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January 7th 06, 09:23 PM posted to rec.radio.shortwave

In article
,
Telamon wrote:

In article .com,
wrote:

Stereo amps run fine without a load. I suppose there could be a poorly
engineered stereo with gain in the output stage that would be unstable
without a load, but that wouldn't cause it to blow up.

There are a few electronic items that can be blown if not loaded. Some
RF amplifiers can't handle the no-load condition, but most modern gear
is engineered to handle no load and shorts. Some poorly engineered
Dc/Dc converters can't handle the no-load condition.

Snip

That's because an load open just like a short load causes the RF
amplifier output to dissipate two times the output power. Opens and
shorts both cause 100% power reflections. On older generation equipment
operating into an open or short usually meant the output would be blown.
Equipment built these days have more power handling margin on the small
signal stuff. Usually the higher you go in frequency capability the less
likely an amplifier will withstand a 100% reflection. Big amplifiers
will still get destroyed at any frequency. High power TWT's can be
ruined in a few seconds. The prior comments refer to utility amplifiers.
Commercial ham gear these days have power fold-back protection that
usually but not always saves the finals.

I see you also referred to DC to DC converters. Those devices along with
many industrial power supplies have minimum load requirements for the
control feedback circuits to operate within specifications. Without the
minimum loads the gain/phase of the control circuitry can go into a
positive feedback mode when they are supposed to be in a negative
feedback mode so yeah they can even blow up for that reason, which is a
completely different reason from the RF amplifiers explanation.

--
Telamon
Ventura, California