On Tue, Jan 25, 2011 at 9:23 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
I am reassembling a PDP-11/44 from parts for the Rhode
Island Computer...
The RA81s won't spin up, so I suspect that I need to replace the
starting capacitors.
I read through the blog - if the motors start spinning as you describe
(I envision you mean for a few seconds; please correct me if this is
wrong) _then_ the drive stops spinning, I doubt it's the capacitors.
If the motors _don't_ start moving when you put the drive online, then
that is one component to examine.
RA81s were at one point, exceedingly susceptible to HDA failure. I
don't recall the specific ECO levels, but some version after "E" used
a different glue than its predecessors leading to particulate
contamination leading to catastrophic failure. ISTR looking for "H2"
or "K2" drives after that disaster.
RA81 drives have a DB25 inside. You can plug a terminal in and run
on-board diagnostics and monitor operations. You can run with the lid
up or lid down (snaking a ribbon cable out of the drive). The molex
connector next to the data connector is to power a small hand-held LED
terminal (I saw one once, used with a high voltage chassis for
particle physics, but the terminal was the same).
Try plugging in a working VT220 and letting the drive tell you what it
thinks is going on. You might find that it's starting to spin up then
not liking what it sees and spinning down.
Oh... just a detail - you mention locked heads - you _did_ pull the
cord to retension the drive belt, right? (for safe transport, the
RA81 has you locking the heads _and_ disengaging the motor from the
HDA by removing belt tension). If you didn't do this step, what I
think may happen is the onboard processor will start to spin the
motor, sense no rotation from the HDA, then spin the motor down and
emit a fault code. Maybe this is what you are seeing?
Reading through your blog, I don't think you will have success with
booting 2.11BSD on your 11/44 with a TU81+ unless you have install
media that knows about that tape controller. The 2.9BSD tapes I have
require an "MS" device (older OSes might or might not require an "MT"
device). Back in the day, there were several incompatible tape
controller types, with different boot ROMs, and your install media had
to match your controller and ROMs (or you had to toggle in the
bootstrap). You can install 2.11BSD using vtserver and a virtual tape
drive though. Also, if you do get real 2.11BSD install tapes, you'd
probably want to be looking for a TU80 and, IIRC, an M7454 controller
card.
-ethan