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R123 on cobra 29 ltd classic

1iwilly

1iwilly

Sr. Member
Dec 7, 2008
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hello to all i have a cobra 29 ltd classic china made 1995 all the info i find where it says to replace R123 to a .47-ohm resistor. when i put in .47-ohm resistor i have no power output R 123 resister on my meter reads 1.5-ohms. the same scenario on my Realistic trc-427 says to change R-61=1-ohm resistor to a .47-ohm no power output ?? thanks
 

Hoo boy...

1iwilly said:
when i put in .47-ohm resistor i have no power output R 123 resister on my meter reads 1.5-ohms
Click to expand...

What wattage are you using?

You may have blown the Final by doing this - especially if R56 (22 ohm) is messed with...

The Final can blow from forced switch - by too much RF - can't replicate a signal when it sees itself being flooded by RF - thinks it will turn on and stay on...until it goes poof...

Hey! R123 Too low, you can blow the Base from TOO much power being rectified (applied) to the base and it blows from the ratings being exceeded.
  • It actually works better (more Linear) if you INCREASE the value to 2 to as high as 5.6 ohm - and tweak R56 to a lower value as needed
If you have a Drawer full of 2078's - do what you want, but no power out is a sign that the Final blew.
 
And another perfectly working radio was sent to heaven due to the dumbass golden screwdriver brigade trying to make them run power they were never designed to with an increase that's barely going to get an extra S point to the other end, assuming of course that the extra power is actually going out on the channel you're transmitting on, not spread over several either side a well as 81Mhz..

If you want more power then buy a linear amp. The best you'll ever do without one is double the power, an extra S point to the other station but running the stock PAs to screaming point and leading to their premature death, that's assuming they don't die in your attempts to wring every last milliwatt from them.
 
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no the final is ok i just couldn't figure out why exchanging the value to the recommended one when i key up no power output shows on meter put the original back on power is back just trying to squeeze that extra 1/8 of a watt to make my eyes happy LOL
 
Too much power would turn it on like a switch - saturated...why you lost power - TOO much signal...

Thank you for realizing that no power may mean somethings worng and you stopped before it did the Murphy thing...

upload_2020-7-19_14-59-1.png​

You'd be better off playing with the "Cap" values by R56 instead...
 
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1iwilly said:
no the final is ok i just couldn't figure out why exchanging the value to the recommended one when i key up no power output shows on meter put the original back on power is back just trying to squeeze that extra 1/8 of a watt to make my eyes happy LOL
Click to expand...

There's probably an adjustment in the watt meter. :)
 
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1iwilly said:
no the final is ok i just couldn't figure out why exchanging the value to the recommended one when i key up no power output shows on meter put the original back on power is back just trying to squeeze that extra 1/8 of a watt to make my eyes happy LOL
Click to expand...

it's why I asked about the wattage - meaning the rating of the resistor.

IF it's 1/4-watt it may, or may not, blow open saving your work from destruction but smaller wattage ones will blow open - luckily it can save a project because it's about as cheap as the fuse.

So if the resistor being 0.47 ohm, was a larger READ: Greater Wattage dissipation / Rating - it would hold up to the inrush and the current it uses to generate the power will/could potentially blow the Final instead.

Not_Trying_To_Beat_You_Up = ON.
Beating_A_Dead_Horse= ON.
Schrödinger's_Cat=Off

Part of the problem with mods like the ones you came across, it's the issue of knowing all of this BEFORE you swap the part in, can save you from making this same mistake - over and over again ... Seen this happen many times and I used to just let it go and replace the part, but these days, everything being at a premium - the "it's on me" repair jobs are not why the guy that fixes the radios he sells - is in business anymore.
 
it's the same way people take a very expensive car they just bought and start modding it we are never satisfied but in my case, i like to show off how bad my barefoot radio is compared to the other guy's barefoot radio when there is no skip rolling and you're hanging out with friends and bored so we have a barefoot contest in modulation and watts. no other reason

M0GVZ said:
And another perfectly working radio was sent to heaven due to the dumbass golden screwdriver brigade trying to make them run power they were never designed to with an increase that's barely going to get an extra S point to the other end, assuming of course that the extra power is actually going out on the channel you're transmitting on, not spread over several either side a well as 81Mhz..

If you want more power then buy a linear amp. The best you'll ever do without one is double the power, an extra S point to the other station but running the stock PAs to screaming point and leading to their premature death, that's assuming they don't die in your attempts to wring every last milliwatt from them.
Click to expand...
 
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Some people strap a large turbo on a stock four cylinder Honda long block, can it be made to work?? Yes... but for how long depends on many factors...

Like Andy mentioned the 22 Ohm resistor is the one that should be played with (value modified) if you are on a mission to burn some parts up while learning how to liberate a few watts.

Too much drive can be detrimental.
 
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