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Dead bug is not dead - yet

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PekkaNF:
Dead bug construction that is.

Needed something to check short 50 ohm coax cables/terminations.

Found this TDR article and build it semi dead bug style. Stripped out all the extras I did not need: One capacitor, no extra provisions for other output impedance than 50 ohm.

 I had a bit too small capacitor, it oscilated funny ---think 65 MHz and sort of sine, but not that sure - scope is 50 MHz and pretty sure signal folded. Soldered next size up and then is works.

I think it needs a metal box.

Also I'm considering a different circuit, the pulse could be shorter and sharper.
http://support.fccps.cz/download/adv/frr/Reflectoprobe/reflectoprobe.html

Last picture with one metre of coax, T-connector and 50 ohm terminator. Needs a bit more work.

Pekka

PekkaNF:
I know that my scope is a bit slow for this one, but have to try and see if I can produce a pulse that will yield to response I can use.

Rubes:
back in the day as an engineering tech...the engineer gave me a schematic and said build this...make the leads as short as possible.
There wern't many parts, so I gave up  the perfboard and just started soldering component leads together. It ended up being a pile of parts a little bigger than a golfball. he  :bugeye: :wack: and said how am I supposed to troubleshoot that??? I said you wont have too...worked like a champ...he dubbed them 3d circuits.

PekkaNF:
Once Pretty badly documented Siemens PLC would not start. Power went on and measured the correct voltages on rack backplane. PLC just would not start. In France. In a pretty hard spot. And really bad timing, mill would go down fast. The whole works.

Yanked the PSU out and found a dead bug in the SMPSU "power good" circuit. Took my toothbrush and some IPA to clean the fried bugger out.

There was still asort of cocroach print on the PCB when I gingerelly put the PSU back and poewered the thing up. All the right leds started blinking and the PLC sprung back to life and my bacon was saved. I really should have paid better to save the day, but I was young and it was a compliment if I didn't got biched up couple times a day.

eskoilola:
The usual reward of a job well done - is to be able to continue doing that good job.

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