24 Dec
2017
24 Dec
'17
7:09 a.m.
From: Mattis Lind
Unfortunately I am not having any lutfisk this year.
The rest of the
family is not very fond of it.
I"m glad to see there are _some_ non-crazy people there! :-)
Anway, I can way top that - the tradition Bermudian Christmas dish is cassava
pie: make that wrong (starting with raw cassava root), and it will _kill_
you! :-)
(Cassava root contains a cyanide precursor. That's what cassava root is
banned for human consumption in Japan. Somewhat ironic, the land of 'fugu'
banning it! :-)
Noel
26 Dec
26 Dec
6:25 a.m.
2017-12-24 13:09 GMT+01:00 Noel Chiappa via cctalk <cctalk at classiccmp.org>:
After too much christmas food I spent some more time in the garage fixing
the VT50/Vt52.
The tip from Josh about the PROM socket was a good one. Replacing those
together with the two ITT made 7400 chips I already replaced there were
nice click sound when pressing the keys on the keyboard. Setting the
terminal mode to OFF-line so that it loop-backed the serial signal gave a
some kind of pattern on the video signal. But was it an OK signal or were
there any more problems in the data path? Hard to tell without reassembling
the entire terminal. But if the there actually are more faults in there I
had to disassemble it again, fix and repeat. Instead I came up with a small
circuit (well stole actually from the VT100 schematics) that generated a
composite video signal from the TTL signals generated by the VT52 and feed
it into an old Philips CM8533 monitor.
https://drive.google.com/open?id=1nMq_N8tOcIauRmfHsVKMUJ_AUymoFiu7
Yes! All the logic seems to work just fine. So now I can quite confidently
reassemble the thing and test the last step. HV generation, Horizontal
deflection and CRT.
Since the terminal appears to work I also dumped the firmware out of the
four bipolar PROMs.
http://storage.datormuseum.se/u/96935524/Datormusuem/VT52/124A9.HEX
http://storage.datormuseum.se/u/96935524/Datormusuem/VT52/125A9.HEX
http://storage.datormuseum.se/u/96935524/Datormusuem/VT52/126A9.HEX
http://storage.datormuseum.se/u/96935524/Datormusuem/VT52/127A9.HEX
@Fritz: You don't need to get a dump of the PROMs in your terminal. I think
the ones I have is in pretty good shape.
From: Mattis
Lind
Unfortunately I am not having any lutfisk this
year. The rest of the
family is not very fond of it.
I"m glad to see there are _some_ non-crazy people there! :-)
Anway, I can way top that - the tradition Bermudian Christmas dish is
cassava
pie: make that wrong (starting with raw cassava root), and it will _kill_
you! :-)
(Cassava root contains a cyanide precursor. That's what cassava root is
banned for human consumption in Japan. Somewhat ironic, the land of 'fugu'
banning it! :-)
Noel
BTW. Comparing the VT52 and the HP2640 I worked on previously is like
comparing a Skoda with a Mercedes or something. Single layer circuit board
made of some cheap material (pertinax?) versus double sided gold plated
boards. Very simple quite hardwired architecture versus generic
microprocessor based design with a back plane bus. Was it just that DEC
wanted to be as cheap as possible? The predecessor VT05 had four standard
quad sized boards in a small backplane.
/Mattis
4:25 p.m.
On Dec 26, 2017, at 3:25 AM, Mattis Lind via cctalk
<cctalk at classiccmp.org> wrote:
? Instead I came up with a small
circuit (well stole actually from the VT100 schematics) that generated a
composite video signal from the TTL signals generated by the VT52?
Oh ? this is a cool idea! Will keep in the bag of tricks if necessary for future work on
the VT52.
@Fritz: You don't need to get a dump of the PROMs
in your terminal. I think
the ones I have is in pretty good shape.
You beat me to it! I think I will still upgrade my PROM sockets over this holiday break,
and will just go ahead and dump the PROMs while I?m at it since I?ll have them out anyway.
Mine are labeled the same as the ones you listed.
cheers,
?FritzM.
5:22 p.m.
2017-12-26 22:25 GMT+01:00 Fritz Mueller via cctalk <cctalk at classiccmp.org>:
Good idea! It is always good to check so that they match in case I got the
dump wrong.
Before putting everything together I also dumped the chargen ROM board:
http://storage.datormuseum.se/u/96935524/Datormusuem/VT52/23002B4.HEX
Since it is dumped at the outputs of the board it is AFTER the set of
inverting 7404s used on the chargen board.
/Mattis
On Dec 26,
2017, at 3:25 AM, Mattis Lind via cctalk <
cctalk at classiccmp.org> wrote:
? Instead I came up with a small
circuit (well stole actually from the VT100 schematics) that generated a
composite video signal from the TTL signals generated by the VT52?
Oh ? this is a cool idea! Will keep in the bag of tricks if necessary for
future work on the VT52.
@Fritz: You don't need to get a dump of the
PROMs in your terminal. I
think
the ones I have is in pretty good shape.
You beat me to it! I think I will still upgrade my PROM sockets over this
holiday break, and will just go ahead and dump the PROMs while I?m at it
since I?ll have them out anyway. Mine are labeled the same as the ones you
listed.
cheers,
?FritzM.
6:52 p.m.
On Dec 26, 2017, at 2:22 PM, Mattis Lind <mattislind at gmail.com> wrote:
Before putting everything together I also dumped the chargen ROM board?
Ah, yes ? I did this with my own VT52 last xmas break! I breadboarded a little scanner
for that task because my chargen ROM was not socketed, and I didn?t want to risk damaging
it by unsoldering it from the board:
http://fritzm.github.io/vt52.html <http://fritzm.github.io/vt52.html>
https://github.com/fritzm/vt52 <https://github.com/fritzm/vt52>
It?s a pretty cool and funky little font, and since I spent a lot of time in front of
VT52s back in the day it makes me nostalgic. I hope someday somebody with decent
font-smithing skills will use the data to make a usable console font; my experiments with
font creation tools were not a great success and I came to the conclusion that there is a
lot I don?t know about fonts which is necessary in order to make them render and scale
well and be generally usable on modern operating systems...
cheers,
?FritzM.
2405
days inactive
2407
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4 comments
3 participants
participants (3)
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fritzm＠fritzm.org -
jnc＠mercury.lcs.mit.edu -
mattislind＠gmail.com