mosfet on a 29 ltd

[zebbman]

ok. 1 down now on to the next. bought a irf 520 kit on ebay. want to put it in my old 29 ltd which has a blown final. came with instructions but to say the least they leave alot to be desired.

MOSFET Supertune (29LTD classic and newer): Replace stock final with IRF520 MOSFET transistor (pin-for-pin match when installing). Remove R56 and in its place install a 470-ohm resistor in series with a common switching diode (1n914 or similar), with the banded end of the diode towards the front of the radio. Remove C53 and solder it across C59. In C53's place solder a 3.3k resistor. Remove C 61 and solder it across C62. Remove C126. Remove R55 amd solder a 22pf cap in its place. Remove the slug from L14. Replace C71 with a 33-47uf cap. Turn VR4 (AMC) counterclockwise fully. Gently spread L13 and L12 and tweak the spreads for best PEP when modulated. Tweak L20 and L17 for best PEP when modulated. After tuning is finished, set VR4 to half-way.

Note: Older 29's (LTD and GTL) use the same basic procedure, but instead of re-using the caps, place a 100pf across C62, a 68pf across C59, and 22pf across the spot where you removed R55.

i only see one hole for r56. the other hole says L23 maybe..hard to see. is that where the other end of the diode goes? ive also seen the same mod with many less parts changed out. ive also seen some that say not to remove the L14 slug. i have the parts and a soldering iron and im ready to go. let me know if you can simplify this as im a simple man...pics would be very helpful also. help me out here, im on a role

 

[Carl]

does this help any?

http://cbtricks.com/miscellaneous/fet_papers/ekl/graphics/erf2030_cobra_29_mod.jpg

 

[zebbman]

what is L26 by r56. r56 is the resistor with the black ferrite looking thing on it

 

[AudioShockwav]

r56 is the resistor with the black ferrite looking thing on it

Here are some pictures of Resistors

R56 looks like one of them and L26 is the wire with a bead......
A wire with a bead slipped over it is a type of inductor.


73
Jeff

 

[zebbman]

looks like the resistor is inline with that bead

 

[zebbman]

i looked again and that bead is on r56

 

[zebbman]

ok. i pulled r56. i guess thats just a ferrite on the r56. mod is complete except for the resistor and diode part. i soldered the 2 together as instructions say. my only question is which way should i put it in. says its polarized and the banded part of the diode should face front of the radio. no problem there but which way should i put it in. there is a circle with a line on the board. does it matter which hole the resistor goes in as long as the band faces forward. wish i just had the 1230 chip. does radioshack have these or something similar?

 

[zebbman]

took awhile but its complete. for someone with my expertise (or should i say lack of) it wasnt as difficult as i made myself believe. i did everything by the book and my hands were actually shaking as i turned on the power supply while at the ready to turn it off just as quick at the first sign of smoke. to my surprise not a single puff. i actually had receive. i heard a friend but until now he could never hear me. i gave him a shout and once again to my surprise he heard me. he is actually my cb tech whom i have paid alot of money over the years to do this kind of work for me. of course he doubted i could actually do it but thats only because i was taking money out of his pocket. i had my doubts but it must have worked or he would never had heard me. im the local mud duck on a dipole antenna in my attic. i havent tuned the radio as i dont have the equiptment so he will still get a few of my dollars. i am anxious to see what its doing on his meters. thanks for the assistance and i will return here with question on my next project.