[TUHS] PDP11/34 boot problems, here i am again :)
asbesto at freaknet.org
Tue Apr 15 10:00:37 AEST 2003
some months ago i asked for help booting a pdp11/34 here at
freaknet medialab :)
well, i think now we have a more complete knowledge of the REAL
the M7891 board (128K x 18 bit MOS MEMORY MODULE) have the D2 red
led light turned ON when turning on the CPU !
this means PARITY ERROR on this board :(
checking the board we found 2 problems:
1) a 74LS175 chip named E15 on our schematic diagram, that seem
phisically BROKEN on an edge (there is a fessure on the plastic
DIP package). i can't change it now because i don't have a
soldering station here to do a nice job, but looking the chip i
think it may work...
2) a 5 Kohm 4-resistor bridge named R22 on our diagram, that is phisically
BROKEN. this bridge give +5V on signals named DATA OC L, CSR OC L, OC L
and X ADD OC L. i changed it with a 4.7Kohm 4-resistor bridge, without
any result. (maybe the 74ls175 is really broken :)
an other ipothesys may be: some electrolitic capacitor in short circuit.
we had this problem on a decwriter III ! :)
the real problem is: if we aren't able to repair the M7891 board, where
can we find a "new" one ???
can somebody help us ? it's a shame for us to have our pdp11/34 offline :((
any help is appreciated ! *:)
[asbesto : freaknet medialab : radio#cybernet : GPG key on keyservers]
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