Tony wrote:
> <88W> ... since
>it's steady, I think we can assume it's correct (at least for the moment).
OK. I'll probe around looking for a resistor connecting high end to +5V.
>What I would _expect_ is the following :
>
...
>
>2) A potential divider across one of the supply rails (probably the +5V
>rail), with the tap to the other input. Possibly a capacitor from the tap
>to ground to provide a bit of power-on delay. The idea is to take the CPU
>out of the …
[View More]reset state when the supply rails are high enough (== when the
>comparator switches over)
The orange 6192 may be that. Its job is just to make sure the
voltage-divider tap comes up slower than the voltage reference?
I'll look for another component (a black one this time) in parallel with
the 6192, to form the bottom end of the divider.
>3) A high value resistor from the output back to one of the inputs to
>provide a bit of hysteresis and prevent the darn thing oscillating. May
>not be essential, but it's good practice to put it in
[View Less]
All,
I didn't get around to the soldering last night. My wife informed
me that we were going to get up at 0400 so the kids could see the Leonid
meteor shower, so I decided to get to bed earlier. Glad I did, it was
spectacular.
I did do some more probing around the mainboard.
>> <88W>...I'll probe around looking for a resistor connecting high end to +5V.
I looked. It doesn't connect to anything nearby, and when I say
"doesn't connect" I mean completely open circuit to everything.…
[View More] Practically
every other connection shows at least *some* conductance to *something*.
Also, I noticed that the other pins from SMD's like this one have a little
trace running off to a microscopic little pit in the printed circuit board.
I assume this pit is where the conducting path dives into the innards of
the circuit board. There's no such trace and pit on the upper right
terminal of this device. I think it really is a no-connect.
On the 6192: I misled you all, I think. My apologies. Although I
remembered the color as "orange", it's in fact a subdued burnt orange, in
contrast to the bright international orange of the tantalum capacitors.
Someone who didn't graduate from the University of Texas might reasonably
refer to it as a reddish brown. :-) Meantime, there is in parallel with it,
just as Tony predicted, a tantalum capacitor (bright orange, with a pip).
One more piece of evidence: all the tantalum caps have, in addition
to the pip, a "+" printed on the circuit board near one end. There is *one*
exception to that, where the pip points toward the power supply and away
>from the "+" on the PCB. It's over near one of the connectors on the back
edge (maybe the SCSI, or 25-pin serial? I forget, but will post good
directions if anyone wants). The "+" mark is not present on 6192's position
on the PCB.
1) Anyone with access to a 4000 VLC mainboard, would you mind checking and
confirming that *all* of the tantalums are supposed to have the pip near
the "+" (and hence one of mine is probably in backward)? Or wait for better
directions, and check just the one that's backward on my board?
2) What's the consequence of having it reversed? Is that cap. probably now
dead?
Anyway, by now I'm pretty convinced 6192 is the lower resistor of a
voltage divider.
I did not find a feedback resistor for the comparator. It still could be
there, but I don't think it's very close by.
- Mark
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> > The tinker gene is alive, but tinkering is indeed getting harder to do.
> > Kit building and ground up projects are very much alive in audio,
> > especially speakers. If you visit www.headwise.com you will see close to
> > a dozen different headphone amp projects.
>
>Is that url right? Looks like that one points to a web portal of
>somesort...
I may need to see a URLologist, try this one
<http://headwize2.powerpill.org/index.htm>
Hi folks:
I recently got two Osborne 1 computers. The first one (blue case) had a
dead power supply -- I fed +5/+12 DC power into the battery connector and
was able to bring it to life, but had no software to test it further. This
one has a double-density option board inside (and drives I presume), as
well as the optional modem.
I also got a second osborne (early beige case), which came with software
and manuals. This one has a keyboard that seemed to have a stuck key.
Turns out that the …
[View More]keyboard matrix has many shorts, not only row-to-column,
but also row-to-row and col-to-col. It is a flex-circuit soft of design,
and it appears to have a silk-screened or deposited metallization pattern
for the matrix. There is an insulating layer of some sort and then a
second metal layer. Anyway, it seems that the insulation between layers
has failed where some traces cross. It'll be a mess to fix, if even
possible. Anyone else have this problem on an early keyboard?
So I plugged the later keyboard into the early unit, and was able to boot
cp/m. I tried to copy the original cp/m disk to a new one, but copy had
read errors on a couple of tracks. I could see some visibly-crappy spots
on the disk surface too, but it did boot fine, and the utils seemed to run
ok. So I formatted a new disk, copied just the system, and then pip'd the
files over. Hmm, no errors on file reads with pip -- does that make sense,
since copy previously found bad tracks? After booting and running off the
new disk, it seems that all command files are working, with the possible
exception of movcpm (which seems to hang the machine, though I am not sure
how it works).
So I finally got the original disks copied, and learned a bit about the
machine in the process.
I fired up the later (double-density) model, but it would not boot from the
single-density disk. Should the DD drive be able to read the SD disk? The
drive was making an odd noise, so it may be drive-related. Is there a way
to boot from drive B? Can I swap the drives, and if so are there
master/slave jumpers, or terminations that need to move as well? On the
early machine, there was a diagnostic mode in rom (ctrl-D at the boot
screen, I think it was), but the newer unit does not respond to that. Were
diagnostics removed from later roms?
I swapped the working power supply from the old unit into the new machine
(yes, I know about the different jumper/harness connections). It worked fine.
Then, I put the non-working power supply into the early unit, and it
started working! I think the original power supply problem in the newer
machine may have been an intermittant in the fuse/voltage-selector gizmo,
which tells the PS whether to expect 115 or 230 -- in the early unit, this
gets hard-coded by the jumper wire on the PS board. Crazy frickin'
computers.
