ok.....want to do 520 mosfet in a cobra 29 but not sure which instruction to use.....(insturctions via internet) any suggestions? thanks for your h
elp
elp
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irf520 mosfet for cobra 29
- Thread starter Trainwreck
- Start date
Must have to be a member to find it.....i didnt find anything......oh well......all in due time i guess. But thanks for the help
this?
CB Tips and Tricks
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.
Channel 9 switch to Channel 19: Cut D32. Hard, huh?
CB Tips and Tricks
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.
Channel 9 switch to Channel 19: Cut D32. Hard, huh?
Wow....a whole 40W. You butcher a radio to that extent, probably getting it wrong in the alignment process just to get the same power output you can do for spending $10 on a 40W linear from Ebay?
Is there really any point to it?
Oh and BTW that mod will kill the finals you do put in because nobody seems to have noticed that you need to install a heatsink.
Yeah, yeah and we were supposed to install a heatseink when we started putting the 2sc1969 in a cobra 29 too. I never did and I know of at least three of them I did are still running strong. If you run a good sytsem, with no high reflect it will be OOOOKAY! besides mosfets are cheap cheap cheap, if it smokes it smokes.
Well all I can say is the modern cobra 29 is crap anyways I now own my second 29ltd chrome and just like the last one I had the final has gone bad and it seems like the MOSFETs are a heck alot easier to find online to order than the stock
I'm not a big cobra 29 fan but can say that I've used a few within the last several years and had no problems.
By running them I mean every day in a truck so it wasn't the most Cadillac environment for them and never had an issue. Yeah I agree the quality isn't what it once was but if you're losing finals so casually then something else must be wrong.
By running them I mean every day in a truck so it wasn't the most Cadillac environment for them and never had an issue. Yeah I agree the quality isn't what it once was but if you're losing finals so casually then something else must be wrong.