23 Dec
2017
23 Dec
'17
12:08 a.m.
I have started to work on a getting VT50 terminal back to life. When
digging into it I recognze quite immediately that someone had done a brain
transplant on it. It has VT52 boards in it!
Was this a usual procedure?
The VT50 to VT52 shift looks like a failure of DEC at the time. So close in
time. But different board sets inside. They could have designed a board
with RAM upgrade possibility and just a new microprogram? Looks strange to
me. When the VT52 got on the market I guess it was hard to sell any VT50s
or was there a substantial price difference?
Anyhow, the VT52 boards are dead. They generate the proper sync signals but
there are no keyclick generated when pressing keys on the keyboard. Which
is quite normal since the sync is generated by a chain of counters while
the keyboard is controlled by the microprogram. The terminal uses 4 pieces
of 256 by 4 bipolar PROMs for a total of 512 bytes of microprogram.
Has anyone dumped the contents of these so I could verify them?
23 Dec
23 Dec
1:08 a.m.
Hi Mattis,
On Dec 23, 2017, at 12:08 AM, Mattis Lind via cctalk
<cctalk at classiccmp.org> wrote:
Anyhow, the VT52 boards are dead. ? The terminal uses 4 pieces
of 256 by 4 bipolar PROMs for a total of 512 bytes of microprogram.
Has anyone dumped the contents of these so I could verify them?
I have a restored VT52. Taking a peek, I see these PROMs are socketed, so I can pull mine
this weekend and give them a read for you no problem.
I actually had a lot of trouble with a flaky oscillator when I was working through my
VT52, but it sounds like your?s is going fine if you are observing the whole timing chain
including video sync?
cheers,
?FritzM.
4:32 a.m.
2017-12-23 10:08 GMT+01:00 Fritz Mueller <fritzm at fritzm.org>:
Hi Mattis,
Yes, the oscillator seems to work. But it is a pain to work with the VT52
since the print set has very little information. Where is the component
list? I cannot verify which PROM should go into what location. And the damn
boards doesn't have any component designator anywhere, nor is there
anything on the component placement info in the print set on the data path
board.
The PROMs in my machine are: 23-124A9, 23-125A9, 23-126A9 and 23-127A9. Is
this the same as your VT52? Apparently there is an earlier PROM set as
well.
It would be very nice if you could tell me the location of the PROM chips
as well.
/Mattis
On Dec 23, 2017, at 12:08 AM, Mattis Lind via
cctalk <
cctalk at classiccmp.org> wrote:
Anyhow, the VT52 boards are dead. ? The terminal uses 4 pieces
of 256 by 4 bipolar PROMs for a total of 512 bytes of microprogram.
Has anyone dumped the contents of these so I could verify them?
I have a restored VT52. Taking a peek, I see these PROMs are socketed, so
I can pull mine this weekend and give them a read for you no problem.
I actually had a lot of trouble with a flaky oscillator when I was working
through my VT52, but it sounds like your?s is going fine if you are
observing the whole timing chain including video sync?
cheers,
?FritzM.
5:34 a.m.
2017-12-23 13:32 GMT+01:00 Mattis Lind <mattislind at gmail.com>:
2017-12-23 10:08 GMT+01:00 Fritz Mueller <fritzm at fritzm.org>:
I did some more research into the terminal after I put the christmas ham
steak into the oven and christmas rice pudding on the stove.
There were nothing going on at the microprogram outputs. All high. It
turned out that the CE input for the PROMS was high for ALL banks!
Impossible! A 7400 at E34 was not doing well. After replacing that there
are some life in the microprogram and I have some random klicks from the
key klick relay. But still not working as it should. So more interesting
fault finding ahead! 20+ years sitting in a cold attic probably is not good
at all.
Hi Mattis,
Yes, the oscillator seems to work. But it is a pain to work with the VT52
since the print set has very little information. Where is the component
list? I cannot verify which PROM should go into what location. And the damn
boards doesn't have any component designator anywhere, nor is there
anything on the component placement info in the print set on the data path
board.
