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Old 4th June 2013, 01:32 PM   #1
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Default Construction tips for high voltage amps.

There is a safety sticky for high voltage. I'm interested in construction tips for high voltage amps. Since I'm planning a 1000V B+ amp.
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Old 4th June 2013, 02:01 PM   #2
DF96 is offline DF96  England
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Have a look at the techniques used by radio amateurs for their high power RF amps and PSUs, as they often use quite high voltage too. Sometimes known as 'linears', and typically using tetrodes operating in Class B.
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Old 4th June 2013, 02:38 PM   #3
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Quote:
Have a look at the techniques used by radio amateurs for their high power RF amps and PSUs
I don't think I've ever seen a good site detailing the build of a high powered RF amp. Got a link perhaps?
Thanks.
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Old 4th June 2013, 02:44 PM   #4
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Possibly you can find a (used) copy of The ARRL Handbook. All sorts of useful info.
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Old 4th June 2013, 04:04 PM   #5
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Generally I would say that if you use wire with a rated voltage with some head room, there is no special precations, except at where the wire is mounted, you will need bigger distances and isolation.

1kV double isolated wire is common and can be found from anyone building or supplying for electrical control panel construction.

1kV is still low enough to be of little concern in my opponion regarding coupling between wires, at 4kV I have noticed capacative coupling between wires affecting performance.

Give a good 10 mm distance to anything and you are on your way. Avoid materials near that contains carbon as high voltage easily can creep/burn along a carbon track, even over long distances.

If you really want to be sure, keep all surfaces conducting the high voltage round, sharp edges are known as break out point and at higher voltages can result in corona losses. Epoxy or varnish everything soldered for higher isolation.

You could also incapsulate the wires in clear tubing, fill it with oil, but this is way over the top for a mere 1kV.

A good and cheap source for high voltage wire, old TV sets, there you can salvage some 50 cm per set of 10-15kV rated wire.

I hope these experiences from a high voltage amateur can be of help
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Old 4th June 2013, 04:34 PM   #6
DF96 is offline DF96  England
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Quote:
I don't think I've ever seen a good site detailing the build of a high powered RF amp. Got a link perhaps?
Sorry, most of the stuff is still on paper. Best to look on ebay for 1960s ARRL or RSGB handbooks.
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Old 4th June 2013, 05:38 PM   #7
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Originally Posted by DF96 View Post
Sorry, most of the stuff is still on paper. Best to look on ebay for 1960s ARRL or RSGB handbooks.
There is around a hundred titles online here, old scanned radio books, should be just what you are looking for.

Technical books online
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Old 4th June 2013, 05:57 PM   #8
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Hi Bas,

I always use double insulation for such high voltages. I pull an extra sleeve over the wire. Make sure no high voltage carrying wire gets clamped anywhere in the chassis or nicked or insulation accidentally burned with the soldering iron.

For 1kV keep 1cm distance between bare metal. Note that the plate of the output tube can swing up to twice the B+. So extra care is needed there. Mount the tube sockets such that enough creeping distance is ensured.

Ensure all parts have the proper voltage rating not only the caps (they should have ample headroom) but also chokes and resistors. Use several resistors in series for bleeder.

The heater winding of a rectifier tube will carry high voltage. Make sure the transformer has the proper insulation rating.

If the PSU operates without load it's output voltage can rise significantly. All caps should be rated to cover that case. A well sized bleeder will avoid a big voltage rise if the PSU is unloaded.

Best regards

Thomas
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Old 4th June 2013, 06:21 PM   #9
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Bas,

I use PTFE ( Teflon ) insulated wire for leads that carry high voltages.
Because of it's very high ( 60kV/mm ) breakdown voltage, it is very safe.

Dick
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Old 4th June 2013, 08:54 PM   #10
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Thanks for all the suggestions so far. I'll get some teflon sleeving for sure.
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