As posted previously I am trying to repair my VT100 and I am having trouble
with the Monitor Board. The one I have does not match the available printset
(PDF p54 of this
https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Schematic_Feb82.p
df). My VT100 appears to match the older
https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Mar80.pdf
printset, but it doesn't cover the monitor board.
My monitor board looks as follows
https://rjarratt.wordpress.com/wp-content/uploads/2023/12/img_20231221_11223
3.jpg and the two big transistors on the left appear to be incorrect parts
possibly from a previous repair attempt before I got the VT100.
Does anyone have a previous revision of the VT100 with a Monitor Board that
matches mine? If so, would you be able to photograph it please, or tell me
what parts are installed for the two TO-3 transistors on the left? Better
still would be if anyone has the printset for this version of the monitor
board.
Thanks
Rob
One of the greatest joys of classic computing was running what you wanted
on your own computer. What has happened in the intervening years? Have
‘software walls’ created a computing environment that benefits software
gate-keepers(owners of computing technology) by monopolizing creativity,
freedom to program and establishing a defacto ‘true ownership’. Will the
future be this or will it be more like the earliest years of
microcomputing?
Murray 🙂
I’ve recently come across 1/2 of an upgrade kit for the VT180 ( which upgrades it to a CP/M based machine — see : https://dunfield.classiccmp.org/dec/vt18x.pdf ). A friend around the same time rescued a floppy chassis which was also part of the upgrade.
The problem is that we’re missing the PCB parts of the upgrade. This includes the VT180 paddle board, the VT18X Control board and maybe the VT100 expansion backplane. ( I haven’t opened up my VT100 to see what it has inside - I’ve only used it as a terminal ). ROM images are available and the partial kit I believe has all the standoffs, cables, badge, etc.
Anybody know if anybody has made any reproduction PCBs for this upgrade? Or anybody know where I might find any of these parts? It would be fun to perform this upgrade and show it off at our next VCF-SE.
Thanks in advance for any pointers.
Earl
Sent from my iPhone’s
I asked this before a few years ago but didn't come to a firm conclusion. The two parts are shown in this picture: https://rjarratt.wordpress.com/wp-content/uploads/2023/12/img_20231221_1123…
They are from a VT100 Monitor board. There is no schematic for my version of the board, but a related schematic is on p58 of this schematic: https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Schematic_Feb82.…. They are labelled Q414 and CR406, but the Feb 82 revision uses a different board and those two parts are in TO-220 packages rather than TO-3 as here..
I have removed both of them and tested them with a DMM. Neither of them measure as two diodes, they do not measure open circuit in any direction, so either they are both faulty or they are not transistors (unlikely). I have found a spec for a 2SB411 at https://alltransistors.com/transistor.php?transistor=10279. This seems to be a germanium transistor. When I last asked about this I had a conversation with Tony Duell, who was very sceptical that these could be germanium transistors, so naturally I am very doubtful that they are 2SB411 transistors. However, in the schematic Q414 is shown as NPN, the 2SB411 is PNP and this seems to match the way the part is connected on my board (Collector to HORIZ GND). I am working on a reverse engineered schematic.
Can anyone tell me what these components are so I can find a datasheet for them? Better still a suggested replacement would be really helpful, especially if they are 2SB411s because they seem to be hard to find.
Thanks
Rob
...soon!
Hotel room booking for the Vintage Computer Festival Midwest will open via
the link on our site at 22:00 Central Time (that's about 20 minutes from
now). Here is the link:
https://vcfmw.org/hotel
-jt
Can someone explain how the Intel 8008 (yes, the 8008, NOT the 8080!)
handled saving and restoring the flags during an interrupt?
The 8008 has four flag bits - CZS&P - but there doesn't seem to be any
explicit equivalent to the PSW register nor any "PUSH PSW" or "POP PSW" type
instructions. Other than testing the flag bits with the JUMP/CALL/RET
instructions there doesn't seem to be any way to access them.
Interrupts work pretty much like the 8080 - during the interrupt response
the peripheral forces an instruction onto the bus, typically an RST opcode
but in theory it could be anything. RST and CALL however only appear to
save the PC on the internal stack, and RET only restores the PC. So how do
you save and restore the flag bits?
It seems like interrupts would be pretty much useless without this, so I
must be missing something.
Thanks,
Hi there,I recently completed recreations of the Sol Intelligent Terminal and JOLT PCBs and have had a bunch produced if anyone is interested.But the real reason I am writing is I want to tackle a much more difficult project which is the RGS-008, which came out around the time of the Altair and was condemned obsolescence almost immediately following release.I am trying to track down any surviving copies of schematics or documentation. I have already reached out to CHM and a couple other folks but so far actual documentation remains elusive. CHM does have an RGS-008 based on the original wire wrap design, but no schematics.Probably these things are hard to find for a reason, but I thought I might reach out here to see if anyone has any other leads I could possibly follow. I suspect the basic design followed the reference design supplied by Intel, with some modifications. Many thanks and Happy New Year!BradSent from my Galaxy
Hey all -
I came across a big box of 12 of these disks which my dad acquired through
work back in the 70s, and squirreled them away in the attic after they had
copied the data. 4 of them have a broken metal access door. I opened one of
the broken ones (in a clean of an environment as possible) to see what was
going on inside. It looks like the door is held on by plastic divets that
have broken off. They might be able to be repaired with small screws. I
have no idea if these are functional or not. I am offering them up for free
for anyone that can use them. I'm willing to ship or you pick up in San
Diego.
Here is a link to photos of them:
https://drive.google.com/drive/folders/1wnzqjAtiq44MGU-wDJR-AQdzu-Mkyii8?us…
-Kurt
