Anyone ever attempt repairs on CTI boards for DEC Professionals?

Ethan Dicks ethan.dicks at
Tue Apr 30 11:32:07 CDT 2019

Hi, All,

In preparing for my VCF-East exhibit, I went through my stack of DEC
Pro gear.  The good news is I had enough working hardware to get a
Pro350 running Venix fully operational.  The bad news is that I don't
have enough working hardware to have even a second functional Pro.

One of my RX50 controllers has a mechanically bunged up CTI ZIF
socket.  It doesn't look repairable so I'm probably going to have to
replace it with a transplant from another board.

One of my standard (mono) video cards displays bit garbage on
power-up.  I haven't found schematics for it yet (bitsavers has
schematics for the Pro380 CPU, the RX50 controller, the RX50, the
RD50).  I could probably pull the RAM and test it outside the board,
but beyond that, I'm stabbing at things.

I did a lot of googling around and I haven't seen a lot of repair
details on these.  Not really surprised about that, but I figure it
was worth asking if anyone has attempted component-level repair on DEC
Professionals.  I'm sure there's lots of experience with board
swapping - that will definitely solve my problems.

Oh... and I happen to be one video controller short anyway.  I suppose
a partial machine made its way to me at some point.  I know my Pro380
used to be a console for our 8530.  I was able to rescue the console
at least.  I probably got the Pro350s sometime in the mid-1990s when
people were dumping them.  I'm still a bit puzzled why I have *5* 256K
memory cards.  There's only 6 slots and once you put in the RX50
controller, the RD controller, the video card, and possibly the color
bitplane extension card, you've got 2 slots left.

One fun bit - I was able to break into the Venix box using the 'guest'
account (I guessed there was one) and run John the Ripper on an i7
Linux laptop to crack all the hashes.  10/12 took literally seconds.
One password was '82', another was 'Bob'.  The root password took a
few hours because it was two dictionary words.  In the end, though,
they all fell.  The default root password for Venix is in the manuals
('gnomes').  They at least changed it on this box, but 1984 crypto is
no match for 21st Century cracking.

I don't see DEC Pro systems talked about much - they were kinda slow
and definitely limited in their expansion.  For a time, they were a
cute packaged PDP-11 system but that CTI bus connector is a royal
PITA.  I am not shocked there weren't that many peripherals for it,
but for a "desktop computer", how many different kinds of interfaces
does the average office user need?

If anyone happens to be coming to VCF East this weekend and has dead
Pro gear, I could use a card to pull a CTI connector from.  At least I
should be able to get the one RX50 controller going.


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