On Thu, 1 Jul 2004 00:45:56 +2500 (BST)(!) Tony Duell wrote:
> Actaully I'm more likely to suggest yoy resolder that darn
> dry joint, and
> go over others in the area. Preferably before soemthing in the sense
> circuit goes open and the output jumps to 15V or whatever!
>
> -tony
>
Bad solder joints in power supplies bring back memories... cooked ones...
My Superboard 2 (to be exhibited at VCF East) came without a power supply,
so this intrepid owner got to build his own. Any bad solder joints are the
responsibility of exactly one party...
I kludged a STD-Bus 32K CMOS RAM card (using 16 of 6116 2kx8 parts) onto
the Superboard, and used a free set of 4 size-F NiCad cells as a battery
backup. Size F is used to make the 6-volt lantern batteries, by the way, so
the current capacity of my backup was calculated to keep the board running
without power for roughly 7 years, disregarding internal battery leakage. 7
Amp-hour NiCads can also start a fire in milliseconds: with that in mind, I
placed a service switch in series with the battery so I could take it out of
circuit if I had to fix something. Clever, right?
One day (about 1985) the power supply became intermittent and I had to
dive in to the Superboard's case to identify the problem and correct it.
Awake and alert at the time, I pulled the AC plug, then switched off the
battery. Disassembling the machine, finding the solder joint and
reassembling took me longer than expected, so it was around midnight when I
was ready to power everything back up.
Here's where circuit details caught me: my main charge circuit for the
NiCads was limited to about 5.1 volts - perfect for a 5-volt RAM card.
However, NiCads should have a "trickle" charge of 0.1-1% of capacity to keep
them healthy: for a 7Ah battery, that's 7mA (drawn from a 12-volt supply via
a resistor). This is important, since the RAM card, idle, draws 0.1mA.
Without the battery to absorb the trickle current, the RAM voltage goes
(way) out of spec. (Fortunately, the Superboard had a completely independent
regulator...)
I plug in power, then realize with horror that the battery's out of
circuit and the trickle charge is feeding 12 volts to the RAM. Yank cord.
Check everything out to see what damage was done - couldn't find anything
seriously hurt. Whew.
About 2AM, I plug the cord in again - Moron! The battery's STILL off!
This time I found 2 RAM chips shorted (and snipped the trickle charge
resistor out of circuit). It took me another week to find the last victim,
a 74HC245 bus buffer with its ground bond wire blown internally - no
physical evidence - and CMOS protection diodes on its I/O pins kept the chip
working as long as it had enough logic-0 inputs to work the logic-0 outputs.
When the Superboard READ 0FFh from the RAM board, the '245 starved and I got
errors...
In hindsight, there were so many ways to prevent that...
Bob Maxwell
Hi all,
I decided to power on my MicroVAX 3800, after it's been idling for a couple of
years (unfortunately due to lack of time on my part), only to find that it's
not booting properly. The LED display on the cover/patch panel sits saying 'F'
(apparently "Waiting for CDOK"); nothing else happens. Anyone got any ideas as
to what may be wrong, or if it's fixable?
If not, there's a KA655 on eBay for 20EUR (currently), or 39EUR BIN - is this a
reasonable price?
Dan
--
He who sneezes without a handkerchief takes matters into his own
hands.
I'm looking for the EMS rom for the HP-85A. Or better yet, has any progress
been made in the project to clone the HP programmable rom module?
Jay West
---
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Ok, I'm finally catching up with VCF East planning. Sorry for all the
delays.
The dates for VCF East are July 16-17 (FRIDAY and Saturday). The location
is Burlington, Massachusetts, at Sun Microsystems' corporate campus. Sun
is sponsoring the event.
Those who have already submitted exhibit entries have just been replied
to (Tom Uban: you probably won't get my e-mail due to spam blocks but rest
assured you're in there).
Current exhibitors can be seen on the VCF East 2.0 exhibits page:
http://www.vintage.org/2004/east/exhibit.php
We've got ten exhibitors so far (2 pending approval) which is a good
start, but I'd like to see more. So if you're planning to exhibit at VCF
East, now's the time to register.
I'm also putting together the speaker roster. If you have someone you'd
like to suggest as a speaker, or you'd like to give a talk yourself,
please e-mail me.
Things will start moving fast from this point forward. The next VCF
Gazette will be coming out soon with more information.
Hope to see you all at VCF East 2.0!
--
Sellam Ismail Vintage Computer Festival
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Hi Marvin & Jules
Yep, that is the polymorphic CPU card. The CPU is a 8080 and
the 4 sockets above the CPU are for 2111's. The three sockets
take 2708's. It is missing things like bus buffers. Marvin
or I can get you a schematic. If you get one of the vidio cards
and a parallel keyboard, you can actually do a small amount
( with the 4 2111's as RAM ). The two socket at the upper
right go to a serial buffer card and a cassette interface card.
I do have the schematic for these as well but the cassette has
a couple of chips that may be a real bear to find.
I also have the ROM monitor code and TINY BASIC that will
run on this card.
Dwight
>From: "Marvin Johnston" <marvin(a)rain.org>
>
>
>I *think* this is a Polymorphic CPU card, but I can't get to any of the
>cards right now to make sure. IIRC, IPC was the company name that was
>associated with Polymorphic Systems, and that name appears on most, if
>not all, of their S-100 cards. In checking some of the Polymorphic
>engineering drawings, I.P.C. showed up the one PC Board layout I found.
>
>Jules Richardson wrote:
>>
>> On Thu, 2004-07-01 at 20:16, Jules Richardson wrote:
>> > Random S100 board in the pile. Says "(c)1976 I.P.C" on the underside,
>> > but there's nothing else by way of identification.
>>
>> I've put a small photo up at:
>> http://www.moosenet.demon.co.uk/temp/comps/s100/unknown_s100_sm.jpg
>>
>> any ideas?
>>
>> cheers,
>>
>> Jules
>
In the not too distant future I should be starting my 11/45 restoration
project. In anticipation of that....
My 11/45 front panel has a number of switches that dont work. The normal
failure mode of the switch covers breaking is not the case here. My problem
is the actual switches on the PCA under the switch covers. They have
disintegrated the way I've seen C&K switches do before. I went looking for
C&K switches a long while back for an unrelated project and had trouble
finding them.
I could just locate a whole new front panel, but those get a huge premium on
ebay. I'd just rather find the switches and solder new ones in place. Does
anyone know exactly what switch the 45 uses, and where a source for them
might be?
Thanks in advance,
Jay West
---
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> Next question is, does anyone want it for any homebrew projects?
If it's not already taken, yes please.
Lee.
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Random S100 board in the pile. Says "(c)1976 I.P.C" on the underside,
but there's nothing else by way of identification.
No obvious function for the card, but there's a few empty sockets on the
board though:
1 x 40 pins (CPU?)
4 x 18 pins (memory?)
3 x 24 pins (ROM?)
Any ideas?
ta,
Jules
I picked up one of these from a surplus store yesterday. Unfortunately
soembody removed the system card that contains the special version of
Windows and some other software from it. Does anyone have an xtra system
card or the external floppy drive for one of these?
Joe
looks to be a single board computer that a company did for some type S100 based controller. A CPU, some ram, some rom, I/O and 16 pin dips connectors to send the I/O for testing. The 40 pin chip is probably an 8080 (could be a Z80). My best guess anyway brcause I don't recognize the IPC ID.
best regards, Steve Thatcher
