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View Full Version : Donner 3500 - Early Portable Analog Computer



billdeg
May 29th, 2009, 08:29 AM
Here is my page for the Donner 3500 computer. I have not yet cleaned it yet, or tested the tubes. It's similar to the Heathkit EC-1, except that the amplifiers are stored on cards one can remove to clean and repair. Kind of cool.

http://vintagecomputer.net/browse_thread.cfm?id=247

Bill

billdeg
May 29th, 2009, 08:35 AM
Question

If you look at this picture, and the tube silkscreens (for example)
http://vintagecomputer.net/donner/donner_3500_amplifier-front-1.JPG

Is there a way by looking at the tubes or other components from the late 50's early 60's to id the date the components were made, similar to the later TTL chips have a date stamp?

bd

Chuck(G)
May 29th, 2009, 09:19 AM
Question

If you look at this picture, and the tube silkscreens (for example)
http://vintagecomputer.net/donner/donner_3500_amplifier-front-1.JPG

Is there a way by looking at the tubes or other components from the late 50's early 60's to id the date the components were made, similar to the later TTL chips have a date stamp?

bd

Very cool, Bill! Is the "Donner" the same as in "Systron Donner"?

Many of the tubes have lot numbers on them, but it's pretty likely that any information as to production dates is likely lost. Have you checked the chassis for stamps or maintenance labels? I've got an old BuShips receiver that I was delighted to find the maintenance log penciled in under an access cover. (It was last serviced in Okinawa in 1945).

billdeg
May 29th, 2009, 10:32 AM
Very cool, Bill! Is the "Donner" the same as in "Systron Donner"?

Many of the tubes have lot numbers on them, but it's pretty likely that any information as to production dates is likely lost. Have you checked the chassis for stamps or maintenance labels? I've got an old BuShips receiver that I was delighted to find the maintenance log penciled in under an access cover. (It was last serviced in Okinawa in 1945).

Yes Donner became Systron Donner in early 1960. I have not checked for service stamps, etc. I still need to take apart, clean the computer, test continuity, etc. as well.

Bill

tezza
May 29th, 2009, 12:47 PM
Cool machine Bill,

What would these early transportables be used for. Anyone know?

Tez

billdeg
May 29th, 2009, 01:00 PM
According to the soon-to-be-uploaded Instruction Manual, all kinds of field and classroom uses. There is a section of the manual with a list of applications. When I post this I will let you all know.
bd

tezza
May 29th, 2009, 01:04 PM
It certainly must be something to have these REALLY OLD vintage computers. valves. Wow. I'm assuming parts would be near impossible to come by.

Anyway good luck with getting it going Bill.

Tez

Dwight Elvey
May 30th, 2009, 06:45 AM
According to the soon-to-be-uploaded Instruction Manual, all kinds of field and classroom uses. There is a section of the manual with a list of applications. When I post this I will let you all know.
bd

Hi Bill
The biggest issue with these old machines is the electrolytics. They
should be reformed. You'll need to make up a number of patches.
to check the opamps. It isn't too hard, you just wire them as 1:1
inverters and use the meter and a set point pot to ensure that they
track.
After looking at your pictures I'm sure the patch board I have is
not the same model.
Dwight

Dwight Elvey
May 30th, 2009, 07:18 AM
Question

If you look at this picture, and the tube silkscreens (for example)
http://vintagecomputer.net/donner/donner_3500_amplifier-front-1.JPG

Is there a way by looking at the tubes or other components from the late 50's early 60's to id the date the components were made, similar to the later TTL chips have a date stamp?

bd

Hi Bill
I noticed it has some of those metal encased capacitors.
These often have date codes.
The tubes often have date codes as well.
Dwight

billdeg
June 2nd, 2009, 11:13 AM
I should have something to report in a week and a half.
bd

billdeg
June 15th, 2009, 05:38 AM
Tubes - all tested OK. That's encouraging, but the electronic connections, capacitors, etc are more likely to have faults due to age.
http://vintagecomputer.net/donner/thm_donner_3500_6-tube-card-front.JPG

altec1
September 3rd, 2010, 02:21 PM
I have one too S/N # 124

billdeg
September 3rd, 2010, 05:59 PM
There is one for sale on Ebay now too

Dwight Elvey
September 4th, 2010, 08:37 AM
Hi
If interested, I can show the patching I do to make
a spiraljyra like plot.
I just combine two oscillators, one fast and one slow.
Changing parameters, one can do a number of intersting
things, like ovals on top of spheres.
It uses two integrators for each oscillator. There is a trick
I do the keep it from dampening out because of
lost phase shift.
Dwight

altec1
September 4th, 2010, 02:09 PM
I didn't see it on Ebay. I was thinking of selling mine. It would need a good cleaning. Any ideas of what it would be worth in it's present state and if I restored it. thanks Keith in Victoria