Then I accidentally cracked the brightness trimpot on one, as I put things
back together. Tacked a temporary pot in place while I look for a
replacement. I shouldn't try to do this stuff at 2 in the morning, I guess.
Well, that was sort of an FYI ramble, but any thoughts appreciated. Does
anyone have double-sided software for sale or trade?
thanks,
gil smith
;-----------------------------------------------------------
; vaux electronics, inc. 480-354-5556
; http://www.vauxelectronics.com (fax: 480-354-5558)
;-----------------------------------------------------------
[View Less]
Makes life blow when you have no money, though... Trust me!
Will J
_________________________________________________________________
The new MSN 8: advanced junk mail protection and 2 months FREE*
http://join.msn.com/?page=features/junkmail
Sellam Ismail wrote:
> I believe the seller is being completely disingenuous when he says, "I
> don't have a monitor or the expertise to test it", considering that he is
> selling a monitor with the Sol! Being that it only contains a RAM card,
> this is seller code for "it doesn't work but I don't want to let you know
> that". Dishonest.
>
He says the keyboard lights up when it powers on, so it does also have
the main board (which is where the processor is in a SOL), but …
[View More]still at
these prices you're paying for collectability rather than functionality,
so a non-original memory card doesn't add much value - it is a minimal
SOL, albeit in nice condition.
I'll give him the benefit of the doubt and assume he doesn't realize
that the TV is meant as a display - he probably thought the PL-259 video
connector was to attach a boat anchor or some other exotic accessory. It
seems that a lot of the tech stuff on eBay is sold by people who are
*completely* non-technical - I stumped one seller by asking him what
card an Apple 3.5 drive was attached to - he had trouble "tracing the
wires". Doh!
Ben
P.S. I read in the CCTalk archives that you had Bob Marsh as a previous
VCF speaker .. did you ever put a transcript of his talk on-line, or
maybe have a recording of it available?
[View Less]
There's one that I just saw get unloaded a few minutes ago at Purdue
University Salvage. Looks to be in good condition... except it's laying
outside on its side since they regard big things like it as 'junk'. Well,
if anyone's interested and nearby, drop me an email and I'll get you more
details.
Unfortunately, I don't think it'll last too long outside - they may end
up dumping more stuff on top of it, or mother nature may end up dumping
stuff on top. I would get it myself but I don't have …
[View More]any way to get it,
let alone somewhere to store it.
Pat
--
Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
http://www-rcd.cc.purdue.edu
[View Less]
As mentioned, I just picked up some new machines in Canada...
A gent had saved some National Semiconductor ICM-3216's from a university
lab and was glad to find a new home for them. These are fairly full-
featured little systems designed to showcase NS's 32000 family, with on-
board serial and parallel ports, a SCSI controller with it's own Z80 to
mind the bus transactions, a modest expansion bus, etc. Since these were
board-level products, everything else like cases and drives had to be
built …
[View More]or found elsewhere.
Two of the hosts I received were timesharing systems and are housed in
nicely designed cases custom built from sheet steel. A third timesharing
host has gone elsewhere, and a fourth ICM was later built in a PC/AT clone
case where students could try coding on the bare metal by booting from a
SCSI floppy drive.
One of the timesharing systems powered up and ran just fine before
loading for the trip South.
The icing on the cake was an unexpected trove of manuals that originally
came with all this stuff, including full schematics for the boards, and
two (binary) versions of SysV Unix on QIC tape. I'm still sorting through
all this stuff, which includes a folder full of notes, letters, and some
brochures for different components like disk drives and terminals, mostly
>from 1986.
Eventually I expect to get some pictures up, and depending on where VCF
East is I think I'd bring one along.
--Steve.
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A while back I'd asked for tips on moving machines from Canada down
to the US. Thought I'd answer my own question now that I've done it.
The gentleman giving me the systems (details to follow) wrote me a
note stating that they were obsolete, over 15 years old, and that any
commercial value was less than $100. It also stated that the machines
were a gift rather than a sale, which was the case.
It looked like the US Customs agent wouldn't have bothered asking,
but I mentioned the machines and …
[View More]handed her the letter. Had it been
a trailer-load rather than a couple boxes in the back of the SUV, it
might have been different, but as it was she just waved me through.
--Steve.
[View Less]
Actually there's two SOL's currently on eBay.
The 2nd one is currently "only" $500 or so:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2071406461
The difference being that it has no documentation (which I suspect accounts for
the price difference), and also it only has a single card in it - a non-PT 64K
memory card (I asked the seller if it was PT or not).
In recent history SOL's have sold for anywhere from $490 to $2500!
Documentation also seems to be what has so far driven …
[View More]this Altair to $4K:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2072033128
Ben
Glen Slick wrote:
>At least $1500, ending today....
>
>http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2071171983
>
>
>>From: Sellam Ismail <foo(a)siconic.com>
>>Reply-To: cctalk(a)classiccmp.org
>>To: <cctalk(a)classiccmp.org>
>>Subject: Re: Whats wrong with chip collecting?
>>Date: Sun, 17 Nov 2002 14:04:53 -0800 (PST)
>>
>
>>I suggest the former. Prices for old computers are fairly well
>>established by now. These prices are independent of, for instance, the
>>CPU that may power the computer. For example, if a SOL-20 goes on the
>>market, chances are it could fetch up to $1,200, regardless of whether it
>>had an Intel C8080 on the original Processor Technology CPU board or if
>>it had a Cromemco ZPU with a Zilog Z80 (even a first run Z80). The CPU
>>has no bearing on the valuation of the machine.
[View Less]
