> From: Jerome H. Fine
> I have ... some PDP-11 hardware manuals, but probably most are already
> in PDF files at bitsavers.
Any chance you could check to see if you have something that's not online?
If you have more than a few, you probably do have some that aren't online.
If you whip up a list of what you've got, I'd be happy to check it for you.
Noel
As I've periodically posted, my 8/A has an intermittent power supply problem
(Power OK light and signal line flickers, so the entire system is confused.
Throwing the DC breaker and resetting it will often make the problem go away
for the rest of the evening). It's slowly getting worse, to the point where
tonight the Power light wouldn't come on at all. It's not the breaker
itself. So I decided to put the G8018 regulator assembly on the extender
card.
However, when using the extender, the DC breaker would immediately trip! I
tracked it down to the +5 volt crowbar being triggered. Careful examination
of about four different schematic pages shows a connection on the backplane
between edge connector pins BP2 & BR2 and the multiple +5 volt busses on
edge conn C. If you look at the schematic, BR2 is a test point but BP2 goes
to the anode end of the 5.7 volt zener that sets the crowbar voltage (its
cathode is connected to +5) and through a 10 ohm resistor to the crowbar SCR
gate with 100 ohms to ground.
This makes *no* sense because that connection shorts out the zener, so as
soon as the +5 comes up, 100/110 of the +5 is applied to the SCR gate, so
naturally it fires!
A close look at the G8018 provided the answer. There is half a finger etched
on BP2 which is also fully connected to BR2. (See picture) Looks like a
drafting mistake to me.
The Douglas extender board has sufficient depth in its female connectors
that the partial finger of BP2 made contact and caused the crowbar to
trigger as described. Cutting the "web" between the fingers fixed the
problem.
Naturally the intermittent flicker is gone for now, and I doubt it was an
"almost" connection to the SCR gate because once it fires, the +5 should
drop to near zero and trip the breaker, which has not been the case (except
with the extender card). But at least I have the regulator on the extender
card so I can start measuring when it comes back!
http://s1181.photobucket.com/user/DrCharlesMorris/media/PDP-8/P09-26-15_20.…
>>> As I mentioned in another response, I truly dislike SQLite, based on my
>>> experience with it on my Garmin GPS.
>>
>> I'm still not sure why - my experience has been very good. What bad
>> experiences have you had?
>> ~~
>> Mark Moulding
>>
>
> My Garmin has had data integrity issues in its database. Plus, lack of
> *convenient* tools, and having to rummage around here and there to find
> them.
>
> On top of that, this will be part of an online web app some day, so
> having the database in the address space of the web server is probably
> not a Good Thing.
I haven't used SQLite in an embedded environment yet. I wonder if it tends
to thrash certain areas of the data file (which would cause flash wear
problems). I appreciate the data point...
And yes, SQLite was not intended for a high-volume multi-access environment,
and my experience is definitely from embedded up through low multi-user
local network applications. I'm sure there are many good reasons why MySQL
has become the standard for web server applications. I originally
understood - perhaps erroneously - that this was to be a smallish, local
application, and for me (and the smallish types of systems I tend to build),
I'd prefer to avoid the headache of administering the MySQL subsystem.
But I stand by my statements about the separate, non-editable keys... :-)
~~
Mark Moulding
I wanted to share this because it's pretty neat:
https://www.youtube.com/watch?v=0BHIknNa6Eg
It's a ~6 minute tour of a home automation system from the 1980s that
features graphical floor layouts and touch screen programming. The system
is built into the house.
--
Sellam ibn Abraham VintageTech
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I have a BA11K power supply out of a pdp 11/34 that has frozen up fans.
They are frozen up pretty bad. I heard from another list member here they
are repairable, any advice on how to do so?
--Devin
> From: tony duell
> They would never take being straightened, the metal is partially
> fractured already.
Ah. OK. Well, a later poster mentioned a possible source of new feet - I had
assumed you wanted exactly identical ones, which may not be available, but if
all you want is functionality, you can probably find that from the sources
they provided.
> I have found a little 4 slot Qbus box with 3 swtiches on the front,
> these seem to be the same mechanisms behind the toggles.
Yes, they are: I fixed an 11/05 front panel with switches sourced from one of
those 11/03 front panels. I hated to do it, but the 11/03 panel was a spare,
and as you say, if the switches ever re-appear, I can repair it.
Noel
> From: tony duell
> 2 of said feet got bent at right-angles (!)
Hammer them straight, and clean up the threads with a die. Those outriggers
are unobtainium, so I can't imagine the feet are much better.
> switch mechanisms for the PDP11/45 front panel. I have the toggles
> (thankfully), I need the switches
Now you're really into unobtainium territory. We've been moaning about the
inability to find these for a while now. All the early 11's (except the
11/20) use these - 11/05, 11/40, 11/45, etc - and a bunch of us need them,
but nothing doing.
Noel
