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

Thank you. Another very informative post.

A very informative post. I am actually saving up to buy a scope. I may have one next month. I just fix and tweak cb radios as a hobby. I don't have any courses on electronics but I have been sort of teaching myself stuff and asking questions as I go along. I have a Palomar 225 (http://www.firecommun...

On the website http://www.shadowstorm.com/cb/CB_Myths_Exploded.html the guy says that "An AM signal is fully modulated when the "swing" doubles the carrier. That is to reach 100% modulation a 4 watt key should swing no more than 8 watts. Anything more than that is distortion to your v...

OK. I tried it again. There is a difference but its minimal. I have a theory though. Maybe my radio is out of alignment and most of the power is going out across 10 channels. I think that might acount for it. I'm getting a scope in a few months I hope so that should help. assuming I can teach myself...

I have a cobra 29 that I modified. (1 watt dead key, 15 watt swing. stock final) And i recently aquired a palomar 225. I also have a Dosy libra 631 swr/watt/modulation meter. I have this setup as my base station. Anyway the meter says that (with the amp on) I have a 30 watt dead key swinging to 150 ...

Well, I found it. It was so simple too. I should have seen it earlier. It was a bad Dynamike knob. That was simple.

Radio Make and Model: Cobra 29 LTD ST PCB Number: KEPC-255-C PLL Number: D2816C Test gear available: Digital Multi-meter, watt meter, modulation meter (trying to save up for a scope) Symptoms: If i yell into the mic then everything is good. Modulation goes up to 100% and power swings to about 9 watt...

Has anyone got any mods for a Jana KJCB-440.

I know the 2sc1969 was a very popular mod for most CBs before they were discont. The 2sc2312 has a slightly higher output.Is this a good final for the coba 29. I can't see why it wouldn't work. i just wanted to make sure before I buy a few.

Thanks for the input guys. I was just curious.

Is it possible to to modify a cobra 29 to take a MRF454? Has anyone tried?

I was browsing through transistor specs and came across some cool looking transistors. I was woundering why someone couldn't put a MRF454 final in a radio such as the cobra 29, or is it posible? and would it require a lot of modifications. This thing puts out 80 watts. I have never taken an electron...

Hi Rick. Thanks for all your help. I really didn't think it was the driver but sure enough it was. now my radio is pushing 20+ watts. Thanks again. I learned a lot in the last few days.

TR16 B=0.75 C=7.7 E=0.35 TR15 B=0 C=13 E=0.32 (I think these are the right pins, I might have E and B switched.) TR14 B=0 C=13.2 E=0 I know there is a problem here somewhere. There is a 2.7ohm resistor at R58. This is a common mod and I think that's why I have voltage at E on TR15. But I don't quite...

YEP. All voltages are correct.

Sorry. Channel 1 - 2.26V, channel 40 - 3.01V

I don't own one but I have read the the 200 gtl dx comes with a factory switchable talkback. It uses the echo on/off switch to activate/deactivate it.

RX - 1.62V
TX - 2.26V

Sorry Rick, but TP1 is not not used in my radio. My radio is actually a 29 nw st. Which as far as know is pretty much identical to the LTD. Or it may even be a LTD NW ST. However, IC1 has 29 LTD printed on it. With that said if TP1 is supposed to be empty then it has no voltage, however, I have volt...

Yeah I am beginning to think that Rick could build a CB from scratch and improve on many manufacturers designs. A genius. And if he had my radio, it would have been fixed 20min after he looked at it. But I have to make do with my knowledge and rely on people on the net because the there is nobody wi...

My ic3 is good, my driver is good and my final is good. what would i check next?

I am also having the exact same problem (may be a different cause). If you have any luck finding that gremlin, I would like to fix my radio too.

Great site! Thanx.

HI. I am new to the world of cb modification. I have 2 Cobra 29 NW ST's that I want to modify. Are the mods the same as for the cobra 29 LTD's?