The PROMs in my machine are: 23-124A9, 23-125A9, 23-126A9 and 23-127A9. Is
this the same as your VT52? Apparently there is an earlier PROM set as
well.
It would be very nice if you could tell me the location of the PROM chips
as well.
/Mattis
On Dec 23, 2017, at 12:08 AM, Mattis Lind via
cctalk <
cctalk at classiccmp.org> wrote:
Anyhow, the VT52 boards are dead. ? The terminal uses 4 pieces
of 256 by 4 bipolar PROMs for a total of 512 bytes of microprogram.
Has anyone dumped the contents of these so I could verify them?
I have a restored VT52. Taking a peek, I see these PROMs are socketed,
so I can pull mine this weekend and give them a read for you no problem.
I actually had a lot of trouble with a flaky oscillator when I was
working through my VT52, but it sounds like your?s is going fine if you are
observing the whole timing chain including video sync?
cheers,
?FritzM.
9:51 a.m.
On 12/23/2017 5:34 AM, Mattis Lind via cctalk wrote:
2017-12-23 13:32 GMT+01:00 Mattis Lind <mattislind
at gmail.com>:
I've been tinkering with a VT52 at the museum.? I found that the sockets
for the PROMs are of poor quality and were not making good connections.?
This may not be a problem in your case, but it's something to take a
look at if you haven't already.
- Josh
Yes, the oscillator seems to work. But it is a
pain to work with the VT52
since the print set has very little information. Where is the component
list? I cannot verify which PROM should go into what location. And the damn
boards doesn't have any component designator anywhere, nor is there
anything on the component placement info in the print set on the data path
board.
The PROMs in my machine are: 23-124A9, 23-125A9, 23-126A9 and 23-127A9. Is
this the same as your VT52? Apparently there is an earlier PROM set as
well.
It would be very nice if you could tell me the location of the PROM chips
as well.
/Mattis
I did some more research into the terminal after I put the christmas ham
steak into the oven and christmas rice pudding on the stove.
There were nothing going on at the microprogram outputs. All high. It
turned out that the CE input for the PROMS was high for ALL banks!
Impossible! A 7400 at E34 was not doing well. After replacing that there
are some life in the microprogram and I have some random klicks from the
key klick relay. But still not working as it should. So more interesting
fault finding ahead! 20+ years sitting in a cold attic probably is not good
at all.
>
>> cheers,
>> ?FritzM.
>>
>>
10:34 a.m.
2017-12-23 18:51 GMT+01:00 Josh Dersch via cctalk <cctalk at classiccmp.org>:
On 12/23/2017 5:34 AM, Mattis Lind via cctalk wrote:
2017-12-23 13:32 GMT+01:00 Mattis Lind <mattislind at gmail.com>:
God point. I did re-seat all the PROMs, but there were no difference. When
pushing a IC clip-on to the chip it appears that ICs slips out of the
socket which probably means that the force in the contacts to hold the IC
in place is not the best. Maybe I should just replace them to be sure.
I found another ITT made 7400 that was bad, E8 on the UART & timing board.
One output was always at 2V indicating that it was open circuit (pulled up
by the input of the connected TTL).
/Mattis
Yes, the oscillator seems to work. But it is a pain to work with the VT52
I've been tinkering with a VT52 at the museum. I found that the sockets
for the PROMs are of poor quality and were not making good connections.
This may not be a problem in your case, but it's something to take a look
at if you haven't already.
since the print set has very little information.
Where is the component
list? I cannot verify which PROM should go into what location. And the
damn
boards doesn't have any component designator anywhere, nor is there
anything on the component placement info in the print set on the data
path
board.
The PROMs in my machine are: 23-124A9, 23-125A9, 23-126A9 and 23-127A9.
Is
this the same as your VT52? Apparently there is an earlier PROM set as
well.
It would be very nice if you could tell me the location of the PROM chips
as well.
/Mattis
I did some more research into the terminal after I put the christmas ham
steak
into the oven and christmas rice pudding on the stove.
