adjustments on a 29 ltd

[loosecannon]

first make sure you are using a power supply that can handle the increased wattage of the mosfet mod.
should be at least 5 amps continuous.

i have never done a mosfet mod the way your instructions say to, but thats not to say it wont work just fine like that.

i have always used the EKL instructions on cbtricks and made my own companion part from the instructions on the same site.

there is no bias control on the 29LTD so that wont be it.

D11 should be intact. turning up VR4 basically does the same thing.

my guess is that being new, you are not doing the tune up properly.
no offense intened, its just one of those things you get good at after doing it many times.
make sure you are speaking into the mic when you make the adjustments.

the way your radio is acting sounds like the tuning was done for max deadkey with no modulation.
when this is done, you get a high deadkey, but the transmitter has no room for the modulation.

turning L14 is not the way to lower the deadkey. it is an impedance matching device and when its peaked. the impedance is matched.
to lower the deadkey, do the swing mod: Cobra 29 LTD super modulation modification

try doing the tuning again for maximum while modulating.

good luck,
LC

 

[zebbman]

last question. should my dead key rise when i turn up the dynamic on the radio

 

[Robb]

The mic gain should only affect modulation; not power output. Put you hand over the mic in a quiet room and key the mic - and there should be no change in dead key power output.

Did you get this radio used - or new?

Ask all of the questions you want to - BTW...

 

[zebbman]

used radio, when i turn up the audio the dead key also goes up. i thought that was wrong. im thinking of just putting it back to stock if i can and doing the mod the cb tricks way. thats if i can figure out how. do me a favor if you will and read over how i did the mod. is all that necessary? cb tricks way changes 3 parts and this one changed 8 i think. that mod said to remove r55 which i did but i put a cap in its place. im starting to wonder if all this was necessary. i may just use this as a parts radio and pick up a different one

 

[loosecannon]

most likely you are experiencing oscillation of the final.

this can happen with mosfet conversions.

the 29ltd has been made for so many years that its next to impossible to make a conversion that will work in EVERY radio.
you might just happen to have a model that is not compatible with that particular mod.
there are probably one or more parts that need minor value adjustments to get it just right, but this is not the type of experimentation i would suggest to a beginner.

your best bet is to put it all back to stock, get the EKL companion part, and do the mod on cbtricks.
LC

 

[zebbman]

is there supposed to be a tuning slug in L16?

 

[zebbman]

ok, gonna put it back to stock. i just need the values for the following

C53
C126

 

[Robb]

C53 = 50v RH J% 68pf
C126 = 50v RH J% 22pf
http://www.cbtricks.com/radios/cobr...st/graphics/29ltd-st_29wx-st_sm_pg12_pg34.pdf

 

[zebbman]

thanks again. your help here has been well beyond what i expected anyone to give a novice like me. maybe i picked the wrong thing to help pass my time. being stuck in the house day after day gets a little boring and i had hoped this would be a good hobby.

 

[Robb]

thanks again. your help here has been well beyond what i expected anyone to give a novice like me. maybe i picked the wrong thing to help pass my time. being stuck in the house day after day gets a little boring and i had hoped this would be a good hobby.

Oh, it can be a nice hobby.
Once you get out of the gate.

I recommend any decent AM/SSB radio. To ask any 20 different people would probably yield 10 different answers - as to which one is best. Early Cobras and Unidens are fine; export radios have a lot of extras. IMO - you will get a lot more out of the hobby in the long and short run with a SSB radio.

Not everybody fixes their own stuff. I have done only enough of that to get my feet wet; to get familiar with the circuits, parts, and functions. Not everybody goes that far. I think you are off to a fine start.

A lot of guys just find a trusted tech that is close by to do their work for them. You would be surprised how many do just that!

 

[zebbman]

i have a few different radios but i really like to know what makes things work. i got this to do just that. that way if it didnt work or if i blew it up it wouldnt matter. now the trick is to get it back to where i can put the en1230 in and see what happens. i think i only need to replace those 2 components. i have a 148 and a galaxy 979 that i wont touch. i cant drive so getting out to find a tech is somewhat of a problem. i read alot which helps figure things out.

 

[Robb]

I attempted to put a MOSFET in a TR-696 FD-1 - and it wouldn't take. Tried 2 more times - and 'no go'. So; I put it back to stock and it works fine. Some radios won't take the mod - as LooseCannon said. LC is a radio tech and works on this stuff all of the time. His experience is invaluable as he helps out a lot here on the forum. There are others - too - that do this here.

If you want to find out why it won't work for this radio; this project might take even more time and digging. Not to dissuade you, just keep asking questions here. Someone is bound to have dealt with the same difficulties you face, and this may provide answers for others. We have thread after thread of such scenarios, and the answers often come out eventually...

 

[zebbman]

i will keep plugging away. i was so darn pleased it just worked after i did the mod you have no idea. then just as quickly disappointed it didnt work right. but it did work. i may buy another 29 to try it on if the next attempt doesnt work out. i know alot of people ask why even bother. im not doing it to be the biggest or loudest kid on the block. i just want to see if i can. for me its alot to accomplish. believe me

 

[zebbman]

any other possible replacement parts that would closely match c53 and c126?

 

[zebbman]

gonna send my buddy to radioshack to see if they have those 2 caps