5 Apr
1999
5 Apr
'99
4:40 a.m.
<Alas it isn't... We're both right. The 8/e panel uses diode gates (in the
<maintenance manual, printset and the physical machine on my desk). The
<8/f uses TTL gates.
The last 8e pannel I worked with was also ttl. there may have been two
versions (very likely).
The offending part was a 74L54 with a bad input. It's now mostly up and
ready for more testing.
Allison
5 Apr
5 Apr
12:23 p.m.
At 05:40 AM 4/5/99 -0400, Allison J Parent wrote:
The last 8e pannel I worked with was also ttl. there
may have been two
versions (very likely).
Actually you can date '8s by their front panels ;-) The original PDP-8/E
panel used diodes and a separate lamp supply. At some point (between 1970
and 1972) it was re-designed to use TTL and at the same time the need for
the separate lamp supply was removed, later the lamp sockets were rewired
to accept LEDs (lamps burn out a lot), and then later still (about 1972+)
the LEDs were wired directly on to the panel. I believe, but have not had a
true digit confirm, that the 8/F was named such because the panel had
evolved to the point where it no longer looked like an "E". Clearly the
front panel graphics were redesigned a bit but not much else. The 8/M is
exactly the 8/F with a different decal plate and switch colors (the light
and dark hues are exactly reversed) [If you look at Megan's picture of the
'haul' you can see this in the 8/e and 8/f]
Anyway, if you've got a TTL front panel they are all pretty much the same.
The 8/e/f/m printset only describes this panel.
--Chuck
1:52 p.m.
the separate lamp supply was removed, later the lamp
sockets were rewired
to accept LEDs (lamps burn out a lot), and then later still (about 1972+)
the LEDs were wired directly on to the panel. I believe, but have not had a
true digit confirm, that the 8/F was named such because the panel had
evolved to the point where it no longer looked like an "E". Clearly the
As an exDIGIT and having a 8F (stamped feb 1973) this is indeed true.
The 8/e/f/m printset only describes this panel.
The CS is 54-09968-xx is the same for all late 8e/f/m machines.
Allison
5:48 p.m.
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6:37 p.m.
At 11:48 PM 4/5/99 +0100, you wrote:
My machine came with the 8/e (only) printset which
describes only the
diode-logic panel, and also the 3-volume maintenance manual (for the
e,f,m) that describes both panels (but implies the 8/e has the diode logic
panel and the 8/f and 8/m have the TTL panel).
I've got one of each, a non-working 8/E panel using the diode logic and an
8/E panel that uses TTL. The latter is really cool since it still uses
lamps but they are 5v versions rather than the 8v lamps of the original. I
do however minimize the hours on that panel since I worry about the lamps
burning out. (I've got three spares left ...)
On an interesting note is the availability of "white" LEDs (actually R, G,
and B leds all wired together in the same case). This leaves open the
possibility of replacing lamps with white LEDs continuing to keep the 8/e
in service as it was intended. (I also scavenge wheat lamps when I see 'em!
--Chuck
7:32 p.m.
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