There were nothing going on at the microprogram outputs. All high. It
turned out that the CE input for the PROMS was high for ALL banks!
Impossible! A 7400 at E34 was not doing well. After replacing that there
are some life in the microprogram and I have some random klicks from the
key klick relay. But still not working as it should. So more interesting
fault finding ahead! 20+ years sitting in a cold attic probably is not
good
at all.
- Josh
> cheers,
>> ?FritzM.
>>
>>
>>
11:39 a.m.
The most documentation I?ve seen re. the PROMs is pages A-1 and A-2 of the VT52
maintenance manual here:
http://www.pdp8.net/pdp8cgi/query_docs/tifftopdf.pl/pdp8docs/ek-vt52-mm-002…
I think you?ve probably seen that already. I?ll post more info from my VT52 later when I
make it downstairs to my shop later.
I have noticed the flaky PROM sockets also; maybe I?ll just go ahead and replace them
since I?ll have mine out on the bench anyway.
Mattis? place probably smells like ham, pudding, and 70?s-era solder flux right now ?
sounds like a good holiday :-)
?FritzM.
1:02 p.m.
l?r 2017-12-23 klockan 11:39 -0800 skrev Fritz Mueller via cctalk:
The most documentation I?ve seen re. the PROMs is
pages A-1 and A-2 of the VT52 maintenance manual here:
http://www.pdp8.net/pdp8cgi/query_docs/tifftopdf.pl/pdp8docs/ek-vt52-mm-002…
I think you?ve probably seen that already. I?ll post more info from my VT52 later when I
make it downstairs to my shop later.
I have noticed the flaky PROM sockets also; maybe I?ll just go ahead and replace them
since I?ll have mine out on the bench anyway.
Mattis? place probably smells like ham, pudding, and 70?s-era solder flux right now ?
sounds like a good holiday :-)
?FritzM.
Hmm, i think maybe his place has a smell like this:
stearinljus (candles)
some gl?gg (mulled wine)
julskinka (ham)
or as in our case:
lutfisk (dried ling later on soaked in lut and boiled) och potatis
(potatoes) och vits?s (a white sauce.)
1:14 p.m.
Don't forget the prinskorv and lax (it's expensiv... err, it's good*).
*For the non-Swedes (or those without a Swedish partner), see
https://www.youtube.com/watch?v=vmeSmOsi-fY
On Sat, Dec 23, 2017 at 9:03 PM Stefan Skoglund via cctalk <
cctalk at classiccmp.org> wrote:
l?r 2017-12-23 klockan 11:39 -0800 skrev Fritz Mueller
via cctalk:
http://www.pdp8.net/pdp8cgi/query_docs/tifftopdf.pl/pdp8docs/ek-vt52-mm-002…
The most documentation I?ve seen re. the PROMs is
pages A-1 and A-2 of
the VT52 maintenance manual here:
I think you?ve probably seen that already. I?ll post more info from my
VT52 later
when I make it downstairs to my shop later.
I have noticed the flaky PROM sockets also; maybe I?ll just go ahead and
replace
them since I?ll have mine out on the bench anyway.
Mattis? place probably smells like ham, pudding, and 70?s-era solder
flux right
now ? sounds like a good holiday :-)
?FritzM.
Hmm, i think maybe his place has a smell like this:
stearinljus (candles)
some gl?gg (mulled wine)
julskinka (ham)
or as in our case:
lutfisk (dried ling later on soaked in lut and boiled) och potatis
(potatoes) och vits?s (a white sauce.)
6:33 p.m.
Well, cod soaked in lye for a couple of days might well require something that starts or
ends with 'lax' all right...
m
----- Original Message -----
From: "Yvan Janssens via cctalk" <cctalk at classiccmp.org>
To: "Stefan Skoglund" <stefan.skoglund at agj.net>; "General
Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
Sent: Saturday, December 23, 2017 4:14 PM
Subject: Re: Restoring a VT50 (VT52 actually) .
Don't forget the prinskorv and lax (it's expensiv... err, it's good*).
