On 22 Apr 2009 at 21:17, Yokshs wrote:

Hi all,

Well, I finally did it. I let the smoke out of my Icom AG-35 preamp!

I've read several such messages on the list over the years. Glad to know I'm not alone in this club.. hi hi

Before I replace the 3SK121 with an identical unit, I wonder if anyone has used a similar FET with better NF? The AG-35 specs I found stated 1.5 dB NF and 15 dB gain.

I went through my collection of new parts and found a few Agilent ATF 54143 hemt..

The NF on similar designs is more like .38 to .5 dB and gain is 19-22 dB.

I wonder if anyone else has had the wild idea of rebuilding their preamp? I'd like to retain the enclosure and relays, etc.

Several 54143 designs are available, such as this one:

http://www.qsl.net/yu1aw/atf54143eng.htm

Thanks for any help or ideas.

73,

Kyle K0KN

I fried my UHF one too...I order a couple from ICOM. With my very limited electronics building skills i cut the dead one leaving as much legs as possible and i resolder the replacement over the cut legs. Not elegant but quick and effective. Is this is achieving the same overall previous gain figures? that i don't know but it works.

I have another one to replace in a different type of preamp but the FET is below a lot of other components and he's flat mounted (No legs) i don't come up with a solution with this one?

"-"

Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE