You may rememebr that a few weeks ago I asked ofr help on the encoder of
an HP2631B printer. I've not sorted it all out, and will describe what I
did...
The initial problem was a defective 2114 RAM (!) on the procesosr board.
After replacign that, the printer rammed the carriage into the side of
the mechanmism, blowing the 2 motor driver transistors and an overvoltage
zenenr on the -20V line. Furtehr tests showd there were no signals coming
>from the shaft encoder on the carriage movement leadscrew.
I took the machine apart. Really apart. Not having the special tools to
remove the encoder form the leadscrew, I found I could take them out
together, You loosen the cap screw in the collar on the carriage motor
shafter, free the ribbon cable from the cips onthe rear paper guide, and
tkae out the 3 screws from the encoder mounting plate. The whole lot this
comes out of the right hand side of the mechamism. I could then remove
the end cover from the encoder (carring the IR emitter) and the little
cover over the cable connections.
The HP service manual warns you not t oremove the carriage rails or
platten bar, since 'an important adjustment will be upset'. I reckoned
that my pritner was in a pretty bad state already, and little could make
it any worde, so I took it all apart. I am wondering what the HP manaul
is talking about. The 2 carriage rails have their ends turned down to fit
in holes i nthe side plate, so theres no way they can be moved by more
than a few thou. And these ends are not eccentric, I checked. The platten
bar is locared by dowel pins to each side plate. It can't move either. As
far as I can see there is no problem at all with completely stripping the
mechanism. This meant I could deal with that substance well-know to all
classic computer people -- sound-deadening foam that turns to dust.
Back to the enconder. The person who said 'sounds like the IR emitter is
out' was vey close. The IR emitter was indeed not glowing. The reason was
that it's conencted to the rest of the encoder by 2 little pin sockets on
the emeltter assembly (encoder end cover) which fit onto wires coming out
of the enocderr boddy -- one of them seems to be the end of a current
limiting resistor... Anyway, one of those wires was bent and not
connecting to the emitter assembly. Easy to fix when you know where to
look!
I crelaced the shorted zneer diode on the PSU board, and did some simple
checks on the rest of the electronics. The DIP switches on the priner
logic PCB and HPIB conenctor PCB were not reliable. Since an HPIB address
swithc which doesn't set the address you expect is going to be a curse, I
replaced them. I managed to re-stake the puchbutton assemblies on the
control panel PCB -- http://www.parts.agilent.com indicates that type of
switch (plastic housing heat-staked to a PCB with gold contact pads) is
still avaialbe, but only if you return the instrument to Agilent for
repair. Sorry, but no way...
With everything back together (apart from the motor driver transistors),
it was time to give it a go. I could now see that the encoder was
producing pulses, that the end sensors worked, and that it wasn't trying
to turn on both motor driver transsitors at the same time. Powered down,
fitted the (expensive, 25A) motor driver transistors, and tried again with
the lesdscrew nut unscrewed from the carriage. The idea was that if the
motor 'ran away', it wouldn't slam the carriage into the side plate.
Tjhis time on power-up the mtoor ran -- but at a sensible speed, there
were plento of pulses from the encoder, and by just touching the
leadscrew nut I found it was indeed trying to drive the carriage to the left.
Time fore the real test. I ffittd the 3 screws holding the leadscrew nut
to the carriage, and tired again. The carriage went to the home position,
and the macjhine gave a long beep. The frontpanel buttons did nothing
apart from reset (which repeated the initialisation) and On-Line which
caused it to beep again. I tried frobbing the paper-out switch, it made
no difference, so I guessed I had a real fault.
I spend 2 hours looking at signals. The peocessor was clearly running.
The end sensor signals were fine. The enocder, position counters,
direction flip-flop, and so on all seemed to be doing the right things. I
was beginning to think i had a nasty fault in the custom HP procesosr
chip. And yet, it was running the firmware, at least enough to run the
carriage to the home position, sound the beeper, and so on. Checking what
the processor ws trying to do to the pritner logic PCB indicated it was
reading the sensors and writng to the carriage motor register, which made
sense. It wasn't randoming acccessing all the ports.
What had I missed? I went back to the paper out signal. It was high
(indicating out-of-paprr) at the input pin of the 3-state buffer on the
printer logic PCB. It was low on the motor harness pin on the PSU board
(that makes sense, there's a NOT gate on the PSU board which inverts
this sigal). But it didn't change state when I frobbed the microswitch.
