disabling soundtracker(cobra29nwst)

frogman296 · Post by **frogman296** » Sunday 27th Jul 2008, 6:30

radio is

cobra29 nwst
pll cobra29ltd0442
made in china mfg date dec 2005

To disable the tx side of sound tracker..
1.Remove C-809 which is a 1.0uf cap
2.Remove C-819 which is a 1.0uf cap
3.Short pin #s 1&2

these are instructions i have found for disabling soundtracker. the caps i can handle...but what are these pins that have to be shorted?? are they the ICs in the soundtracker section?? there are 2 ICs in that area

one is a YD 31101
the other is a tc4066bp

Rick · Post by **Rick** » Sunday 27th Jul 2008, 9:43

The mod you have found will work, but the RX audio will still be interrupted by the ST.

The best way to do this is to remove C819 this should be a 0.22uf electrolytic cap (See diagram the Red X is where free the legs of the caps) then lift the leg of C37, which is, connected to Pins 2 and 3 of IC802 (TC4066BP) and connect the free leg of C37 back to where the positive of C819 was connected (I use a short bit of wire to do this, this is the Blue line on diagram). Sorry about the quality of the diagram but it’s the best I have.

Next go to the volume pot and find outer contact (This is the one which is not connect to ground) unsolder the wire from the main PCB, next find R40 (15K) remove it and replace R40 with 47K but leave the leg which is normally connect to the Base of Q801 and connect the free end of R40 to the wire from the volume pot.

Job done.

frogman296 · Post by **frogman296** » Sunday 27th Jul 2008, 12:45

okay i have a few questions

the caps...some run front to back, others side to side...

are the cap's negative side towards the final??

also volume pot, does this mean the main radio volume??

Rick · Post by **Rick** » Sunday 27th Jul 2008, 20:04

I do not have a PCB layout diagram for the radio, so I cannot tell you where the caps are.

If you can read a diagram, it is easy to see what I am advising you to do.

To find the cap C819 just follow the track from the Collector of TR17, it goes to two components, one his the cap you are looking for, and the other one go to resistor R84.
Just un-solder and lift the leg of the cap C819 which has connected to the Collector of TR17, now solder a wire in to the hole where you have un-soldered the leg of C819 from.
Next find C37, this is connected to Pins 2 and 3 of IC802 (TC4066BP), just un-solder and lift the leg of the cap C37, now solder the free end of the wire to the free leg of C37. Its that easy.

Yes, it is the main volume control I am talking about.

frogman296 · Post by **frogman296** » Monday 28th Jul 2008, 0:50

okay thanks rick for your help.

i will keep in touch.

frogman296 · Post by **frogman296** » Monday 28th Jul 2008, 7:23

well...i tried this...and now i have no swing..

Rick · Post by **Rick** » Monday 28th Jul 2008, 7:33

This is because you have done something wrong.
Make sure the collector of TR17 is connected to C37.

frogman296 · Post by **frogman296** » Tuesday 29th Jul 2008, 9:03

Rick wrote:This is because you have done something wrong.
Make sure the collector of TR17 is connected to C37.

okay..near as i can see...i have lifted the wrong leg of c37.

i have decided to scrap the radio...but...i am going to use this radio to hopefully perfect this mod.

frogman296 · Post by **frogman296** » Tuesday 19th Aug 2008, 6:17

http://cbtricks.com/radios/cobra/29ltd_ ... 1_pg11.pdf

on page 11...the component side of the board...i have decided to try this again...any help would be appreciated...

frogman296 · Post by **frogman296** » Tuesday 19th Aug 2008, 7:05

hmmm...i have been retracing all steps...the wire from the volume control...just may be the mistake i made...

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disabling soundtracker(cobra29nwst)

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