EAI TR-20 Analog Computer

[cbowen]

I managed to pick up an EAI TR-20 Analog Computer on eBay and have been working on restoring it. I created a blog at http://eai-tr20.blogspot.com/ in case anyone is interested. It's been surprisingly painless so far getting it working, considering it is about 45 years old.

 

[dave_m]

Your work to date is very impressive. Just wait until you solve your first differential equation on the machine. What fun!

 

[g4ugm]

Very nice, been looking for one myself for ages with no luck so wonder when you actually bought it.

In fact so little luck I have started building a simple one myself, but no blog yet....

 

[g4ugm]

Mind you I musn't complain too much. I do get to use the Hartree Differential Analyser at MOSI Manchester:-

http://www.mosi.org.uk/explore-mosi...nce-technology/calculating-and-computing.aspx

(big green thing at the top of the page) sadly we only have one integrator working at present so we can only solve very simple differential equations.....

Dave

 

[cbowen]

Very nice, been looking for one myself for ages with no luck so wonder when you actually bought it.

I picked it up in early April. I've had an eBay watch forever just about, but could not really afford the prices I was seeing. A TR-10, which is nowhere near as capable a machine and was missing the patch panel, went for well over $1000 a while back. When this came up I put in a snipe at a price I could afford and was shocked to get it.

An advantage was that it's a heavy item. It weights about 100 pounds (they really built this thing). So, the seller wanted local pickup or a lot of money to ship. We had to drive about 5 hours to pick it up. It was filthy when I got it, but it's cleaning up very well. And, so far I've had very little electronic trouble. I was careful bringing it back up and had to replace the transistors in the reference power supply. There's one amplifier that is a bit wonky right now as well, but other than that it's working quite well.

 

[inotarobot]

Hi there,

do you still own your TR-20 ?

And have you got it fully functional ?

 

[g4ugm]

I now own a TR-10 which is actually just as functional as the TR20. Its not 100% working but there are enough to do some interesting things/ Check out my blog on this site.

 

[dluck]

Nice work. I'm working on my TR-20 now. The power supply came up. The +15V, -15V, and 30V are nice and steady, no measurable ripple. But the +-10V reference supply does not. I'm using my cap-wizard to help find bad caps. So far found 3. Is there really any difference between the TR-10 and the TR-20? How did you make your extender cable? I'm thinking I need to make one myself. Did you figure out a way to restore the lettering? It seems to me there are stencil kits available to put new lettering on. When you replaced the power transistors on the reference board had you determined they were bad?

 

[Dwight Elvey]

Hi Dale
I don't know if cbowen is watching the MB every day. He did a post on April 11 of this year so I expect he may be checking in. Of course he may be waiting to figure what to do about the new message board.
I'd like to know what he did to get such a nice circle, without doing some phase compensation. There is always a small loss from the gain of the integrators. When they integrate, there is always a small error in the 90 degrees. This accumulates. I think it can be compensated by offset adjustments but it takes both integrators to have an offset. This looks like a DC offset but it is really caused by the slight gain loss. Dave is in the UK so it may take a day or so for him to respond.
Stay Safe
Dwight

 

[jd2147]

I actually worked at EAI in 1984 and my father retired from there in 1991 after about 25 years.