Aha...
Although the microswitch is hidden inside the printer mechanism, I
managed to disconenct one of the faston terminals from it (the switch is
closed when out of paper). This time when I powered the machine up, it
homed the carriage and didn't beep. I could do linefeeds and formfeeds
>from the panel, the on-line button worked, and the self-test seemed to be
trying to print something (I'd not fitted the printhead at this stage.
So the microswtich was faulty. Strangely it was stuck closed (most switch
porblems cause them to not make contact). I removed the printer mechanism
again, turned it over, and removed the rear paper guide (4 screws). 2
mores screws released the microswitch from the guide. And it didn't
'click' when I pressed the actuating lever. Unfortunately, although it's
a standard V3 size switch, the actuator is unusual, so getting a
replacement would be nnon-trivial. With nothing to lose, I drilled out
the rivet holding the swtich together, took off the cover and remvoed the
contacts. I then fount that other substance well-known to classic
computer types -- grease that turns to cement. Cleaned it off, cleanded
thee contacts (well, while I had it apart) and resassmbled it. Now it
clicked. And an ohmmeter showet it was woring electrically too.
Put it all back together again. Now it will initialise and respond to the
control paenl -- provided there's paper in it. Time to fit the printhead
(trivial), and it now makes that well-known buzzing that everybody who's
ever been near a dot-matrix printer would recognise. Will it print
anyhting sensible? Well, let's try the ribbon. Which is jammed. The
ribbon cartridge is heat-staked together, but the hold trick of pulling htr
ribbon out and widing it back in got it free enough to work. Now the
self-test prints a character set -- and it looks quite sensible,
Tiem to try it with a computer. I grab my HPIB test set-up (HP71 + HPIL
module + HP82169 HPIL-HPIB interface) and cable it all up. Set the
printer address to 4 (yes, I used a PET in the old days...) type PRINTER
IS 4 and then PRINT. The darn thing does a formfeed (!). Then try
PRINT"0123456789". It prints "0000444488" andanotehr formfeed. Clearly
the 2 least significat bits (bits 1 and 2 in HPIB terminology) weren't
gettign through (an unconnected HPIB line is high, which corresponds to
logic 0 on this bus). Hence the CR character was becoming a formfeed...
Fortunately I'd picked an HPIB address where this wasn't a problem,
I hoped the HP custom PHI HPIB chip hadn't failed. I disconnected the
HPIB cabel from the HP82159 and removed the HPIB interface PCB together
with the connector PCB and HPIB cable from the printer/And then did
continuity checks from the free end of the HPIB cable to the pins on the
3448 buffer chips on the HPIB PCB. Fortuneately bits 1 and 2 were indeed
open.And a few morre detaild test showed it was nothing more than dirty
contacts on the H{PIB socket. A cotton bud and propn-2-ol cured that.
And then it printed properly -- at last. The last job was to fit the
cover and platten knob, which was trivial -- at least after everything else.
-tony
Does anyone out there have information on the disk subsystem of the
Fairchild/Schlumberger EXA 3000 tester? I think I've got it figured
out, but some validation would come in useful.
Thanks,
Chuck
Rik Bos wrote:
(concerning The Adventures of Fabulous Tony with the Dot Matrix Printer):
> NICE work !
I'd also like to congratulate to that successful bug hunting and squishing operation and utter my appreciation for its thorough description but...
I think that's possible to do without quoting that whole lot ;)
So long,
Arno
--
GMX DSL: Internet, Telefon und Entertainment f?r nur 19,99 EUR/mtl.!
http://portal.gmx.net/de/go/dsl02
A California Craigs List ad earlier this week caught my eye a couple
days ago and some emailing with the seller resulted in the following:
**************************************
Bear in mind that Gary was describing things and sometimes I don't get
the jargo quite right.
OK I have the info that you might like.
We have a bunch of Kaypros as mentioned and they are all the same $60
except the 16 which is $125
Kaypro- 2
Kaypro2 - 6
Kaypro4 5
Kaypro10 1
Kaypro 16- in original box with everything
Kaypro daisy wheel printer
Kaypro pc
Heathkit 89 A 2-
one with dual floppy , Heath buss, Serial IO card, fan
One with single floppy, and a CPU and memory main.
We also have one H8 some missing memory chips and much documentation.
We are asking $250 for H8 We have a printer buffer as well for that with
the manuals, cords etc. Happy to include with it.
