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 _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb