[photo="medium"]4775[/photo] .
[photo="medium"]4776[/photo] .
[photo="medium"]4777[/photo] .
I have done two Realistic TRC-427 radios with these steps, I only just came up with the idea to mosfet convert the TRC-427 a few days ago, so the mod could be refined by someone, anyone feel free to comment or suggest a revision!
Maybe I'll try more voltage at the gate to get a 4 watt carrier, also next time I may try FQP13N10!
If anybody is interested in seeing the RF Peak to Peak Voltage, let me know..
I can re-visit the scope and look at the volts/per div. then measure for max with audio before I see distortion in the positive peaks... That'd be more accurate than most all consumer level P.E.P. meters, "true peak reading" or not.
I had about 1 volt on the gate of the mosfet after these steps, if someone did more and added voltage the carrier and total output would increase (assuming)
I'm not worried about the "Max Watts", i'm just glad I have a cheap alternative to traditional transistors, and they have "headroom" over the factory part, maybe!?.
One radio I keyed up a few times w/ no antenna to see if the part would "instantly fail", nope it still works fine, as far as I can see.
Cheers!
Me and this duck pluckin' Realistic, are back out.
-LeapFrog
The little ferrite bead on R44 is L14, on one mod I reused this bead (on the hot lead of EN-1230) and on another mod I didn't use the ferrite bead, the radio without the L14 bead has more carrier, don't know if it's related, I'm not bothered enough to pull the bead out and compare results.
Remove R42, R41, C53
Place EN-1230 Companion part @ R42, w/ neg lead towards back of radio.
Place C53 on backside of C55, or just use a 390pF cap @ C55.
I changed R44 to a 4.7 Ohm from 6.8 Ohm, I did this on only one radio, not both; don't know what this did, if anything appreciable.
One radio had 2.25 watts carrier, the other 3.5 watts..
For giggles I "opened up the AMC" and whistled into the mic, let's just say this little mosfet works as a final... "swanging to 5,6,7 average dirty watts of splattering over-modulation".. Now I have the AMC adjusted lower than when it left the factory, but It is still near 100%, not splattering!
This was without realigning the entire radio, "I just peaked L12, L15, & L16".
AMC needed realignment due to change in the carrier level.
The carrier was too low without going over the inductors, and ultimately adding capacitance at C55 did the trick (Total 390pF).
R41 looks like the "static discharge resistor", I say to pull it, only because I was looking at Cobra 25/PC66 install instructions for ERF-2030 by EKL to create my mod, and they say to pull it.. so I did.
http://www.worldwidedx.com/threads/40-45-watt-erf2030-mod-for-cobra-25-uniden-66-68.33400/
http://www.cbtricks.com/miscellaneous/fet_papers/ekl/graphics/erf2030_cobra_25_mod.pdf
http://downloads.cobra.com/CB/Models/25-SERIES/25LTDschem.pdf
In that thread Moleculo suggested to replace R38 (cobra25/pc66) with 10K-15K Ohm, instead of pulling it. If I've compared the TRC-427 schematic correctly against the (cobra25/pc66), "R38 in my mod is R41, I could be wrong though, so compare the schematics if you like".
Thanks Moleculo, EKL, CBTricks, and the WWDX forum members who have discussed using the mosfet parts in the past. Cheers -LeapFrog
[photo="medium"]4776[/photo] .
[photo="medium"]4777[/photo] .
I have done two Realistic TRC-427 radios with these steps, I only just came up with the idea to mosfet convert the TRC-427 a few days ago, so the mod could be refined by someone, anyone feel free to comment or suggest a revision!
Maybe I'll try more voltage at the gate to get a 4 watt carrier, also next time I may try FQP13N10!
If anybody is interested in seeing the RF Peak to Peak Voltage, let me know..
I can re-visit the scope and look at the volts/per div. then measure for max with audio before I see distortion in the positive peaks... That'd be more accurate than most all consumer level P.E.P. meters, "true peak reading" or not.
I had about 1 volt on the gate of the mosfet after these steps, if someone did more and added voltage the carrier and total output would increase (assuming)
I'm not worried about the "Max Watts", i'm just glad I have a cheap alternative to traditional transistors, and they have "headroom" over the factory part, maybe!?.
One radio I keyed up a few times w/ no antenna to see if the part would "instantly fail", nope it still works fine, as far as I can see.
Cheers!
Me and this duck pluckin' Realistic, are back out.
-LeapFrog
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