I took some photos of the bunch of computers in the storage and will
send some to you if you wish. However, I have a crummy photo editor
and it requires a different email for each photo if I want to send them
in a small size.
Now, I am planning on listing the H8 in the next couple of weeks on
ebay unless someone is serious enough to come up and buy it. We are
closing our storage space in the next month or two and really want to
see the big computers etc translated into money..
*****************************************************
They added more info today:
*****************************************************
As for other stuff, it is a big list, I have over 100 assorted vintage
computers (No, no Altairs and only one slightly munched IMSAI front panel).
Partial list w/o S-100, Heath, Zenith, Kaypros or Osbornes:
3 each- TI99/4
2 each - TRS-80
Olivetti M15
Apple II
Apple IIC
Apple IIE
Apple Monitor
3 each - Apple Mac (Cube) SE
Apple Mac
Wyse Video Terminal
2 each - Dual 8" floppy subsystems (Lobo and similar)
NEC APC with built in color monitor and dual 8" floppies (seriously cool)
NEC APC III with dual 5" floppies and separate color monitor.
2 each - Amiga 500 systems in box
SWTPC 6800
Olivetti M-700-10
5 each - Compaq plasma lunch box
ASR-33 teletype with paper tape and stand (very clean).
Lots of old Monitors.
******************************************************
Units are being sold by a collector who has apprently been collecting
since the 2nd West Coat Computer Fair and who is doing some house cleaning
They have stated they will put them on Ebay soon but are willing to sell
direct
to interested collectors... Equipment is physically located in Ft
Bragg, CA.
contact info is "Barbara McCray" <bamccray at sonic.net>
DISCLAIMER:
FWIW, I know nothing of the seller or the equipment. She did mention
that she sells on Ebay as
"Dichroicarts". She is aware that I'm posting this info so if you're
interested, go direct!
steve
I've read some passing threads about the percom data separator.
Sounds pretty neat.
Anyone have schematic, or know the chips involved -- or can tell me how
this thing did its job?
Thanks
Keith
Nope, not gonna take it back.
In my circle of users in Brooklyn, EVERYBODY with a Model I had a doubler if they had disk drives. EVERYBODY.
I'm sure there are people on this list who didn't. Because you guys can be pretty stubborn, ornery and non-standard.
But anyone with a Model I who didn't get a doubler locked themselves out of lots of software, halved the storage capacity of their system, and had lots of trouble reading disks.
I bought my system as a 16k Level I, and upgraded it to a 4 drive 48k Level II.
Many people upgraded piecemeal. And a doubler was one of those "must have" upgrades.
That was my experience. Having worked for Stony Clove Computer Center, Spectrum Projects, Zebra Systems, Colorware and Alpha Products.
Al
Hi,
A friend of mine gave me a GatorBox CS recently. It works nicely, but the
firmware version is 1.6.1. I tried to update it to 3.0.3 with the software at
http://alfter.us/files/gatorbox/gatorbox-cs/ but when it goes to reboot into
update mode it stops with the Ethernet LED on. The same thing happens when I
try to do a software reset. A power cycle gets it unlocked but it's no longer
in update mode. Any thoughts?
Cheers,
Alexis.
Just a quick update to save a little nailbiting and head scratching -
Dave Thompson is _not_ at the phone number/address listed under his name in Bend OR. His ex-wife answered the phone and was not particularly interested in providing information on Dave or his current whereabouts - "some where in the Valley, I think..." was her answer when asked. Maybe a Priority Mailing may do better but I don't think so.
I've also contacted several former Micro C staff/contributors and basically the story seems to be that Dave pretty much walked away from the computer scene and doesn't particularly want to be "found" at this point.
My plan is to scan the full run (I've finished 37-53 and am waiting for the earlier issues to arrive). I'll post them (either on my site or somewhere else) with the notation that they will be removed on request.
This stuff is too cool to be left moldering in old boxes.
Jack
Here's an obscure one.
I need to find some manuals for the Nokia MikroMikko 3 computer from the
mid-1980s. Perhaps someone from the Scandanavian countries might be able
to assist?
Specifically, I'm looking for the "RTX II Monitor Manual User's Guide" and
the "RTX II File Management Reference Manual and User's Guide".
Originals or PDFs will do at this point.
I'm offering a negotiable bounty on this one. Let me know if you have any
and what it would cost to get either the manual or a copy.
Please contact me directly.
Thanks!
--
Sellam Ismail Vintage Computer Festival
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