28 Jan
2002
28 Jan
'02
4:26 a.m.
Another weekend project of mine has been working on a VT131
terminal. The terminal seems to work fine when receiving data.
The terminal always powers up with a "4" in the corner
(keyboard error?). Typing characters on the keyboard will give
no response from either the terminal, or the system to which
it's connected. The lights flash (all at once), and the speaker
beeps when power is applied to the terminal. No lights are ever
activated afterwards, though.
Having taken apart the keyboard, it does have an empty socket for
a DIP. Anyone know what this is?
Is it possible that this is a "lookalike" keyboard? Did DEC make
different models for different VT100 terminals -- were they
compatible? If this is an authentic DEC keyboard, will it be
marked as such somewhere? If so, how?
The key layout _looks_ like VT100, but...
The reason I'm asking about the brand is that there was another
terminal at the junk yard, completely trashed, which looked like
a VT100, but had a completely different branding. I forget the
brand right off, but I'm afraid I may have picked up the keyboard
for the dead terminal, and that it may not be compatible at all.
Failing a way to positively identify the keyboard, are there any
common modes of failure along these lines?
Also, I'm guessing at this point that the terminal is in good shape.
Does anyone know where to get a keyboard?
Chris
Christopher Smith, Perl Developer
Amdocs - Champaign, IL
/usr/bin/perl -e '
print((~"\x95\xc4\xe3"^"Just Another Perl
Hacker.")."\x08!\n");
'
28 Jan
28 Jan
4:53 a.m.
--- Christopher Smith <csmith(a)amdocs.com> wrote:
Another weekend project of mine has been working on a
VT131
terminal. The terminal seems to work fine when receiving data.
The terminal always powers up with a "4" in the corner
(keyboard error?).
Keyboard error. It's _possible_ the keyboard error is in the VT131,
but not as likely as in the keyboard. If you have a VT100 or VT101,
VT105, etc., you could test that keyboard in another terminal; but if
you just have the VT131 as your sole example of DEC keyboards, that's
a bit of a problem.
Having taken apart the keyboard, it does have an empty
socket for
a DIP. Anyone know what this is?
Have no idea. Never disassembled one.
Is it possible that this is a "lookalike"
keyboard? Did DEC make
different models for different VT100 terminals -- were they
compatible? If this is an authentic DEC keyboard, will it be
marked as such somewhere? If so, how?
If the label hasn't fallen off, ISTR that there was a paper sticker
with the Digital logo and some numbers on the bottom.
It's possible, if you can't find a vendor description anywhere, that
you picked up a keyboard for another terminal. Lots of folks used 1/4"
jacks for keyboards in those days, even Apple (on the Lisa).
The key layout _looks_ like VT100, but...
If it's a DEC keyboard, it should be compatible. I am not aware of
any major changes in keyboards, save VT100 vs LK201 and the like
(different protocol, I presume; different appearance, different connector,
etc.)
The reason I'm asking about the brand is that
there was another
terminal at the junk yard, completely trashed, which looked like
a VT100, but had a completely different branding. I forget the
brand right off, but I'm afraid I may have picked up the keyboard
for the dead terminal, and that it may not be compatible at all.
AFAIK, even though the plugs may be the same, they were not
compatible across vendors.
Failing a way to positively identify the keyboard, are
there any
common modes of failure along these lines?
Dead chip in the keyboard, usually. We never fixed them when I used
VT100s on a daily basis. We threw them into a box in the back room and
grabbed a different (working) one from stock. The fact that we were
shrinking on an annual basis meant that we never had to buy a terminal
again after we hit our peak in 1984.
Also, I'm guessing at this point that the terminal
is in good shape.
Does anyone know where to get a keyboard?
Off of a good terminal? I presume that you could find a VT100 from a
3rd party vendor. Don't know what they sell for these days.
-ethan
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29 Jan
29 Jan
12:52 a.m.
Christopher Smith wrote:
Another weekend project of mine has been working on a
VT131
terminal. The terminal seems to work fine when receiving data.
The terminal always powers up with a "4" in the corner
(keyboard error?). Typing characters on the keyboard will give
no response from either the terminal, or the system to which
it's connected. The lights flash (all at once), and the speaker
beeps when power is applied to the terminal. No lights are ever
activated afterwards, though.
Having taken apart the keyboard, it does have an empty socket for
a DIP. Anyone know what this is?
Is it possible that this is a "lookalike" keyboard? Did DEC make
different models for different VT100 terminals -- were they
compatible? If this is an authentic DEC keyboard, will it be
marked as such somewhere? If so, how?
The key layout _looks_ like VT100, but...
The reason I'm asking about the brand is that there was another
terminal at the junk yard, completely trashed, which looked like
a VT100, but had a completely different branding. I forget the
brand right off, but I'm afraid I may have picked up the keyboard
for the dead terminal, and that it may not be compatible at all.
Failing a way to positively identify the keyboard, are there any
common modes of failure along these lines?
Also, I'm guessing at this point that the terminal is in good shape.
Does anyone know where to get a keyboard?
