There have been a few versions of the utility imd2raw.c floating around
that will take Dave Dunfield's ImageDisk-created images (i.e. an .IMD file)
and make a linear binary image devoid of any metadata. This is similar to
the function of Dave's IMDU.COM program's /b switch.
I've corrected a problem with the assumption that all imd2raw.c descendants
to date have made: sectors that have a skew (i.e. not 1-1 interleaved)
weren't linearized correctly. The skewed sectors need to be written out in
"sorted" order, which is not necessarily captured/physical order. This is
easily verified by comparing output from "IMDU /b" to earlier imd2raw
outputs on any .IMD that has a sector skew that isn't 1, 2, 3 [...].
It's up on github here:
https://github.com/RetroFloppy/imd2raw
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
Hello,
I'm an employee with the National radio astronomy observatory here in Socorro New Mexico.
As part of our NGVLA upgrades, we are seeking to get rid of old data tapes from the tape reel days of Computing. These contain things such as the boot loaders, OS, specific collection programs and antenna movement programs.
I personally would hate to see these just wind up in the literal dumpster and would like to see them sent out to a museum or an archiving body that can preserve them and keep them safe as a dynamic part of history.
If anyone is interested or knows someone who would be interested in the VLAs data tape library please let me know.
V/R
Danielle Werts
Front end engineer
VLA Socorro New Mexico
VCF Montréal 2026 was a great success! Please fill out *one* of these
anonymous surveys about the event:
English: https://bit.ly/vcfm2026post-en
VCF Montréal 2026 a été un franc succès ! Veuillez remplir *un* de ces
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Jeff Brace
VCF National Board Member Chairman & Vice President
Dear administrators,
Once again Gmail users appear to have been disabled. Could you please help
and re-enable me and others who have been affected. It is only 3 or 4
months ago when this happened last. It would be nice if this could be fixed
permanently.
Thanks and best regards
Tom Hunter
I bought a reel of paper tape at an office supply shop today.
It was in their 'bargains' room and is marked
NCR
SYSTEMEDIA
01-6388181
Telex 888634
PTI
Made in England
It cost me £0.50. I think they had two more reels. it's age is indicated by
having a London phone number that was made obsolete 30 years ago.
However, what surprises me is that it's 17.5 mm (0.69", 11/16") wide. This
seems too narrow for 7-hole tape and too wide for the tape used for
telegrams. Is it for 5-hole tape ?
Hi all,
I have a controller card (i'll elaborate later in the message) for an
ICOM 3712 8" floppy drive unit. However, i do not have an FD3712 system
to interface to it!
With Shugart style floppy emulation essentially a solved problem, i'm
wondering if similar has been done for the FD3712. As the computer side
of the floppy interface is just a parallel interface, and all the disk
geometry wizardry happens on the FD3712, i'd assume a lot of the
difficulty of Shugart floppy emulation is essentially a moot point. So
the question is, is there a project already existent to replace the
FD3712 unit with an emulated (raspberry pi based?) alternative?
I'm asking the question as i have an RCA Microboard bus CDP18S646
combined Centronics Printer interface and FD3712 floppy interface. It
also came with an MBZ80 z80 based CPU card, and i'm putting 2 and 2
together and gathering it was likely the two were used together. If i've
every got a a hope in hell of booting anything, solving the media
problem is quite important.
Cheers,
Josh Rice
