[amsat-bb] Mirage KP-2 2 meter preamp help

[w4upd]

There are town versions of this preamp. The first and older version is 
mounted in a cast aluminum box which provides rf shielding. The newer 
version is mounted in a plastic box with stainless steel angle bracket. 
Each are slightly different in the components.

Reid, W4UPD


On 2/15/2016 7:17 PM, Larry Ryan wrote:
> I am trying to repair a Mirage KP-2 series mast-mount 2M preamp. It is
> quite old. Also, I have the companion bias-tee or Control Box as Mirage
> calls it. Also, I have the 70CM Mirage preamp which works really well.
>
> I have contacted MFJ for info and they are very agreeable and they "need to
> check one part numbers, etc." but never return a call. When I call them
> back, I get the same very polite and agreeable "need to check....".  I have
> done this 3 times without getting any info from them.
>
> The problem is not in the Control Box - they both work well with the
> working KP-2 70CM preamp.
>
> Have any of you repaired a KP-2 2M preamp?
>
> Do any of you have a schematic diagram of this preamp?
>
> Do any of you know the part number of the gasfet transistor? (I'm thinking
> its the problem)
>
> Details:  I have cleaned up and tested the preamp. It seems that the
> internal bias-tee relay is working properly and there are voltages on the
> transistors that seem to match the working KP-2 70CM preamp. The preamps
> were mounted on my M2 circularly polarized arrays at a previous QTH.
> Presently, I'm setting up two much smaller antennas and I want to use these
> preamps. I'm reasonably sure its the gasfet transistor. I Googled this
> topic extensively and I find other hams asking this same question without
> an answer in postings from 2001 to 2012. No schematic and no part number
> for the gasfet. At $200 each, I want to try to repair it.
>
> Any help would be appreciated.
>
> Thanks & 73, Larry W7DGP
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