Radio Make and Model: cobra 148 gtl
PCB Number:philly made 1993
PLL Number:rci 8719
i got this radio a while ago it has low modulation when all the limiter are intact radio dead keys 2watts swings to 3 1/2 if i cut r131 then it swings to 8 watts on a bird
i try the 1k resistor to middle leg of tr24 i try tr26 too no luck i've change tr41 upgrade one tr 42. also ssb is fine no modulation problem only on am
i even change tr 23,tr24,tr24,tr26 no luck i also change r124,r126 to 4.7k and r131 to 4.7k no luck. thanks
need help from the 148 gtl experts.???
Re: need help from the 148 gtl experts.???
You'll get more chance of a reply if:
1) You don't try to put lots of sentences into one. Punctuation, paragraphs, and correct capitalisation make things much easier to read for someone to help you.
2) Do a bit of basic research first. Try Google.
3) Learn a bit about what you are trying to archive. How are you measuring your "low modulation"? Have a look athttp://www.radiomods.co.nz/forum/viewto ... f=1&t=2914 for more info on this subject.
Good luck with your problem.
Sue
1) You don't try to put lots of sentences into one. Punctuation, paragraphs, and correct capitalisation make things much easier to read for someone to help you.
2) Do a bit of basic research first. Try Google.
3) Learn a bit about what you are trying to archive. How are you measuring your "low modulation"? Have a look athttp://www.radiomods.co.nz/forum/viewto ... f=1&t=2914 for more info on this subject.
Good luck with your problem.
Sue
Re: need help from the 148 gtl experts.???
sorry about that.
i was trying to explain all the stuff that was already done to the radio.
so i don't get hit with change this change that.
i'm using a bird meter. i also have the sams photofacts.
i was trying to explain all the stuff that was already done to the radio.
so i don't get hit with change this change that.
i'm using a bird meter. i also have the sams photofacts.
Re: need help from the 148 gtl experts.???
i forgot to add,i also have a multimeter,and a 6 amp power supply.
- The Defpom
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Re: need help from the 148 gtl experts.???
Check the voltage drop across R111 (tell us the voltage on both sides of it, in TX and RX), I have come across issues on this and similar chassis where a capacitor is loading down the DC supply causing a large voltage drop across that resistor, it sounds similar.
Re: need help from the 148 gtl experts.???
OK on one end of the resistor, i have 7.94 volts, the other end reads 8.34 volts this is on RX. on TX they don't change.???The Defpom wrote:Check the voltage drop across R111 (tell us the voltage on both sides of it, in TX and RX), I have come across issues on this and similar chassis where a capacitor is loading down the DC supply causing a large voltage drop across that resistor, it sounds similar.
- The Defpom
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- Joined: Friday 20th Aug 2004, 18:06
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Re: need help from the 148 gtl experts.???
That sounds fine at that point.
Re: need help from the 148 gtl experts.???
thanks to all that replied.
i think i found the problem when i was doing the 1k resistor mod. i was doing it to the middle leg of TR26.
after re checking it suppose to be TR24, now i have full swing in am.
i think i found the problem when i was doing the 1k resistor mod. i was doing it to the middle leg of TR26.
after re checking it suppose to be TR24, now i have full swing in am.