29 Apr
2011
29 Apr
'11
2:02 p.m.
I took the plunge and put in the CPU modules (M7133 and M7134) into the
PDP11/24. The machine powered up and the DC ON light came on, suggesting
voltages were in tolerance. So I connected a terminal and got an ODT prompt.
I then tried to run a basic diagnostic (using the ODT command 165000G). It
came back to the prompt and I was just entering another command when I heard
a vague click and the machine powered off. I cannot power it on now.
Previously after connecting it to the mains I would hear a slight click, but
I don't even hear that now and turning the key will not even start the fans
running.
Oh $deity...
I am actually not too suprised about the fans if nothing else is working.
As I mentioned earlier, the fans run off a 36V DC output from the memory
switch-mode PSU. So if everythign is dead, the fans don't run either...
However power is getting to the big capacitors because I can see that with
my multimeter, so it is not the external fuse or the circuit breaker I
think. Presumably some internal fuse has gone, I will leave it to discharge
I don't remember any inernal fuses...
I am going to have to look at the prints, but from what I remembr,
there's soem control circuiry on the leftmost PCB in the PSU unit. This
is powered form a small SMPSU circuit. I think I would chekc that that is
gettign power first. Pehaps solder som wires ot the power pins of one of
the TTL chips inthe control section, put the PCB back in place,
conenct said wires ot a voltmeter, attempt to power up and see if you get
5V to power said TTL chip.
-tony