Cobra 200GTL - Lost High Power On SSB

[CollinsMan]

I was talking on this radio a few minutes ago, and lost high power on SSB. One minute it was peaking at about 100 watts, and the next moment, it dropped back to about 20. On low power, the radio still puts out about 16 or so watts. I've never done anything to the radio other than the frequency mod.

High power on AM and FM remain the same at about 30 watts carrier. Low power is about 3 watts.

SWR is 1.2:1, and the Astron RS 70M power supply doesn't break a sweat at a steady 13.8 Vdc out.

Has anyone encountered this problem before? I'd really appreciate any pointers before I get serious with it! :twisted:

 

[BIONIC_TEXAN88]

oh yeah, too many times I have heard this. happened to me also. You probably lost you driver going to the 2 pills. The 200's are notorious for that.

 

[park]

Mine does that sometimes, after turning the radio off then back on fixes the problem for awhile.

 

[dxhound]

I have a 200 here that does the same thing. Works great on am fm and low power side band. But when I switch to Hi power it works for about 15 seconds then slowly drops to zero. After about 20 seconds I can repeat it. It seems there is a transistor and AlC circuit devoted to HI power sideband. The problem would have to be there as all other modes low or hi work fine. I looked at the audio coming off the Ta2227 Audio amp and noticed the audio output drops to zero to coincide with the wattage out. But the audio is good which leads me to believe that the ALC is over compensating and choking off the audio in Hi power. That is all the testing I have done to give you a heads up. Ill post more when IO get time to look more.

 

[CollinsMan]

I appreciate the replies, y'all. Right now, I've relegated the Cobra to the "shelf of shame" that contains all of the "problem" gear.... I'll get to checking out the ALC and driver circuits when I am a little less aggravated.

DX Hound, I'd really appreciate it if you would let me know what you find out about the ALC circuit. I enjoy the Cobra, and would like to get it back on line. I guess I'll have to make do with my old FT 101 until then.

73

 

[john boy]

I had the same problem.twice,,,replacing Q73 fixed it