> From: tony duell
> it's quite possible they started off at the top end of that range, have
> deteriorated over the years, and are still within spec. Of course
> nobody can prove that (unless there are records of the values meaured
> 50 years ago)
Well, I don't know about 50 years, but I know some of the restorations (where
people said they checked that their electrolytics were still withina spec)
were a while back, so _iff_ they have records of what they measured, it would
be interesting to see if there's any drift from then, to now. But I have no
idea what numbers they have, they'd have to speak to that.
> I have no idea what was measured. The capacitance value is not the
> whole story by any means. In fact the most important thing most of the
> time is ESR
Again, I have no idea what they measured, so they'd have to respond on that.
Noel
>
> Date: Mon, 20 Jul 2015 14:11:46 +0000
> From: tony duell <ard at p850ug1.demon.co.uk>
> Subject: RE: PDP 11 gear finally moved
> >
> > Replace - yes, *especially* if you don't have a big budget. Aluminum
> > electrolytic capacitors are CHEAP and easy to obtain. Replacement
> > semiconductors by comparison are expensive and can be quite difficult to
> > find.
>
The RICM ignored the sage advice from experts and reformed the
electrolytics in the PDP-12 that we are currently working on. This decision
was based on our past experience on other restorations, the lack of
replacements in the same physical size, and the very high cost of the
replacements. So far the system is behaving nicely.
We have had several spectacular failures of the AC caps with the
ferroresonant circuit in DEC power supplies. We regularly replace the AC
caps because they are available and inexpensive.
--
Michael Thompson
As I mentioned previously, I took some time off from working on the
MEM11 for the past several months.
I had some time over the past few days, so I spent it working on the
simulator.
Right now all of the J1 instructions seem to simulate properly.
Everything related to the basic simulator
also seems to be functional. I still have work to do to write code for
the simulated I/O (it's all stubbed
out at the moment). The way that I'm implementing the I/O, is that it's
pretty modular. All of the
fundamental code structures are there, I just have to write the
"handlers" for the particular I/O devices.
I wrote the majority of the J1 simulator to be H/W agnostic (as far as
the I/O is concerned), the I/O
at this point will match what I expect to be in the actual MEM11 H/W.
Here's what the simulator currently supports:
- All command functionality is present and functional. These are the
way that one interacts with
the simulator. The commands include things like:
- loading files into J1 memory or FRAM
- dumping memory locations from J1 memory or FRAM
- modifying memory locations in J1 memory or FRAM
- setting, listing and clearing breakpoints
- starting execution
- single stepping execution
- dumping the data & return stacks
- starting and stopping instruction tracing
- All of the J1 instructions now seem to execute correctly (lots of
typo's and other subtle bugs)
- Exceptions work now. This allows the J1 program to do something
"silly" and the simulator
won't crash (had enough of that already while I was debugging the
simulator!).
It'll report what the J1 program did that was "silly" (ie
unaligned memory accesses, etc).
- It also contains a reasonable "help" system.
I've written an instruction test program that tests out all of the J1
instructions and it is "self checking".
That is, it will throw an exception (unaligned address) if the result of
the instruction test isn't what
was expected. To determine what failed, I look at the address where the
exception occurred and
reference the test program listing to determine which test failed. I
verified that it is indeed operating
correctly by hand checking via the instruction trace file that it was
doing the "right things".
I had originally started debugging by single stepping through the
program but after the test program
grew to over a few dozen instructions, it became too tedious for me to
ensure that I was accurately
verifying the instruction execution. This is where the instruction
trace file became invaluable.
The next thing to do is to work on the simulated I/O. Once I'm
confident that all of that is working
then I can go about debugging all of the code I've already written for
the MEM11 itself. The simulator
should give me a pretty good environment for debugging, especially when
compared to the actual HW.
Oh, and of course everything (simulator, MEM11 firmware and tools for
the build environment) are all
written in forth. ;-)
TTFN - Guy
Folks,
With the help of my local rescue buddy (Jeff) we had a pretty busy week
rescuing a big chunk of things from basements.
(and saw a lots of other interesting things... a 90% assembled Rutan EZ in
one basement and a very cool, oscilloscope that
would probably have have had a lot of folks drooling...a KS-15512-L5 made
for Western Electric by Polarad Electronics
...we DID ask about it, but so far he's holding on to it.. but we did get a
couple of tube radios for a local AHCS member)
I had to pay for some of the material (and both had a "take it all/most"
sort of requirement) so my goal is to at least cover
my costs (the Wife lets me keep doing so if I keep it at a $0 or positive
number... and so far, I have...amazingly enough).
Keep that in mind... this isn't going to be a give away... but I'm not
trying to make a living here, just didn't want to see stuff
end up in the scrap heap. And if I can keep a couple machines. And to be
honest, after looking thru all of this, I'm simply
not going to have time to restore all of it... the project list is long
enough...
Here's the list:
1x HP 85 B (plus 3 modules, I'll have to check them out in further detail)
1x HP 9816 with 9131 dual disk drive
4x Otrona Attache's (and a huge plastic tub of original replacement
parts... a first look indicates enough to build at least 1 more machine)
Some of these have the 8086 accessory board that allows it to run MS-DOS
(along with the CPU it normally runs with it's Z80)
1x Wang Model 370 Calculating System with a Model 372 Data Storage System.
2x SOL 20's (and a couple of Micropolis 720 DSDD blue drives for one... )
1x Zenith H-19 (this may have been updated to a newer model, I haven't dug
into it much)
1x Mitsubishi MP-2010 Laptop
And there is a pile of SW... believe I have at least a boot disk for each.
