so_lo_saturn wrote:I did the schottky diode mod to my uniden. It worked then I did the ef2030 mod and I went step by step from cb tricks directions. Now when I key the mic all I get is static. So I bought a general hp40w. Could the preamp transistor be bad?
Good morning so_lo_saturn
I apologize for having to post my opinion here I lost my draft in the original forum.
I recommend restoring the radio back to the bi-polar 2SC-2078. There is no advantage to using a MOSFET as a Final. It was done to make the radio cheaper not better. Bi-polar Transistors are resilient and can survive a higher SWR before popping. In fact the Uniden 76 or Cobra 29 LTD made in Taiwan or the Philippines can be keyed up without an antenna for 5 minutes or more and not fail. The Mosfet would be toast is less than a minute.
The Bi-polar 2SC-2078 can survive up to a minute into a direct short at the antenna jack. A Mosfet will not.
In my humble opinion you should get rid of the Schottly Diode. It is not worth the other issues you will create. The output of the Final is connected via a 10 pfd to 15 pfd capacitor to the first preamp transistor 2SC-1674. If the Mosfet failed and is shorted it could damage the the 1st RF transistor 2SC-1674. I have come across this on average about once a year. Chances are your 2SC-1674 is fine, but if the Final has a short it can load down the 1st RF transistor. If the Final is oscillating on receive it would get to the 1st RF transistor.
I recommend a better method for a preamp that someone posted the other day. I wish I could find his post as well that went along with this link. He tried it and says it is superior to the Schottly diode mod. He also is a Ham operator. I want to give credit where credit is due. I will provide the link here:
http://www.amwindow.org/tech/ ... disdet.htm
Respectfully