That sounds odd to me. True PIN diodes are current actuated devices.
The carrier lifetimes are long enough that the devices are "on" even if
the signal peaks exceed the voltage of the control current ... as long,
of course, as the control current exceeds the signal current.
On the other hand, I've heard that Elecraft has sometimes used regular
switching diodes instead of PINs, and for those you need a voltage that
exceeds the peak voltage of whatever you're switching.
Both types of diodes have their place ... using one where the other
works better is not good practice.
73,
Dave AB7E
On 8/26/2021 11:33 AM, Fred Jensen wrote:
I think the 270 V circuit is DC bias for the PIN diodes in the TR-switch.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
On 8/26/2021 10:32 AM, Chuck Chandler wrote:
My KPA-500 has been running great for several years. Recently I
noticed it
was making the occasional extra "click" or "thunk" upon powering up or
down. Usually it would "click" when powered up and again when powered
down, but recently a few seconds after the first click there would be
another one, maybe more of a thunk sound.
This afternoon I turned it on and when I pushed the Operate/Standby
button
I got a fault light and the 270V ERR message on the display. The menu HV
option shows 68.4V, varying a bit, on my 240V line. I put it on the
bench
and opened up the top cover. There is a smell of overheated components,
maybe burnt but more like too hot.
I've submitted the contact form on the Elecraft support page. Any
suggestions? For now, I'm running barefoot...
73 de Chuck, WS1L
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