The term Crowbar applies to any protection circuit that shuts down a power supply very quickly, as if you placed a Crowbar across the terminals and shorted it out. The metaphor of a crowbar is used because it is made of thick metal that will not melt and can handle a great deal of current. Hope that helps, Russ
Thanks! We just had to change a Thyratron In our old converted-from-analog Sigma transmitter. This video is nicely done and explains crowbar testing very well! Mike
2:39 I'm surprised they don't put a fuse in series between the capacitor and the thyratron. Seems like that would reduce the demand on the thyratron, since it wouldn't have to drain the whole charge on the capacitor to trip the input circuit breaker. The fuse would blow before the capacitor was fully discharged.
Yeesh! Some of these photos show an unacceptably dirty high voltage compartment. Dust is the enemy. This area must be hospital clean. In fact we replaced the input air filters with HEPA grade filters. If you ever see a compartment this dirty, turn the high voltage off, discharge everything with the grounding stick and verify safe, then go get a bunch of lint-free rags and a gallon of denatured alcohol, and get to work. Old t-shirts work well. Clean EVERYTHING including the red and white wires. This will result in less corona and far fewer high voltage trips and crowbar events. Even the skin oils from your fingers are bad. Use alcohol to wipe everything down that you have touched.
The term Crowbar applies to any protection circuit that shuts down a power supply very quickly, as if you placed a Crowbar across the terminals and shorted it out. The metaphor of a crowbar is used because it is made of thick metal that will not melt and can handle a great deal of current. Hope that helps, Russ
Thank you for the fascinating video. The excellent animations and graphs are very helpful additions to the photos of the equipment.
Oops.
I used an actual crowbar.
Thanks! We just had to change a Thyratron In our old converted-from-analog Sigma transmitter. This video is nicely done and explains crowbar testing very well!
Mike
2:39 I'm surprised they don't put a fuse in series between the capacitor and the thyratron. Seems like that would reduce the demand on the thyratron, since it wouldn't have to drain the whole charge on the capacitor to trip the input circuit breaker. The fuse would blow before the capacitor was fully discharged.
I wish I had these videos back in the early 1990s when I used to work on this equipment. It is a surprise I'm still alive. ⚡⚡⚡
how much does one of those crowbar testers go for? I found one in my family members storage.
But, as often happens the $35,000 IOT will sacrifice to save the crowbar circuit.
MOSFETs are putting an end to this.
Unfortunately he will never see this message. My apologies
Why is it called the crowbar, anyway?
You forgot to include the most important part of the video- footage of the friggin test! 😫
Excuse my ignorance, but what is an IOT?
Vacuum Tube. Similar to the Magnetron tube in our microwave ovens, except more $$$$$$$$
When working on kit like this, the S.I.D.E. rule is implimented.....switch off, isolate, dump, earth, thats what we were taught.
Yeesh! Some of these photos show an unacceptably dirty high voltage compartment. Dust is the enemy. This area must be hospital clean. In fact we replaced the input air filters with HEPA grade filters. If you ever see a compartment this dirty, turn the high voltage off, discharge everything with the grounding stick and verify safe, then go get a bunch of lint-free rags and a gallon of denatured alcohol, and get to work. Old t-shirts work well. Clean EVERYTHING including the red and white wires. This will result in less corona and far fewer high voltage trips and crowbar events. Even the skin oils from your fingers are bad. Use alcohol to wipe everything down that you have touched.