13 May
2014
13 May
'14
2:13 a.m.
analog? from my point of view it's just the equivalnt of a huge power
mosfet like a irf830 driven by a small signal from the 8/l
first of: does the 8/l change a level on the wire? check that with a
multimeter. if not: look at your 8/l, if yes, look at the dec board.
it is possible that the line itself does not carry a voltage but is tied
to gnd in the computer. if there is no voltage on the line, switch the
multimeter to resistance and check the change of values. reverse the
leads if nothing comes up.
eliminating possibillities is the first part in faultfinding.
simon
On 13-05-14 08:03, Josh Dersch wrote:
Hi all --
Finally have the time (and space) to work on my PDP-8/L and its
associated ASR-33. The 8/L I've had running for a while now, but I've
only recently taken the time to go over the ASR-33 it came with. It was
a bit dirty but it's cleaned up nicely and I've got it humming along
nicely now. (With the exception of the paper tape punch, which is going
to need a bit more work.)
At any rate -- this ASR-33 was outfitted with the DEC "reader run"
modification, and it does not appear to be functioning -- with the
teletype in "Line" mode, the reader switch set to "Start," and with
the
8/L running the RIM loader the reader does nothing. (It also does
nothing when set to "Start" in "Local" mode, but I'm unsure if
that's
expected or not...)
With the cover off, if I manually toggle the "trip coil" at the rear of
the unit the reader runs and the 8/L receives data (and it looks to be
correct). I've verified continuity between the RELAY+ and RELAY- lines
from the W076 in the 8/L all the way to the reader run board, and I'm
measuring 15V between the two.
It's about here where my naivete around analog electronics starts
kicking in and I'm unsure where to go from this point -- any suggestions
are much appreciated.
Thanks,
Josh
--
Met vriendelijke Groet,
Simon Claessen
drukknop.nl