[Elecraft] KPA500 receive loss

[Dr. William J. Schmidt]

I'm sure you could invent many ways to protect these parts (gas tubes, sacrificial TVS diodes, fusing, etc.).  The best way, of course, is to disconnect it (which of course I did not do).  These are low voltage parts on the receive side path so I don't know if a gas tube would be appropriate here...  Someone with more experience with them can chime in here.


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ 

email:  bill at wjschmidt.com


-----Original Message-----
From: CUTTER DAVID <d.cutter at ntlworld.com> 
Sent: Saturday, June 5, 2021 10:46 AM
To: bill at wjschmidt.com; Elecraft Mail List <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] KPA500 receive loss

Would a gas discharge tube save the sensitive parts?

David G3UNA


> On 05 June 2021 at 16:20 "Dr. William J. Schmidt" <bill at wjschmidt.com> wrote:
> 
> 
> This happened with my backup amp at the contest station on J6.  I left 
> it connected by accident overnight (too much rum) and we had some 
> static storms.  Took out the pin diodes (well, more accurately the 
> diodes that act like PIN diodes).  When put in operate, the receive 
> drops by 30+ dB but still transmits fine.  A simple replacement of the 
> four diodes and three (?) transistors solved the problem.  Dirt cheap.  
> You can make these measurements at the test-points to confirm:
> 
> 
> TP2= RX 13.1, TX 0.8
> TP4= RX 3.9, TX 13
> 
> 
> Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ 
> PJ2/K9HZ
> 
> email:  bill at wjschmidt.com
>


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