The recent discussion on BSC protocol prompted me to dig out my Microvax 3100
with DSH32 synchronous serial interface. It had been idle in storage for
several years and it wouldn't power up, only giving a brief flash on the
diagnostic LEDs and a quick twitch of the fans. There was a slight smell, like
the stale air that comes out of a deflating tyre.
I took out the H7821 power supply and found that five identical brown 1800uF 25V
electrolytic capacitors on the output side had leaked.
The SCSI disk enclosure where the machine's system disk lives required several
power cycles to get it to run at all and it died as soon as the disk tried to
spin up. It turned out to also contain a H7821 power supply which had a
similar issue with the same five brown capacitors, although not as extensive
as in the main unit.
I found a second disk enclosure which had seen little use and grabbed the power
supply out of that to put in the MicroVAX. It worked well enough to test with
but there was a ring of goo around the bottom of one of the brown capacitors
which was worst affected in the other units. Time to order a batch of
replacement capacitors and figure out what else has been damaged. While it is
not the worst I have seen, access to these power supplies for repairs is quite
difficult and it is really difficult to debug them safely while they are
running with the cover off :-(
If anyone has anything with H7821 power supplies in them, I suggest checking
on these capacitors. If anything with these power supplies is in storage, I
suggest ensuring it is stored the normal way up as this should limit the
ability of the goo to escape and spread around the power supply.
And there I was thought I was being safe enough by removing the nicad battery
packs some years ago...
> From: Mattis Lind
> Thanks Noel for sorting this out.
Eh, de nada. But thank you.
>> I wonder if the ucode in the two versions is identical? The uROM chip
>> numbers should give it, (if they are the same on both versions, albeit
>> in different locations on the board), but I have yet to check. Does
>> anyone happen to know?
OK, so the situation here is pretty complicated. To start with / make things
worse, that CPU uses lots of PROMs. Lots and lots and lots and lots of PROMs.
For the data paths board (M7260), both major versions appear to contain the
same PROMs (going by the DEC part numbers), but the chip location (Exx)
numbers are all different.
For the control board (M7261), the C, E ('early' version) and F ('late'
version) etch revisions each contain mostly the same PROMs, but apparently
with slight differences between the sets of PROMs in each (as reflected in
different DEC part numbers). For details see:
to which I have just added all the gory details.
As to getting the contents of all of them dumped in machine-readable form -
>> on the earlier version (prints for that version are in the GT40 prints
It turns out that I have hard-copy prints for the "C" etch revision of the
M7261, which do not yet appear to be online; the GT40 prints have the "E"
I will scan the pages for that revision of the board, and put them up 'soon'.
(I'm not doing the whole print set, it's about 1" thick, and most of them are
for other things anyway, like MM11-L memory, etc.)
CHM doesn't seem to have much early DSP stuff in the collection
Does anyone have any of the TMS32010/20/30 or C1x/2x/3x hw/sw kicking around?
Other than the docs I've scanned there doesn't seem to be much on the web either.
> From: Toby Thain
> To get closer I'd need better images of the panels.
Hi, I borrowed a DEC inlay from someone (a KA10 CPU bay) and scanned a chunk
of it (as much as I could fit into my A4 scanner :-) at 200 dpi:
I have a TC08 inlay, but it's currently being used in my QSIC display (until
we can get the RKV11-F/RPV11-D inlay done :-), and I didn't want to yank it
out. As far as I can tell, it's the same font on the two of them.
> the closest I know of off the top of my head is Akzidenz Grotesk.
The Akzidenz Grotesk Medium is indeed very, very close (other than the zero).
Do you happen to know if that font available for use in non-commercial
The following four monitors are available free for pickup in the UK
All appear clean but are untested. All are believed to have been
functional when stored but that was ~2002/2003-ish.
Microvitec Cub. Seems to be in its original box.
Vision Master Pro 17.
Obviously with the current restrictions on movement these cannot be
picked up, but they need to be gone soon after the restrictions are over.
Expressions of interest offlist please.
antonio at acarlini.com
I'm the proud owner of a PDP11/05 system with a couple of 8" floppy
drives. I believe they are likely to be RX01s.
Does anybody on the list have some boot media that they could provide. I
understand that the controller can't format the disks so I'm in a
frustrating state where I don't know where to start.
Wonderful: A few weeks ago I forgot to turn off my VT52 and left it
running for a day or two. Now the screen is filled with snow and it
looks like the text is all over the place horozontally.
Any tips or thoughts on where to start looking to fix? The keyboard
seems to be working as does the RS232 input (the snow on the screen
changes when the pdp11 talks to it)
>From time to time there are posts here about the Facit N4000 paper
tape punch/reader unit. The one that looks like a Facit 4070 with a
tape reader on the front (in fact the punch mechanism is much the same
as that in the 4070).
I have reverse-engineered mine and traced out the schematics. Of
course it's one of my hand-drawn ones but I think it's mostly legible.
If anyone wants it I am happy to send out a copy (but as ever I'd
rather send it out once and have somebody else pass it on)
Hi - COVID project.... I have been attempting to read some old Honeywell
DDP-516 papertapes using the OP-80A or Teletype reader but it's inefficient
and I don't want to damage the tapes. Does anyone have a reliable
papertape reader for sale, or recommend one currently out there on Ebay,
for the purpose of archiving papertapes of any kind safely and reliably. I
have a reasonable budget. I have a lot of tapes that need to be archived,
so I'd want one that I can interface with to capture into TAP files or what
I would call a raw dump listing of the data in 8-bit Hex. MITS, SWTPc,
Z80 stuf, PDP 8, PDP 11, Honeywell, etc.
End goal is to load tapes into simH, PDPGUI, Altair/S-100, textfiles to
display tapes. I want to be able to view the tape as it would be in Intel
or Motorola format, etc. What does everyone else do?
Thanks for any advice.