Chris
Christopher Smith, Perl Developer
Amdocs - Champaign, IL
Jerome Fine replies:
As far as I know, ALL VT100 style keyboards are identical. As are
all LK201 keyboards for a VT220/VT320, etc. If you can find an
old dead VT100 style terminal, normally the keyboards last much
longer than the monitor portion - at least my PILE of old keyboards
is my experience.
However, there are many components inside the monitor that also
must work correctly which are concerned with receiving characters
from the keyboard and sending those characters to the
computer
(or whatever is at the end of the RS232 cable). And although they
rarely are non-functional (in most cases when a terminal goes bad
I can still send characters to the computer), I guess it can happen.
Suggestion: Get another keyboard or at least test your keyboard
in another VT100 style terminal.
OTHER KEYBOARDS from compatible VT100 terminals WILL
PROBABLY CAUSE DAMAGE to the VT131. I recommend
against doing that. If you are not sure - normally compatible terminals
are clearly marked as non-DEC, don't experiment.
Hope this helps!
6:14 a.m.
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9:03 p.m.
Um, er - my five cents...
Tony Duell wrote:
Anyway, the CRT looks to be pretty standard. 12",
90 degree deflection,
modified B7G base, 12V (or so) heater, standard pinout. I would be very
suprised if a monochrome TV tube with the same parameters (and thus
similar in other respects) couldn't be got to work here.
I seem to remember from ancient times, when I wrote a graphics "driver"
for a VT125 (ReGIS), that the screen has a somewhat nonstandard aspect
ratio. TV would have 4:3 (4 pieces wide, 3 high), while the VT1xx screen
was something like 8:5 - at least numbers that I never had come across
before. Maybe this just refers to the visible picture, and the tube is
standard though.
Yesterday evening, I dug out the microfiches, and, indeed, there is a
"VT100 Technical Manual", part no. EP-VT100-TM-001, dated "Sep 1980".
If
anything out of these two fiches can help you, we'll need to find a way
of scanning them. Reduction ratio is 42:1.
About the keyboard interface, it essentially says that this is async,
full-duplex on a single wire. The kludge is to have either end pull the
line up or down through a resistor. If you tap the center of this
voltage divider, which happens to be the actual line, and know what
level your own side is asserting, you can tell what the other side is
doing with a little OP-AMP wizardry (an analog "computor"? ;-). And,
yes, they use 12V there, so there are sufficient reasons not to connect
this to TTL directly.
The manual also says that once in each vertical period, a status byte is
sent to the keyboard to update the LEDs and to initiate a keyboard scan.
Shouldn't this be visible with a scope? - It might give a hint if the
terminal or the keyboard is broken.
--
Andreas Freiherr
Vishay Semiconductor GmbH, Heilbronn, Germany
http://www.vishay.com
30 Jan
30 Jan
8:28 a.m.
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1:19 p.m.
On Wed, 30 Jan 2002, Andreas Freiherr wrote:
Yesterday evening, I dug out the microfiches, and,
indeed, there is a
"VT100 Technical Manual", part no. EP-VT100-TM-001, dated "Sep
1980".
If anything out of these two fiches can help you, we'll need to find a
way of scanning them. Reduction ratio is 42:1.
It's not possible to scan fiche directly (or so I've been told/shown). You
first have to use a fiche printer (not cheap), then scan the paper copy. I
may end up buying a fiche printer later this year if things work out. I
had planned to buy one by mid this year, but looks like I won't be able
to.
-Toth
2:29 p.m.
New subject: IBM Punch Card Weight
This is presently on eBay:
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll
ViewItem&item=2000040030
I've deleted the thread but I hope the person who
needed it will see this. Asking a lot for a WEIGHT,
tho!
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6:50 p.m.
New subject: IBM Punch Card Weight
That one isn't the one needed for a Documentation M200 punchcard reader.
Indeed, the asking price for (basically) a flat metal plate is a lot.
Ed
Loboyko Steve wrote:
This is presently on eBay:
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll
ViewItem&item=2000040030
I've deleted the thread but I hope the person who
needed it will see this. Asking a lot for a WEIGHT,
tho!
__________________________________________________
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10:52 p.m.
New subject: Scanning Microfiche (was: VT131 needs keyboard help)
Toth,
certainly not directly with an ordinary scanner:
It's not possible to scan fiche directly (or so
I've been told/shown).
Even if you were using a true 1200dpi device, you would end up with less
than 30dpi after blowing up the image 1:42 back to it's original size.
Sure, that's not what we want.
But maybe there are devices or even companies specialized on scanning
microfiche? - How would you load this information into an electronic
archive on MO disks, for example?
Some years ago, a friend of mine managed to get a couple of frames
printed off these fiches, but the results weren't too good: poor
contrast was the main problem. If you'd scan these prints, the results
would certainly be unreadable.
--
Andreas Freiherr
Vishay Semiconductor GmbH, Heilbronn, Germany
http://www.vishay.com
31 Jan
31 Jan
2:11 a.m.
