E31 so had to
solder on a little jumper wire to fix it. I repeated the process and found
E25, another 74175 had a bad output also. Replacing it fixed the card.
Due to having to leave earlier than planned I didn't get to do any more
more testing. The cards will need more cleaning and probably re-tinning
the worst traces from the mouse/foam mess. I didn't see any serious
damage. The backplane is in worse shape. They need better cleaning than
I could do there with proper cleaners for the residue and for the corrosion.
The case also is somewhat rusty on the inside. The foam on the top and
under the backplane was removed but not replaced. The air filter foam
also was gone and has not been replaced.
I'm not sure how much of the corrosion is mouse and how much foam. Some
of the foams are corrosive when they break down.
With 3 bad chips on the first board I would expect more bad chips on the
rest of the board. It should be able to be returned to running with a
reasonable amount more work.
The backplanes were dated 1970 and 1974. It may have been a single backplane
machine expanded later. The processor cards were M833, M8310, M8300. The M833
indicates its an early machine since it was replaced by the M8330 early in
the 8/E life. The machine also has
M837 Memory extension and time share
M8655 Teletype control (late model)
M882A Line frequency real time clock
M865 Teletype control (very early model, also later models are M8650)
M835 Positive I/O bus interface (early model, replaced by M8350)
M849 RFI shield
M8320 Bus loads
G227, G104, ?? core board (two sets) 4K core
Do you think we may want to create a how it was restored poster at some
point? If so I can collect other peoples pictures. I took them to document
where things were before I took it apart. They aren't the best for poster
purposes. I assume we don't want a picture of the actual mouse. I'm not
sure if the rest it just disgusting or interesting to the public.
I still don't have power. Did pick up the generator from my mother so I
have intermittent power. They say everybody will have power back on the 6th.
- I worked on a 1962 Burroughs B122 card reader, tagged for 3C/Honeywell
(for a DDP 116). Mostly I spent my time cleaning the thing, as it was
filthy, with some extremely stubborn tape residue on every panel. I
also visually audited the machine, and in general found it to be in
good condition. The belts are decent, and better yet, no rubber
rollers inside - only metal. I could manage to manual feed a card
through with no jams (mostly).
I did not power the machine up, as I found a bad high voltage
capacitor in the power supply. The plug on the end cap of the part is
clearly bulging out, and ready to pop. It is a 20 uF 450 VDC part, so
there were none in stock.
- --- On Mon, 7/2/12, Evan Koblentz <evan@...> wrote:
> Could everyone who attended send aI worked on the a couple of 3B2 machines. I pieced the two broken machines MARCH has into one good one. One computer had the unusual failure of having the internal motherboard supports (rubber bumpers) dissolve into a gooey liquid. Interesting to note was that neither machine had a good floppy drive. One had a broken latch mechanism, and the other had a massive burn mark on it from a failing tantalum capacitor. I combined components of the two drives to make one working drive.
> list message about their projects from this weekend? It
> would be nice for everyone else to hear about progress made
> and how it was done.
MARCH now has an operational 3B2/310 - 80mb hard drive, 4mb of RAM, running UNIX 3.2. I did not do a clean install, I wound up simply breaking the existing root password. There's nothing of interest on the machine, seems to be a fairly base install as it is. We can always do a clean load, I've got all the software. I shuffled a couple of PORTS boards (4 port serial/1 port parallel) into the good computer - the throughput on these kind of stinks, so if you ever wanted to run several terminals off this computer at once, it would behoove you to spread them out over a couple cards.
I did some disk copying, although not enough - I mostly wound up duplicating Osborne boot floppies, but I archived a good stack of the Osborne disks the club has - next time we get together, perhaps we can all take turns feeding disks for a while, it would be nice to archive the Osborne disks, as well as some of the other assorted software the club has for other computers.
I brought my 11/05, but didn't get to spend too much time troubleshooting it, but I've got a few more things I can check now.
I won second to smoke with a terminal. Evan takes the title of first to smoke with an Osborne.
I wound up spending a lot of time helping other people with stuff, and it was really a great event - I had a lot of fun. Look forward to the next time we do something like this.
- --- In firstname.lastname@example.org, "Evan Koblentz" <evan@...> wrote:
> Could everyone who attended send a list message about their projects from this weekend? It would be nice for everyone else to hear about progress made and how it was done.I came by on Sunday morning not for the Tech weekend, but just for the opportunity to hear Lee Felsenstein. Although I hadn't intended to get into the "project" mode, I ended up being utterly fascinated by what was going on. Bill Dromgoole patiently explained to me what he was doing as he dug into his Cosmac, and I got to follow along more-or-less comprehending the limited but very impressive success he achieved. And I greatly enjoyed watching Mike Loewen achieve significant progress in bringing a card punch back to life. (Vacuum tubes I "get", chips can be a little intimidating but I'm easily frightened by mechanical things!) Mike and I also got to talk a bit about the zen of keeping these types of increasingly esoteric skills alive. Ian Primus made my day by providing a fresh boot disk for my Osborne 1, which to my great delight woke right up and ran after napping for perhaps the past 20 years. Several other members also provided various other random bits of kindness.
This was the first time I've really spent any "quality time" at a MARCH gathering and I was greatly impressed. The the fact that everyone was just happy to be there doing this stuff was inspiring.
I had no idea what to expect from Lee. As a legendary figure, he could have sat on his laurels and retold old stories, or even just stood up there and read from the phone book and I'd have been glad just to meet him. But it was way inspiring to hear him talk not so much about the old days when they were making computers out of rocks and duct tape, but of what he's doing now to help enable the next generation of legendary figures. Wow, now I really respect him!
