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Cobra 148 GTL DX + Talk back stumper!!INSTALLED!!UPDATE

C

casios

Member
Apr 3, 2005
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Anyone know how to install talkback in this thing?....
everything with the 690010z board already has talkback in it.
With that said, I have looked at the procedure's to disable it in a radio with the tb in it and reverse them....with me so far? It does not work...I am sure there is something missing. I have tried clipping d-80 and the 1/2 watt resistor across the mic and pa with no results....
Just jump in here with what you got...The is an older trick about jumping the speaker to ground that may work but I cannot remember it...
good one huh?
Thanks
 

it should be D-90 in that radio ,and there is a spot you can put a 47K to 100K 1/4 watt resistor , my problem is that I have a diagram to go by and not a specific spot for you ,But D-90 should get you TB . Good luck to you Casio
 
Not sure the exact diode number, but usually D80. Clip that, then run a 5k-20k resistor from either pin 2 of the mic jack to the input pin of the audio chip, or run a 220k-3.3M resistor from pin 1 of the 4558 8-pin preamp IC to the input of the audio chip. One of those should get you the level you need.
 
I did it with D90 on a Grant GR , which was a clone of the old 146GTL DX .....should be the same ? put i just noticed the + sign there , maybe not. When I did do the TB on the GR , I honestly didn't like it much and it was a little bit much to do for talkback in the first place , I then just bought a ex speaker that had on/off talkback in it , it turned out to be the better way to go for me. Might even be cheaper that way if you have to take it to your local tech.
 
OK,
First off I do not see a d- 90...But do have a D-80. Clipped it...
This is the way I tried. Several different values of resistors...
to make sure I have the right pin on the audio its the fourth one, Right? From front of the radio to the back.
I ran from that pin to #2 mic...nothing then tried the first of preamp...nothing..

I have a galaxy 88 sitting here and looked on the solder side of the board and can see exactly what ya'll are talking about...because someone put a resistor there...But the 88 came with talkback so I can only assume that the resistor is there to quiet it down a little..

This cobra seems to be different though? Frustrating...
Did I do this correctly?
 
ok, Should I be using one of the ub-1 talkback boards in this thing or what?
thanks for all the help so far!
Cas
 
OK maybe this will help...
On other radio's you have two jacks in the back...
one for pa and the other for external speaker....
well this radio has one marked pa and the other marked cw key...
Anything there?
Thanks
 
DTB Radio said:
Not sure the exact diode number, but usually D80. Clip that, then run a 5k-20k resistor from either pin 2 of the mic jack to the input pin of the audio chip, or run a 220k-3.3M resistor from pin 1 of the 4558 8-pin preamp IC to the input of the audio chip. One of those should get you the level you need.
Click to expand...


Installed finally!!! The didode was d-75! After removing it I installed 1.0M resistor between the preamp and audio IC!
This project only took me 4 months to figure out!
This seems to be the same board as the connex 4800 dxl ECHO!
Thats where I found the schematic.
Thanks
Cas
 

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