"William Donzelli" <wdonzelli at gmail.com> wrote:
> The caps from 1960s seem to be of little concern, and those from past
> 1970 are of no concern. If the cap decides to die, its going to die.
--
This was not the experience of the PDP-1 team during the restoration of
that machine. Detailed records were kept of every cap that was reformed.
This process took several months to perform.
Blowing up a cap in the machine during restoration was not an option.
Lyle, or one of the other hardware folks would know the details.
I am disappointed at the 'let it just blow up' attitude that has been
expressed on this list so far in the discussion.
The system key can be found on the key rings of many PDP11 enthusiasts.
-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org] On Behalf Of J Blaser
Sent: 08 October 2007 23:59
To: On-Topic and Off-Topic Posts
Subject: Re: VAX 11/750 rescued, alas...
Rod Smallwood wrote:
> Hi
> Fear not all is not lost. There's tons of modules around but not
> that many cabs.
>
Yes, you are absolutely correct! The more I think about it, the more
glad I am to have even this empty chassis. Definitely harder to come by
than the modules that are missing.
A few good souls have already stepped forward offering some help with
the boards, so this revival might be less difficult than I anticipated
at first.
> In the picture of the Qbus board it appears to be sitting on the
> module config diagram.
> As it is pre printed and not filled in by hand its probably a standard
> system.
> That will give you a list of the boards.
>
Yup, I went through that last night. There is another label that was
inside one of the front cover plates that does show a list of modules
penciled in. So I believe I now know what the original configuration of
this system was.
I've come up with a minimum list of boards, and a wish-list of the
boards that were originally included. Looks like the the mass storage
was hung off of a UDA50, and some tape devices on the SI 9700 board
(which I still am completely ignorant of).
I have a couple of Fuji SuperEagles and an RA81, so I'll be on the
lookout for SDI and SMD interfaces for the rebuild. I just hope the
Fujis and RA81 are functional when the time comes!
> Note of caution do not try to turn it on. The power supplies will need
> some work. You need to reform/replace any electrolytics.
>
>
Roger that! I'm a firm believer in a full chassis cleanup, capacitor
reform, and separate PS checkout before every hitting the big switch on
the front! ;-)
Oh, yeah, that reminds me...I've got to locate the 'vending machine'
power-switch key for this thing. Anyone know if it is a fairly standard
key?
> The case will clean up well and you can start off by getting the PSU's
> working and getting the list of modules together. Disk drives would
> have been in another rack I think.
>
This looks like it'll be a more lengthy revival than any that I've done
up until now, which have been mostly qbus PDPs and uVAXen. A great
winter project!
- Jared
So, it seems to me that there is a decently sizable demand for 1541-III
parts. I asked the creator of this thing if he plans to make PCBs any
time soon. He said "no". But he left all the design files, firmware, etc
on his website for anyone to use. So, how about a group buy?
--
David Griffith
dgriffi at cs.csubak.edu
I believe it was Chuck who was asking where to find TMS9900 and TMS9995
chips.. The TMS9900 is available from Unicorn Electronics for
$34.88 each. See -->
http://www.unicornelectronics.com/monthly.html
Cheers,
Bryan
Its not so much the age of the system more how long it is since it last
ran.
As minimum isolate the positive terminal and put a meter on ohms range
across it.
As the capacitor charges the resistance will rise.
If it does then good if not or goes up slowly then change the capacitor.
I rang our old (now retired) DEC branch field service manager and he
said "Turn on a 750 stored for years and with no load on the PSU .. Sure
use a pole about twenty feet long!!"
Rod
-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org] On Behalf Of Patrick Finnegan
Sent: 08 October 2007 19:29
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: VAX 11/750 rescued, alas...
On Sunday 07 October 2007, Rod Smallwood wrote:
> That will give you a list of the boards.
> Note of caution do not try to turn it on. The power supplies will need
> some work. You need to reform/replace any electrolytics.
11/750s aren't that old (early 80s), and shouldn't need reforming. It
appears that William Donzelli agrees with me, and I'm sure he has more
experience with this than I do.
Pat
--
Purdue University Research Computing --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
> I think
> Will's implying that the need to reform caps that new is not necessary,
> because there's no data available to say that it actually does any good...
One though occurred to me just a few minutes ago.
Most failures in capacitors - actually almost all pre-IC components -
can be boiled down to impurities getting into the innards of the part
thru failing seals. This is documented in military and trade rags, as
they found out in the jungles of the Pacific during World War 2. With
capacitors, the problems seem to be the dielectric (oil) getting out
(see my previous post concerning Vitamin Qs), or moisture getting in.
Either way, the dielectric is poisoned near the weakest part of the
cap's structure - the edge of the foil, specifically where the leads
connect to the foil.
I can not see where reforming an electrolytic capacitor will do any
good for the seals. If the seals are drying up, cracking, shrinking,
expanding, or in some way not meeting spec, the crap is going to get
into the innards of the capacitor and lead to a failure. Other than a
complete rebuild, I doubt any seals can be repaired. And if you are
going to do a complete rebuild, you might as well run the cap until it
fails.
And unlike an inductors that can be baked to drive off moisture,
capacitors do not do well in the oven.
