cobra 148 NW ST/ no am tx, ssb tx is fine

[BIONIC_TEXAN88]

any clue what would have caused no am tx, but ssb tx fine? the tx/rx lights red when I press the mic. mic is tested and works fine on my other radios.

 

[Switch Kit]

AM Voltage regulator ? pretty sure you can get a replacement at Rat Shack.

 

[BIONIC_TEXAN88]

Thanks jim, excellent pic, I need to find the number on the regulator in case I need a cross reference for a part at rat shack.

 

[Switch Kit]

D1135 and NTE291 there are others as well , there are even stronger ones that will work , IM just not sure on the numbers on those.

 

[BIONIC_TEXAN88]

jim, ok I went to rat shack but didnt find any of those numbers for a regulator. I bought one thats a 12vdc regulator. I put it in and now I have a good solid 5w dk but no swing. the am power has no adjustment, the dk stays the same.

I had this problem once before on a 148 and it ended up being the voltage regulator. is there another regulator on this board?

 

[Switch Kit]

hmmm , now you have watts but no swing , would I guess to say you have no audio on AM but it appears that you do on SSB ? It's been a long time since I got the part replacement from Radio Shack on one of those ,so the numbers avail me ? Whatever they were ? they fixed a C-2000 and a 148GTL at the times, IM sure someone else with more experiance with these radios should key up on your thread. Wish I could have helped you more Tex.

 

[bob85]

its not a regulator as in a 7812 regulator ic, it is a regular pnp transistor used as a switch for SSB and as part of a regulator/modulator amp in AM, not sure about the one used in the later american radios but oures had a 2sa1012 with a 2sb525c and 2sc945 ssb switch, the dual final radios used a 2sb754 with a 2sa473 and a d471l for SSB switch,
people here used to blow the 1012 running them flat out on FM, i uprate the single final reg/mod circuit to the dual final parts and they handle the strain much better.