Cobra 19 LTD

[Demon29]

i picked up this old cobra 19 LTD, now i would like to add talkback to it, but this radio wont accept the poor mans talkback as ive seen it called before (the resistor across the ext speaker and pa), now yes i know i can order a universal talkback board and all of that but id like to see if there is another way to add talkback without buying a new circut board to install, i dont care if its a vairiable talkback or not so just let me know if there are any other ways to do it, thanks

here is a pic of the radio too...

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[Night Crawler]

this radio wont accept the poor mans talkback as ive seen it called before (the resistor across the ext speaker and pa)

There are a couple of ways to do it to the 19LTD if you can get access to the back of the mic jack that's mounted on the front panel put the resistor between pins 1 and 4.

Another way is to find the negative side of the speaker and connect one side of the resistor to that then run a wire to the other side of the resistor and connect it to a ground point on the circuit board (the ext speaker or pa jack ground would work for that)

[Demon29]

thanks a ton!, i was told by a friend to try the mic port but i had never heart the speaker one

[Night Crawler]

I'll explain what the PTT switch does on the mic
In the receive position it just grounds the negative side of the speaker to the circuit board through the mic cord, plug and jack on the radio.

When you add the resistor even when transmitting the negative side of the speaker is put to ground except through a resistance and that resistance value is chosen as not to cause feedback the higher the value of resistance the lower the TB will be.

After looking at the schematic for the 19LTD I could see why the EXT/PA connection would not work the external speaker jack is wired in series through a resistor to the internal speaker in the 19LTD.

I don't think one of those universal TB would work with that radio just do it either way that I explained and it will work fine.

[Demon29]

thanks a ton, i hope to try that today!

[Demon29]

When i try this i need to remove the existing negative wire to the speaker, and then run a wire with the resistor from the negative to a ground on the board

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Monday, 11 March 2013, 21:20 PM

Well i got it, i wound up doing the resistor between pins 1 & 4, i tried the speaker to ground with no luck, found out after i tried the resistor at the mic pins it wasnt the right ohms for the talkback to be hear, so i upped it and it works great now, after i did that i hooked up one of my echo mics to it and it sounded great, thanks again for your help!