I may also be in the running for a "last to smoke" prize. As I was demonstrating the newly-revived Osborne back at home to my daughters, fielding questions like "So which version of Photoshop does it run? 1.0? Heh, heh, heh!" and "Where's the mouse?" daughter #1 suddenly yelled out "Dad, it's on Fire!" and with a fresh appreciation of how portable this computer is NOT, I hustled it out the back door. Oh well, it continued to run right up until I pulled the plug so hopefully a few caps will be the limit of the damage.
Thanks to everyone. I had a great time.
-- Dave Sica
- On Tue, 3 Jul 2012, David wrote:
> I had no idea what to expect from Lee. As a legendary figure, he could...that should be "stone knives and bearskins". :-)
> have sat on his laurels and retold old stories, or even just stood up
> there and read from the phone book and I'd have been glad just to meet
> him. But it was way inspiring to hear him talk not so much about the old
> days when they were making computers out of rocks and duct tape, but of
Mike Loewen mloewen@...
Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
- --- On Tue, 7/3/12, David <davesica@...> wrote:
> I may also be in the running for a "last to smoke" prize. AsChances are, it's the notorious little RFI filter capacitor in the power supply. These fail with frightening regularity - the particular ones used in these old computers break down with age and fail with a plume of smoke. They don't cause damage to other components when they go, and the computer will actually function without it.
> I was demonstrating the newly-revived Osborne back at home
> to my daughters, fielding questions like "So which
> version of Photoshop does it run? 1.0? Heh, heh, heh!" and
> "Where's the mouse?" daughter #1 suddenly yelled out "Dad,
> it's on Fire!" and with a fresh appreciation of how portable
> this computer is NOT, I hustled it out the back door. Oh
> well, it continued to run right up until I pulled the plug
> so hopefully a few caps will be the limit of the damage.
Basically, the capacitor goes across the AC line at the input of the power supply, and suppresses the switching noise from the supply, reducing the amount of RFI the computer generates. They're "line rated" capacitors, designed not to fail in a mode that causes them to make the chassis hot, or create another unsafe situation. You should only replace them with components of the same or greater safety rating (X2 rating is current and common).
If you open the computer and carefully inspect the power supply, you should find it easily, it will be a square yellow clearish plastic block, with a crack in it and burnt stuff coming out. It's usually a .1uf 250V X rated RIFA brand capacitor.
You should really replace the part, but simply desoldering or clipping it out will suffice. It's not critical for the operation of the computer - it's simply there to reduce the noise on the power line, to help prevent the computer from screwing with television reception and stuff like that.
- --- In email@example.com, "Evan Koblentz" <evan@...> wrote:
> Could everyone who attended send a list message about their projects from this weekend?
A work in progress, it's my description of the event and the work I was immediately involved in, or witnessed. I was simply too busy to follow everyone's work. It was, after all, a work session.
Many of the photo links are "broken" - I need to process down the photos to manageable size. I run a 20th century Web site, not a modern one. It's my particular interest, to "report" on the event.
I'll do what I can to add briefs on other people's work, Web links. I'm taking the liberty of quoting some of the self-descriptions in this thread. Those who attended, contact me privately to correct my errors and omissions (a contact email is at the bottom of my Web page.)
What did I do? I worked closely with Bill Degnan on both of our Proc Tech SOL computers. Mine came up! After decades! Bill's did not, his 8080 processor (with or without in-circuit emulator) can't seem to read or write to memory or ROM. But I did not have time to complete my repairs of the keyboard, to replace all the capacitive foam/Mylar pads. It was usable anyway, "naked".
I was prepared to add a working Northstar floppy controller but did not have a double-sided drive (or time) to try out Bill Sudbrink's SOL/N* disks - thanks for a copy of those.
PT co-designer Lee Felsenstein looked over our shoulder to verify the operation of the divide-by-seven circuit that feeds the 8080 with a 2MHz clock from a 14MHz crystal. He read the schematic and worked it out in front of me & Bill. He's "still running on all cylinders" as we old-guys say. He had something to say about making more engineers, later in the afternoon.
I also cleaned up my PDP-8/F, which was not nearly as "dusty" as the MARCH PDP-8. David inspected my system and commented. BTW, his work on debugging the MARCH 8's serial port was simply amazing field service. It was fun to watch him clean the club's 8.
Oh - when the A/C timed out, I reset the controls, and figured out that no one had opened all the A/C vents in the room. Brilliant. I, and many others, noted the lack of grounded outlets in the room - namely, ONE, plus one in an adjacent room. *Evan, take note.*
Otherwise, I took photos and ate pizza, and asked hard questions. I'm pleased with how it went.
- --- In firstname.lastname@example.org, "David" <davesica@...> wrote:
> Ian Primus made my day by providing a fresh boot disk for my Osborne 1, which to my great delight woke right up and ran after napping for perhaps the past 20 years.A mistake many people make, and made during the event, was to run the Osborne without opening the vent. It will cook itself. Open the vent.
> I may also be in the running for a "last to smoke" prize. As I was demonstrating the newly-revived Osborne back at home to my daughters, daughter #1 suddenly yelled out "Dad, it's on Fire!"
Otherwise, various caps will short and smoke. Find them as soon as possible after ignition. Then tag 'em so you can repair them later. Wait a day, a week, and you will lose the smell of it, it will stink up the rest of the machine.
>> A mistake many people make, and made during the event, was to run the Osborne without opening the vent. It will cook itself. Open the vent. Otherwise, various caps will short and smoke.Lesson learned! Will keep the vent open on the museum display unit. Thanks for showing me that -- I didn't know there was a vent. I thought that was some kind of service panel.