New subject: Scanning Microfiche (was: VT131 needs keyboard help)
On Thu, 31 Jan 2002, Andreas Freiherr wrote:
Even if you were using a true 1200dpi device, you
would end up with
less than 30dpi after blowing up the image 1:42 back to it's original
size. Sure, that's not what we want.
Right. The optics of the original fiche photographing machine reduce stuff
way too small to scan directly.
But maybe there are devices or even companies
specialized on scanning
microfiche? - How would you load this information into an electronic
archive on MO disks, for example?
Some years ago, a friend of mine managed to get a couple of frames
printed off these fiches, but the results weren't too good: poor
contrast was the main problem. If you'd scan these prints, the results
would certainly be unreadable.
I've researched it, but I found no affordable solution other than buying a
fiche printer. These are not small units, but still are of a manageable
size. They average about 30-40" deep, 16-24" high, and 18-24" wide. The
better quality ones (not the cheap mimeograph type you'll see in some
public libraries) use a printing system similar much like that of a laser
printer or good xerox machine. The trick to getting good output from
anything optical is keeping it *clean* and getting the image focused
properly. The average used price on a good quality unit can range from
anywhere from $500-7000. I'm looking for a production quality one more in
the $1000-2000 range, but I can't afford it right now.
-Toth
29 Jan
29 Jan
12:12 p.m.
On Tue, 29 Jan 2002, Tony Duell wrote:
On the other hand, the VT3xx terminals eat flybacks
like they're going
out of fashion. They tend to last rather less well than LK201
keyboards.
I can vouch for that. My VT340's flyback let out its magic smoke about 6-8
months ago. Does anyone happen to have the service manual and or a
replacement flyback for this thing? I'd like to repair it in the near
future. What most often causes the flyback to go out? It worked fine one
day, the next it let out a cloud of smoke.
-Toth
30 Jan
30 Jan
6:39 a.m.
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10:10 a.m.
On Wed, 30 Jan 2002, Tony Duell wrote:
This seems to match up with the behavior the terminal exhibited. I heard a
few 'plink' type sounds a few times, accompanied by 1/2 sec or shorter HV
drops. I'm guessing the flyback was starting to arc internally? This
terminal had done this off and on for a considerable amount of time...at
least a year. The flyback's case didn't crack on this one (that I noticed
anyway). I pulled it out of service the second it quit working, so that
could have something to do with it. I opened it up, and found a
considerable amount of smoke had escaped from underneath the flyback,
which would have explained the cloud and smell that prompted me to yank
the cord from the wall.
I can vouch
for that. My VT340's flyback let out its magic smoke about 6-8
months ago. Does anyone happen to have the service manual and or a
replacement flyback for this thing? I'd like to repair it in the near
future. What most often causes the flyback to go out? It worked fine one
day, the next it let out a cloud of smoke.
My experience with the VT330 and VT340 suggests that there's no other
component that fails to kill the flyback. It's just that the HV
winding in the flyback breaks down. The flyback case cracks, lots of
smoke comes out... You should check the horizontal output transistor (on
a heatsink near
the flyback) and all the diodes and capacitors round the flyback. But
most likely they're fine.
Will do. Do you have any suggestions on a replacement flyback here in the
US? I'd also like to find a service manual for this terminal, so that I
can go through the basic checks and alignment procedures once I find a
replacement.
-Toth
10:28 a.m.
Tothwolf wrote:
I'd also like to find a service manual for [a VT340], so that I
can go through the basic checks and alignment procedures once I find
a replacement.
There is a VT340-specific Pocket Service Guide (which I don't have), but
in case you find it any help, I've just uploaded the VT330 Pocket
Service Guide, EK-VT330-PS-002.
http://vt100.net/docs/vt330-ps/ (1.8MB download, PDF or TIFF)
(Nice cover page will have to wait until morning!)
- Paul
12:45 p.m.
On Thu, 31 Jan 2002, Paul Williams wrote:
Tothwolf wrote:
I've noticed a general lack of documentation on the VT340 when compared to
all the other terminals DEC made. Was the 340 just not as common? I know
it has lots of extra features not found on most of the other terminals.
Maybe it was out of most companies price range due to the "extras"?
I'd also like to find a service manual for [a VT340], so that I
can go through the basic checks and alignment procedures once I find
a replacement.
There is a VT340-specific Pocket Service Guide (which I don't have), but
in case you find it any help, I've just uploaded the VT330 Pocket
Service Guide, EK-VT330-PS-002. http://vt100.net/docs/vt330-ps/ (1.8MB download, PDF
or TIFF)
Thanks, will have a look, but I don't know how much will apply to the
VT340.
-Toth
8361
days inactive
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17 comments
10 participants
participants (10)
-
allain＠panix.com -
Andreas.Freiherr＠Vishay.com -
ard＠p850ug1.demon.co.uk -
celigne＠tinyworld.co.uk -
csmith＠amdocs.com -
erd_6502＠yahoo.com -
jhfine＠idirect.com -
quapla＠xs4all.nl -
sloboyko＠yahoo.com -
tothwolf＠concentric.net