Re: Looking for an T5611-25 CRT (or -7 or -2)


We had a PDP-12 in our lab years ago. We got it when another department was
discarding it and we adopted it. Ours had a different color scheme from the
LINC-8 systems, but it was the same machine. Ours had a A-D converter in
the rack above the scope - the same modified Tek scope that is in yours. We
played “Spacewar” on it (we did use it for some lab data acquistion work).
It had a pair of DECtape drives.

The engineer I shared the lab with left a couple of years before I did.
When I left, I left that PDP-12 behind along with Tek 585 and 547 (the one
scope I wish I had taken with me) scopes. I did take the 556 but it sat on
my bench at home unused. I sold it off at a hamfest (should have kept that
one, too). The PDP-12, a PDP-8 system (DF-32 disk, two DECtape drives, 8K
memory, high-speed paper tape reader and punch, plus the ubiquitous ASR-33
Teletype), and the Tek scopes were all offered to me. Since I didn’t take
it, it all went into storage in an area of the building that was slated for
then future development. When I visited a few years later, what had been
“shell” space had been fully developed. All that stuff got scrapped.

As I recall, that modified Tek scope in the PDP-12 had a separate
edge-lighted graticule. The plug-ins were the same in each plug-in bay and
were basically amplifiers to run the scope in XY mode.

Seeing the photos of the LINC-8 brought back memories of using those front
panel switches to key in the RIM loader so we could load the BIN loader
from the ASR-33 (slow and noisy). On the PDP-8, we still had to enter the
BIN loader, but could then load the RIM loader from the high speed reader.
If we were not doing a cold start, we could also start up from the DF32
disk or DECtape. I did use the Tek scopes for troubleshooting - usually the
Teletype and trying to look at the various timing signals in it or the
current loop interface when it wasn’t working right.

On Sun, Jul 11, 2021 at 23:02 Bob Rosenbloom <> wrote:

I know this is a long shot, but I'm looking for an T5611-25 CRT for use in
restoring an DEC LINC-8 minicomputer.
It used a modified Tektronix 561B oscilloscope, with DEC plug-ins, and the
P25 phosphor CRT with no graticule.
The one in the LINZ has a badly burned face. A P7 or even P2 phosphor
would also work though would look
different than the original. So basically any slow phosphor and no

Some cell phone photos of the LINC and scope are on my web site here:

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