/usr/local

Tuesday, January 20, 2015

Name that ware

It is a HP 202A Low Frequency Function Generator, which was introduced in 1952, the model here is the slightly revamped one from 1959 onwards (I cannot find an exact production date on it, so I guesstimate it in the early 1960s). It can generate sine, triangular and square waves from 0.01Hz up to ~1200Hz and is still working properly after ~50 years. I guess the unit has been maintained and serviced over the years, so the tubes must be all quite newer than the unit itself.

The sine wave is "synthesized" from the triangular wave using a network of silicon diodes and resistors with about 1%rms distortion, more about that in the manual: http://www.hparchive.com/Manuals/HP-202A-Manual-SNprefix-037.pdf

A company where I interned as a student phased them out and they landed in a dumpster where I rescued one and another complete set of tubes from another one. It is missing it's top cover and enclosure, I guess it was sitting inside a 19" rack for most of its active time. Since then it has been sitting in my parents basements for another 20 years

https://plus.google.com/u/0/+VladimirPantelic/posts/BrArMh9wmeG

look Ma, I made a ... mess

buffer/5 band EQ/booster and headphone amp with aux line-in mix

https://plus.google.com/u/0/+VladimirPantelic/posts/DxDJwM945HT

the SMINT amp

because using Altoids tins is so 2012

https://plus.google.com/u/0/+VladimirPantelic/posts/TehojP9GEeJ

Monday, January 19, 2015

Drain Cam v2

Made from a 50mm water pipe bushing and two end caps. LEDs powered by 2 AA batteries and a Reed switch. One length of pipe was cut open lengthwise to form a sleeve around the bushing, inset is a small ball magnet that activates the Reed switch when the sleeve is rotated into the right position. Attached at the back is a spiral drain cleaner which allows to push the camera down the pipe and rotate it if needed.

I had to 3D print the battery holders as ordinary ones were too large and interfered with the camera body in the middle of the pipe.

I made the mistake of using polypropylene (PP) pipe which is almost impossible to glue, e.g. epoxy and superglue don't really stick to it, so it proved really hard to seal the thing. I ended up filling both end caps completely with silicon caulk just to be on the safe side.

https://plus.google.com/u/0/+VladimirPantelic/posts/bZk3xoJLs7A