I've not tried to power anything up (it was a busy week driving around town
picking up stuff) except for one Otrona which did
seem to have some life, but didn't boot or show anything on the screen.
But I haven't checked inside anything so could be simple
(And yes, I only tried powering it on because of the HUGE box of spare
parts... so was willing to have something emit the magic
smoke.... the curiosity simply was too much :-) ) There are a few assorted
terminals and various spare parts that I got as well.
If you're interested in anything ping me... and we can see if we can work
out details/trade/etc. Pictures can be sent
or posted... again, not enough time to get that done yet.
One other thing, I'm hoping to get to VCF MW (or at least be able to have
someone who is going carry some things)
so if you're going to be there, I we could use that to save shipping. I
don't have a problem shipping either.
EarltheSquirrel.
> From: Guy Sotomayor
> I took some time off from working on the MEM11 ... I had some time over
> the past few days, so I spent it working on the simulator.
Excellent news!
> Right now all of the J1 instructions seem to simulate properly.
I had to go hunt up your original message:
http://www.classiccmp.org/pipermail/cctalk/2015-January/002879.html
to refresh my memory as to exactly what a 'J1' was!
It was interesting to re-read your original message; I and a couple of other
people are looking into doing a QBUS card to provide access to modern
non-volatile storage (SD cards, USB thumb drives), and in discussing the
internal design, we'd planned on an FPGA, and a separate micro-controller.
Your concept to have the 'micro-controller' _in_ the FPGA is interesting! The
only problem, from our point of view, is the 'limited' number of FPGA pins
(the QBUS interface alone is ~50 pins) - at least, without going to a BGA
part, which we view as undesirable.
> Everything related to the basic simulator also seems to be functional.
I'm curious as to your reasoning in doing a custom simulator (OK, it's all
fun :-). I do understand having _a_ simulator (writing all the software
involved on the card will be much easier if you don't have to deal with a
flaky/new hardware), but since the J1 is in the FPGA, couldn't you just use
the FPGA simulator? Or is it too slow to emulate a good-sized J1 program?
Noel
PS: When we get down to detailed design, we'll have to get the specs on your
light panel interface; we'd like to be able to drive the same light panel
(for exactly the same uses :-), to avoid re-building the wheel.
Hi Guys
As usual I try to keep you updated on front panel
progress.
(Always supposing I know where I am!!)
I now have _prototype_ white seperation artwork for four front PDP8 panels
1. pdp8/e Type A
2. pdp8/e Type B
3. pdp8/f
4. pdp8/m
I am doing all four together as they share the same basic plexiglass panel.
There's a lot to do to to get to the point they can be silkscreened.
I have put all four as they now stand in a file (.svg) and if you email
me direct I'll send it to you.
Rod
I have an IBM 5120 desktop computer to give away, but it has no circuit cards, so it won't work as-is.
Danger- it weighs 100 pounds.
Located in Orange County, CA 92656
Dave Tumey sent us a new rubber hammer for the Teletype. This is the part
that pushes the print drum against the ribbon and paper to print. These are
newly molded parts that have not been available for decades. Works very
nicely.
The ripple on the power supplies is still going lower as we put more run
time on the system. The power supplies are now within spec.
Warren wrote a better memory checkerboard program that shows the bits that
were being picked up or dropped in the MQ register. We tried adjusting the
STROBE FIELD 0 delay about +/- 100nS, but there was no setting that
resulted in completely working memory. Changing the delay did change the
location and number of bits that were picked up or dropped. Since the
failing addresses were all above 1000 we tried replacing the G221 modules
in slots C07 and C08. There was no change. We suspect that we have a
problem in the inhibit circuits.
Warren made an Arduino based programmable baud rate generator that works
for both serial ports. After some debugging, it works nicely.
The donor dropped off the work table that goes in front of the PDP-12. We
need to loosen the rusted feet so it will fit under the front panel.
--
Michael Thompson
Greetings folks. I'm on a mission to get some replacement bulbs for my
2100A/S machines. The official part is 2140-0364 (38 of them per machine).
Google appears to indicate that an identical replacement is CM7361-200. One
of my old parts donor 2100's has both OL-783BP and OL-783BPC, but I don't
know if those are completely identical and the previous owner may have just
put something "close" in them instead (particularly important is estimated
life, the 2140-0364 are around 10,000 hours I think, other replacement parts
appear to be a lot less life-hours).
I'm not looking to replace just a few bulbs, as I have a few spares on hand
already. I'm looking to buy around 50 or 100 to just have inventory, and in
case I decide to fully restore the two 2100's that are currently donor
machines and get them fully running.
Has anyone already found a good source/price for these? Given the number of
bulbs per machine, cheaper is better :) I may have to go to one of those
bulk purchase parts places, in which case I'd probably need an order of 1000
or so. If I have to go that route, anyone with 2100's want spare bulb sets
and willing to go in with me on it?
Just as an FYI for HP bulb related stuff...
I just purchased 30 bulbs for my 7970E tape drive status lights. They were
$0.28 each bulb (sold in 10 packs for $2.81). Those were:
Eiko - 382 mini indicator lamp - 14 volt - 0.08 amp - T1.75 bulb - midget
flanged base
I just put in an order for the HP 2940 rack (these are the older
off-grey/greenish racks) power switch bulbs. those were:
GE & Eiko - 1819 sc1 - 28 volt - 40ma - T3.25, miniature bayonet (BA9s)
Best,
J
