29 Apr
2011
29 Apr
'11
12:03 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.
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
and take a look tomorrow to see if I can find an internal fuse. Any other
ideas as to what this might mean?
It was going so well..
Regards
Rob
29 Apr
29 Apr
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
4:25 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: 29 April 2011 22:02
To: cctalk at classiccmp.org
Subject: Re: H7140 PDP11 PSU
power
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 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
I will add some diagnostic wires to the board as you suggest, I don't
remember a lot about TTL chips, is there a convention about which are the
power pins?
In the meantime someone else told me that the click I would hear when
connecting to the mains (before switching it on with the key) was some kind
of relay. I don't hear that anymore, would that help to isolate the problem
at all?
Regards
Rob
30 Apr
30 Apr
1:23 a.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Rob Jarratt
Sent: 30 April 2011 00:25
To: 'General Discussion: On-Topic and Off-Topic Posts'
Subject: RE: H7140 PDP11 PSU
> -----Original Message-----
> From: cctalk-bounces at classiccmp.org [mailto:cctalk-
> bounces at classiccmp.org] On Behalf Of Tony Duell
> Sent: 29 April 2011 22:02
> To: cctalk at classiccmp.org
> Subject: Re: H7140 PDP11 PSU
>
> >
> > 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 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
I will add some diagnostic wires to the board as you suggest, I don't
remember a lot about TTL chips, is there a convention about which are the
power pins?
In the meantime someone else told me that the click I would hear when
connecting to the mains (before switching it on with the key) was some of relay. I don't hear that anymore, would that
help to isolate the
problem at
all?
Regards
Rob
I have extracted the leftmost board, which is a 5413605, according to
printset that is a "bias and interface" board. Looking at where it is
mounted in the PSU, it *appears* to be connected to the fan spade
connectors, so would be involved in powering the fans (the motherboard
printset would seem to confirm that). There is a 74LS00 chip on it to which
I will attach wires to Vcc and Ground so I can test if for power. I followed
the Vcc track on the back of the board and it does not appear to go to the
boards "backplane" connectors. I tried to read the printset to see which
pin(s) on the connector the power comes in on but I don't understand the
conventions about which pin is pin 1 on the connectors, so I can't at the
moment add wires for that. I will go ahead and add wires to the 74LS00 in
the meantime.
Regards
Rob
4985
days inactive
4986
days old
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ard＠p850ug1.demon.co.uk -
robert.jarratt＠ntlworld.com