--
Will
> From: dgriffi at cs.csubak.edu> > On Sun, 7 Oct 2007, Tony Duell wrote:> > > I can rememebr what 4 are :-)> >> > 1) An old RS23 breakout box. Real slide-switches to open all the wires,> > and 2mm sockets for cross-patching. The main signals are monitored by> > transistor-driven filament lamps, the whole thing is mains-powered,, said> > PSU also prvides +12V and -=12V outputs for forcing handshake signals> > ARRGG!!! You've provoked me into building a banana-jack breakout box!>
Of course if you make one, put all the connector combinations
on each side. Also put an extra connector on it that can be
used to snoop the data in progress between two machines.
One can usually put two receivers on a single drive.
I've used this method to analyze unusual protocols in the
past. It is handy.
_________________________________________________________________
Climb to the top of the charts!? Play Star Shuffle:? the word scramble challenge with star power.
http://club.live.com/star_shuffle.aspx?icid=starshuffle_wlmailtextlink_oct
Having got the Mitac A2 clone up and running (checked out the 80-column output
today and that was fine - only casualty in the whole machine was one cap that
had gone high-ESR), I've dug my Apple /// out of storage...
Disk ]|[ question - should the ribbon cable to the internal drive be plugged
into J2 or J3 on the drive's analog board (does it even matter)? A long time
ago I disconnected mine as a precaution; the drive began eating disks, but I
didn't have time to get to the bottom of it at the time - I suspect it just
needs a good clean.
I can't for the life of me find where I made a note of which socket the cable
plugs into. Normally I leave myself a note somewhere in the machine for things
like this, but for some reason I haven't with this one :-(
cheers
J.
Well, last night, I went and collected my first ever DEC box. It's a
VAXstation 3100/38, bought on eBay for 99p (UK?0.99).
It will be a few weeks until I get it home, and currently, it has no
hard disks, but I'm hoping to rectify that.
I plan to put 2 or 3 old SCSI disks in it - whatever I can find that
will fit. I am sure they'll all be well under 1GB, as I believe that
is a limitation for boot disks. I think I have a couple of 80MB ones
around and maybe a 150MB or so.
The two problems I don't currently have answers for are these.
[1] I don't have a suitable monitor cable. I have a keyboard, 3 mice,
and a DEC 17" mono monitor with a single BNC connector on the back. I
also have a monitor cable, but it's an RGB one - one end is 3
colour-coded BNC connectors, the other is a D plug with three large
shrouded sockets - like the larger connectors in a YB13 monitor cable
but without the standard pins. On the back of the VAX is a monitor out
port, but it's a D connector. Alas the machine is currently 15mi away
or so, so I can't check, but I think it has about 20 pins. Again, a D
connector.
What sort of monitors will a VAXstation drive? I have an old Mac 21"
monitor with a YB13 connector, which syncs happily enough to both PCs
and Macs at around 1024x768, 1280x1024 (at a refresh rate of about
twice a minute) and some Mac res in between - 1152x870 or so. Where on
earth can I find a VAXstation video cable in 2007?
[2] Friends have commented to me that a VAX of this age won't be able
to boot from CD-ROM. Somewhere, I have a hobbyist VMS CD, if I can
find it. It's been suggested to me that the easiest way to install
would be to install VMS onto SIMH on my PC, netboot the VAXstation off
the simulated VAX and install from one to the other. This sounds
moderately hairy to me. I'm not a VMS virgin but I've not used it in
15y or so and I've never installed a machine from scratch - I just did
day-to-day sysop duties.
Is this likely to be correct? That a 3100/38 won't be able to boot
>from CD? If it can, what sort of CD-ROM drive will I need? Do I need
the special 512KB block support that SPARCstations are supposed to
need? I have an old external Apple drive (CD300, I think) that I hope
will do, if I can come up with the right permutations of SCSI cables
to connect it...
--
Liam Proven ? Profile: http://www.linkedin.com/in/liamproven
Email: lproven at cix.co.uk ? GMail/GoogleTalk/Orkut: lproven at gmail.com
Tel: +44 20-8685-0498 ? Cell: +44 7939-087884 ? Fax: + 44 870-9151419
AOL/AIM/iChat: liamproven at aol.com ? MSN/Messenger: lproven at hotmail.com
Yahoo: liamproven at yahoo.co.uk ? Skype: liamproven ? ICQ: 73187508
>
>Subject: Re: TI 990 architecture / was Re: TI-99/4A Floppies
> From: Dave McGuire <mcguire at neurotica.com>
> Date: Wed, 03 Oct 2007 12:48:37 -0400
> To: "General Discussion: On-Topic Posts Only" <cctech at classiccmp.org>
>
>On Oct 2, 2007, at 3:47 PM, Martin Scott Goldberg wrote:
>>> There are really three 99/4 home computers, original with chiclet
>>> keys, the
>>> second and most common with a really nice keyboard and the whie
>>> version that
>>> is really the same thing with a few board level cost reductions.
>>
>> Actually, there's one TI-99/4 and two TI-99/4a models.
>
> What are the differences between them, does anyone know offhand?
>
> -Dave
There are really three 99/4 home computers:
original with chiclet keys the 99/4
the second and most common with a really nice keyboard 99/4a
the white console version that is really the same thing with
a few board level cost reductions. (still 99/4A on the back)
Allison
