[BC] In search of Harris SX1

[dynotherm at earthlink.net]

Chuck,

Basically you are correct. Harris has always recommended pair replacement,
but working with 5's I have found this results in pulling a lot of good
transistors in boxes with low dissipation. The theory is that if you
blow one transistor all four in the quad should be changed as a precaution.

If the other problems - matching, overmodulation etc. - are solved when
the dissipation is nicely in the safe range AND installation is correct,
the failure rate goes down.

Phil Alexander, CSRE, AMD

-----Original Message-----
>From: cldube <cld at admin.umass.edu>
>
>My experience with the SX series is not if you'll need to replace 
>transistors, but when.
>I made replacements- about 2 per year and usually after severe weather on 
>these transmitters, even when new
>and very well matched to the antenna system. The transistors should be 
>replaced in matched pairs for best results.
>And these parts are no longer available from Harris nor anyone else that I 
>know of. So essentially you'll be buying a box that will eventually be 
>running at reduced power and eventually, no power out.