OK, my new MAX1406's came in today.
I really made a point to check out every possible cause for the previous
chip issues.
Installed the new MAX1406 and now have 122.1 V's at the junction of C77 and
R11. Also have a -22.4 V's at pin 8 of U4.
So, the new chip fixed this issue............
Now to move on to the next challenge.
Thanks to everybody for your suggestions and support.
73 Jerry N0JRN
----- Original Message -----
From: "Don Wilhelm" <
[hidden email]>
To: "n0jrn" <
[hidden email]>
Sent: Monday, December 14, 2009 6:22 AM
Subject: Re: [Elecraft] KPA100 problem
> Jerry,
>
> I will take back what I said about U4 - it is faulty.
> That negative voltage is there only to allow the RS-232 drivers to produce
> a negative level, the current draw should be minimal.
> The only thing U4 does is convert RS-232 levels to TTL levels and
> vice-versa.
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