Dwight Elvey
September 4th, 2010, 08:36 PM
Hi
Try the number 190436568866. Right now, it has one bid at
$500. I expect it to go higher but you never know which way the wind
blows.
I'd wait at least 3 months before putting another one up unless
you think the third highest bid is fine.
Dwight

Dwight Elvey
September 4th, 2010, 08:40 PM
Hi
If interested, I can show the patching I do to make
a spiraljyra like plot.
I just combine two oscillators, one fast and one slow.
Changing parameters, one can do a number of intersting
things, like ovals on top of spheres.
It uses two integrators for each oscillator. There is a trick
I do the keep it from dampening out because of
lost phase shift.
Dwight

Hi
Actually it takes 3 amps, two of them being inergrators
for each oscillator. Actually, the slow speed one doesn't
have a problem since it make only one revolution. It is
the high speed one that looses a little bit on each
cycle.
Dwight

billdeg
September 4th, 2010, 08:59 PM
I am interested.

altec1
September 4th, 2010, 10:26 PM
Looks like I found some more parts to this beast! I think I will probably sell the unit as this doesn't really fit into my mancave. I restore test equipment from the 50's and 60's

Ole Juul
September 4th, 2010, 10:48 PM
. . . thanks Keith in Victoria

Did you say Victoria? Have a look at this thread (http://www.vintage-computer.com/vcforum/showthread.php?21636-UVic-selling-Vintage-Terminals). We have a job for you. hehe

Dwight Elvey
September 5th, 2010, 06:09 AM
Hi
I see patch cables, resistor blocks and some capacitor.
These are always a sure thing to increase value.
Dwight

Dwight Elvey
September 5th, 2010, 06:41 AM
Hi Bill
If you put two intergrators in a series loop, you'll find that over time,
they will dampen out. I've seen various explanations for this on the
web. One says that careful balancing is need while another says that
it needs more gain.
I tried fiddling with the balance and it mad no difference. The half time
was about the same. Then I tried input gain. It made a nice elipse
instead of a circle that would dampen out.
I then realized that both were wrong. It was phase error. We like
to think of intergrators as exactly 90 degrees but that isn't
true. The actual gain of the amplifier, not being infinity, means
that there will always be a small phase loss on each cycle.
It is like snipping a little off each cycle.
I found that adding one highly divided down inverter across
one of the intergrators was enough to compensate for the
lost energy on each cycle. On mine, unit, it uses transistor
opamps. These have a gain between 1000 and 10,000
someplace. I attenuate the signal with a large series resistor
and a gain pot attenuator until I just balance the loss.
Because I run a really long cycle for the main circle, I want
to make sure the faster cicle ( running about 50:1 ) will
not significantly dampen on one full loop around the large
slow circle. I use my Nicolet scope ( digital ) with a really
stretched out display to look for either increasing or descreasing.
Another way to deal with it, that works well with tube
opamps, is to use a diode in the feedback loop. This
works because of the nice high voltage swings.
First get a slighly increasing oscillation by the method
above. Then put two diodes in reverse parallel onto
a tap of the feedback used of the strait opamp.
In this case, it is recommended to put that attenuation
on the output of the straight opamp because you
want to get enough voltage to turn on the diodes.
If this doesn't make sense, I'll try to put together
a pdf.
Dwight

altec1
September 5th, 2010, 09:41 AM
I see the Uvic has relisted the units. I'm about 1/2 hr away. I have a Mazda Protoege hatchback that could haul that. Is there anything that you want. Shipping is expensive! I have just hauled 10 loads of old equipment already and the wife is calling me a hoarder! I have enough equipment to keep me busy for 2 years.If Uvic wants to sell it cheap and you want to buy some I might be able to buy it if the wife will let me.

altec1
September 6th, 2010, 04:40 PM
Well I see the 3500 went for 510. I might put mine on for a" buy it now "price of 400 with the extra parts or is that too much.. Anyone here interested?

billdeg
September 6th, 2010, 06:12 PM
Hi
I see patch cables, resistor blocks and some capacitor.
These are always a sure thing to increase value.
Dwight

I don't have to make connectors and blocks/capacitors. These I would like to find for sure.

I can't believe this sold so cheap, I would think that a Donner 3500 would sell for more than a similar condition Altair, but I guess that's not the case.

fengland
October 14th, 2010, 05:38 AM
That's definitely one of the coolest things I've seen - haven't seen a commercial analog computer before.

EvanK
October 18th, 2010, 08:36 PM
I would think that a Donner 3500 would sell for more than a similar condition Altair

Nah. 3500 is obscure. Few people ever heard of it or understand what it is.