COBRA 25 NW ST POOR RX

[speedracer6g]

I am working on a Cobra 25 nw st. It had carrier with no tx modulation and no rx. i traced the transmit problem to a burnt d10 diode and burnt modulation transformer. i replaced both items plus the audio chip. no transmit works fine but i have very poor rx i have to turn my monitor up to 85 uV to get it to register just below 1 on the signal meter. i replaced tr1 and teh 2 1n4148s on the rx input and also replaced the 2 schotky diodes and ran through a rx allignment. i still have poor rx if anybody has had this problem or has any ideas let me know. i think this problem all started with a jumper on d9 or d10 the clipping diode. this caused that feedback problem i have herd about and well the rest is history. any help would be great

thanks,

MIKE

 

[Switch Kit]

Had the same problem and did the same thing you have up to this point Mike , after hours of trying to figure it out , the radio became a parts radio. this is also when I learned and through further investagation , jumping the anti-spiking diode is a NO NO ! it's just not worth the extra watt you might get out of the radios.I was very surprised to see that even DTB jumps those diodes ? Go figure ? There there for a reason. Although he does mention about the RX at higher volumes. This has been a few years for me now , and after reading why it wasn't a good idea , I steer clear from the jumping of that diode.It's not worth it in the end. I suggest if somebody wants more power with these cb radios , buy an amp or figure out a good mosfet mod on them. Good luck to you Mike , I hope you figure it out. Peace

 

[speedracer6g]

Yep i used to jump the diodes until i found out what happens and it realy dosnt get you much. i had this radio laying around and got the transmit side to work but the receiver dosnt open up until u start pumping about 81uv into the receiver. on the brite side i got the new ERF2030 mod working great on the cobra 25s there is a couple of things i had to do but i am getting about 19 watts with no clipping AVG rms. wich is better than some of the 2sc1969 by a couple of watts. butt the only problem is i still only have about 7 watts deadkey i would like to get 12 or better. I have to tweak the biasing on my 29 setup yet before i write anything up on them to. i figure i will post some stuff up here on the forum to help some other guys out too.

MIKE