*For the non-Swedes (or those without a Swedish partner), see
https://www.youtube.com/watch?v=vmeSmOsi-fY
On Sat, Dec 23, 2017 at 9:03 PM Stefan Skoglund via cctalk <
cctalk at classiccmp.org> wrote:
l?r 2017-12-23 klockan 11:39 -0800 skrev Fritz Mueller
via cctalk:
http://www.pdp8.net/pdp8cgi/query_docs/tifftopdf.pl/pdp8docs/ek-vt52-mm-002…
The most documentation I?ve seen re. the PROMs is
pages A-1 and A-2 of
the VT52 maintenance manual here:
I think you?ve probably seen that already. I?ll post more info from my
VT52 later
when I make it downstairs to my shop later.
I have noticed the flaky PROM sockets also; maybe I?ll just go ahead and
replace
them since I?ll have mine out on the bench anyway.
Mattis? place probably smells like ham, pudding, and 70?s-era solder
flux right
now ? sounds like a good holiday :-)
?FritzM.
Hmm, i think maybe his place has a smell like this:
stearinljus (candles)
some gl?gg (mulled wine)
julskinka (ham)
or as in our case:
lutfisk (dried ling later on soaked in lut and boiled) och potatis
(potatoes) och vits?s (a white sauce.)
1:23 p.m.
On 12/23/2017 01:02 PM, Stefan Skoglund via cctalk wrote:
stearinljus (candles)
some gl?gg (mulled wine)
julskinka (ham)
or as in our case:
lutfisk (dried ling later on soaked in lut and boiled) och potatis
(potatoes) och vits?s (a white sauce.)
Add the odor of some failed selenium rectifiers and you'll really have
something to talk about!
--Chuck
3:26 p.m.
Chuck Guzis via cctalk wrote:
On 12/23/2017 01:02 PM, Stefan Skoglund via cctalk
wrote:
:-)
in german that devices are called "Gleichrichter" (Rectifier)
an abbrevation is "gleich riecht er" what means something like
next time it smells ...
Regards,
Holm
--
Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe,
Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583
info at tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741
stearinljus (candles)
some gl?gg (mulled wine)
julskinka (ham)
or as in our case:
lutfisk (dried ling later on soaked in lut and boiled) och potatis
(potatoes) och vits?s (a white sauce.)
Add the odor of some failed selenium rectifiers and you'll really have
something to talk about!
--Chuck 
9:13 p.m.
No Aebleskivers and Julekage? I baked the Danish variety of Julekage
yesterday.
On Sat, Dec 23, 2017 at 3:02 PM, Stefan Skoglund via cctalk <
cctalk at classiccmp.org> wrote:
l?r 2017-12-23 klockan 11:39 -0800 skrev Fritz Mueller
via cctalk:
The most documentation I?ve seen re. the PROMs is
pages A-1 and A-2 of
the VT52 maintenance manual here:
pdp8docs/ek-vt52-mm-002.pdf
I think you?ve probably seen that already. I?ll post more info from my
VT52 later
when I make it downstairs to my shop later.
I have noticed the flaky PROM sockets also; maybe I?ll just go ahead and
replace
them since I?ll have mine out on the bench anyway.
Mattis? place probably smells like ham, pudding, and 70?s-era solder
flux right
now ? sounds like a good holiday :-)
?FritzM.
Hmm, i think maybe his place has a smell like this:
stearinljus (candles)
some gl?gg (mulled wine)
julskinka (ham)
or as in our case:
lutfisk (dried ling later on soaked in lut and boiled) och potatis
(potatoes) och vits?s (a white sauce.)
2337
days inactive
2338
days old
12 comments
9 participants
participants (9)
-
cclist＠sydex.com -
derschjo＠gmail.com -
fritzm＠fritzm.org -
holm＠freibergnet.de -
infected＠analprolap.se -
mattislind＠gmail.com -
mhs.stein＠gmail.com -
stefan.skoglund＠agj.net -
useddec＠gmail.com