The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Can the Irf510 mosfet from radio shack ($1.99) be used in place of a 2sc1969 or 2sc2078 final? Does it need the companion part like a IRF520 or ERF2030 does and what should the voltage at the gate be?

I was thinking of trying this on a cobra 29 ltd with the 2sc2078 or a Galaxy DX959 that has the 2sc1969.

Galaxy now uses the IRF-520, and there are several changes to be made when using one that originally used a 1969. The directions are on the web in several places....

The 510 is a 5~15 watt fet. It makes a better driver than final though. The problem is Rds - the on Resistance, which is 0.4 ohms for the IRF510. The output impedance seen by the FET is roughly V*V/2P where V is DC supply voltage and P = power out.
If P = 10 and V=12 then the output impedance is about 12*12/2*10 = 7.2 Ohms.
As the value of Rds gets larger relative to the output impedance the efficciency drops and you start producing more heat and less RF.

For the 29, use the erf 2030, it is alot simpler and will provide the same result. be sure to remove the tuning slug from L14 and not remove the entire tuning coil. (some old directions out there on the web say to remove it completely) If the audio diode is clipped, put it back to stock and adjust VR4 for CLEAN, proper audio. They sound better if you don't use a swing kit with the EKL mod. They tend to just distort and bleed over more.

Thanks for the reply redeye. Is the IRF520 the same as the ERF2030? I've read in some forums that it was. Do you know if it is?

The EKL is a proprietary device, meaning EKL is the only producer. My honest guess is that is is very similar to the 520 or the 510, but as all good proprietary devices sometimes do, they may have a different value somewhere inside making it "different" from another make. I really don't know though....