
Understanding and repairing the power supply from a 1969 analog computer - robin_reala
http://www.righto.com/2019/11/understanding-and-repairing-power.html
======
blendo
What's the "Hello, World!" for an analog computer? Can you build it on a
breadboard?

Asking while enrolled Electronics 102 at my local community college (diode and
transistor circuits, not yet op-amps.)

~~~
pkaye
You can use op-amps to build circuits that add/subtract voltages, scale by a
constant, integrate, differentiate. You can combine these to model
differential equations. And yes, you can build the equivalent circuits on a
breadboard.

Here is a book to learn a little about them:
[http://www.analogmuseum.org/library/handbook_of_analog_compu...](http://www.analogmuseum.org/library/handbook_of_analog_computation.pdf)

~~~
Animats
Yes. Analog op-amp ICs are cheap, fun to play with on a breadboard, and
amazingly accurate.

Some op-amp projects: [1] A 741 op-amp in DIP packaging is $0.56 on Digi-Key.

[1] [https://bestengineeringprojects.com/operation-
amplifier-741-...](https://bestengineeringprojects.com/operation-
amplifier-741-based-projects/)

~~~
segfaultbuserr
For a more modern chip, use TL071/TL081 general-purpose JFET opamp, costs
$0.55-$0.61 in DIP.

~~~
Junk_Collector
I actually think that novice hobbyists are better off with the venerable 741
because there is just so much clear and concise documentation on it's use in
hobby projects that have accumulated over the years. Once you have a grasp of
what the different specifications mean, then it's easy to make the jump to
other more modern chips with better performance.

~~~
Animats
Yes. The 741 data sheet says "The amplifiers offer many features which make
their application nearly foolproof: overload protection on the input and
output, no latch-up when the common-mode range is exceeded,as well as freedom
from oscillations." The newer TL07/TL08 series has 3x the bandwidth (to 3MHz)
and can be trimmed to higher precision, but comes with more PC board layout
restrictions on the data sheet. For solderless breadboard use, the lower-
bandwidth part may be easier to deal with.

(I haven't played with op-amps in years. Back in the 1990s, I tried to build a
LIDAR, but I needed more expensive RF-type test gear than I could afford.)

~~~
segfaultbuserr
When you can get a 100 MHz opamp for $15 today, 3 MHz is low bandwidth. But I
agree, anything faster than TL07/TL08 would be problematic on a breadboard.

On the other hand, a small double-layer circuit board can be as low as $5
nowadays.

