Re: KPA500 No Power Output

David Cutter

I think 400W is nicely backed off and  conveniently coincides with our regs.

Lest we forget, there is a relationship between stress and reliability: I'm guessing that voltage is the lowest problem with low swr, then current in the absence of spikes, then temperature is the long term killer.  It's those loose joints in the antenna circuit we need to look out for. They can cause very nasty spikes which hollow state can withstand but solid state can be vulnerable.

David G3UNA

On 04 April 2020 at 20:17 Stephen Walls <swalls46@...> wrote:


you guessed it right.   That is what they are ! ! !

I was hoping for the diode that others talked about.
As I said,  mine are in a 'lil Zip-Lock bag hanging above the radios.

A reminder to 'back off' a bit, even though that was not the cause.


On Saturday, April 4, 2020, 03:13:48 PM EDT, Jeff Clarke <ku8e@...> wrote:

I pulled out the KPA500 today and there was something rattling around inside. Took off bottom and I found the tops of two RF MOSFET transistors. At least that what I think they are after Googling the marking on them. They are white discs with the marking "MSC BEO VRF2933 1432 B00005862 MALAYSIA H" The bottom of each disc is burnt.

This is probably going to be an expensive repair. Looks like they cost about $100 each just for parts. Hopefully this is the only damage.

Jeff KU8E



Join to automatically receive all group messages.