6 Jan
2009
6 Jan
'09
1:09 p.m.
I managed to coax my PDP-11/05 back into life today and ran a few simple
programs on it successfully.
As a result a few questions for the experts out there:
1. To get it up and running I had to replace its two fans both of which
had failed which I did by scavenging another 11/05 chassis I have.
Does anyone have any tips on reviving failed fans? Both spin freely by
Hmmm... Normally they suffer from bad bearings, although I don't think
this is the problem with yours.
Most fans can be dismantled. I've come across 3 main types of assembly :
A cap in the centre of the rotor, on the opposite sde to the label,
retained by a circlip. Remove this, then take out any felt pads/waskers
and remove the small circlip from thend of the (fixed) spindle. The
rotor/blades then lifts off.
A similar cap in the middle under the label. Often this cap is flexible
plastic and is retained by the label. After removing it, there's thee
circlip as above
2 screws under the lable. In this case, free the wiring/tag block first.
Then remove the screws and lift the hosing off the motor/blades. On the
top of the motor, you'll see a sirclip. Remove this, then lift the stator
out.
In all cases make sure you know where all the washers go. Some are
special types (I've seen bonded fiber/metal washers with flats on the
centre hole, for example).
hand but when powered one hums heavily and the other
reluctantly and
somewhat noisily spins up (if kick started with a screwdriver). If
This sounds, alas, like winding problems. I've never tried to rewind one....
recovery is impossible can anyone suggest suitable
replacements? The
current ones are labelled Super-Boxers
IIRC, the 11/05 fans are pretty standard (unlike the 35V 70Hz fans used
in te 11/44...) so you can probably get something new from a good
electronics shop. The important thigns are the physcial size and the
voltage rating -- IIRC you need a 115V AC fan here (even in Europe, you
use 115V fans, they're run off the primary of the mains transformer
acting as an autotransformer.
[...]
3. At the moment the machine has 16KW of core (2 x 8KW
planes). This
together with the CPU fills all but the last slot on the Unibus (its a
5inch box so only 9 slots). I'd like to fit a DL11 so that I have some
serial comms and ideally an RX11 as well so I can hook up my RX01 drives
You have a console serial port built into the CPU board set. AFAIK it's
current loop only (which is a bit of a pain), it's wired to the 40 pin
Berg header on the back of the cabinet.
and boot RT-11. Can I make use of the 9th slot or does
this have a
special purpose? There is a lot of wire wrap going to slot 9 so I'm
guessing its not suitable.
AFAIK the 9th slot is just a standard SPC slot and could take either a
DL11 or an RX11. Of course you can't put both in at the same time.
What you can't do is take out one of the memory board sets and use those
slots for peripherals. The wiring there is totally different. There was a
backplane which took the CPU, one memory board set and, IIRC, 4 SPC
boards. But that's not the backplane you have.
-tony