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Navaho TRC-458 Clarifier mod?

Robb

Robb

Honorary Member Silent Key
Dec 18, 2008
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Silicon Valley CA, Storm Lake IA
Can anyone give me the straight scoop on doing the open clarifier mod for this radio?

Or can any of the gurus guide me through it?

Done clarifier mods on many other radios before; just seen a lot of links on the net that didn't make much sense for this radio - is all.
 
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the mod is supposed to be in the CB TUNE-UP MANUAL MASTER EDITION VOLUME II if you can find a download of that??

There is a diode in the clarifier circuit that needs to be removed, to allow the clarifier to affect both the TX and RX. You also will need to change a few resistors, to give it a wider range. (There is one between pot & ground, and one between pot and + voltage. I used 100 ohms for both.)

another post says its the same board as the cobra 139xlr and says this for the clarifier mod:COBRA 138 139 XLR (OLD) PRESIDENT GRANT, WASINGTON,MADISON , ROYBN 510 , 520D ,TRC-449 457 AND 458

Unlocking the Clarifier
1)Cut R-117
2)Cut D-30
3)Find the backside of the clarifier knob.Follow the PURPLE and BROWN wires and cut them just before they connect to the PCB.
4)Solder the PURPLE wire to an 8 VDC source.
5)Solder the BROWN wire to GROUND.


that about all i could find
 
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yes it is the same as what you listed for Robb. it is the 858 pll unit. I just looked it up in master tech 2 and you beat me to it
 
Cut one end of D30 and jumper D29.
Cut the end of R119 that is nearest D29.
Solder jumper wire to cut end of R119 to cathode end of D44.
Trace the purple & white wire from the clarifier to where it connects to the pcb and cut it loose.
Re-solder this wire to the nearest pcb ground trace.
This should give you about 3khz down and 1khz of up slide.

The above was taken from CB TUNE_UP MANUAL MASTER EDITION VOL.2 page 20.
 
Unlocking the Clarifier
1)Cut R-117
2)Cut D-30
3)Find the backside of the clarifier knob.Follow the PURPLE and BROWN wires and cut them just before they connect to the PCB.
4)Solder the PURPLE wire to an 8 VDC source.
5)Solder the BROWN wire to GROUND.
Click to expand...

I used the first one that was posted. Working on three 858 chassis radios for local op. He gave me one of the radios plus he is giving me a fourth parts radio to keep. This guy has a dozens of 858 radios. I told him that I wanted to get one of these fine, old radios some day. So, for aligning/fixing these radios - he gave me one.

Thanks for the help, guys.
That clarifier mod worked.
 
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Robb said:
I used the first one that was posted. Working on three 858 chassis radios for local op. He gave me one of the radios plus he is giving me a fourth parts radio to keep. This guy has a dozens of 858 radios. I told him that I wanted to get one of these fine, old radios some day. So, for aligning/fixing these radios - he gave me one.

Thanks for the help, guys.
That clarifier mod worked.
Click to expand...
 
Hi Robb.. my name isRuss.. I have a Navaho Trc457.. and I’m ready to unlock my clarifier.. I read how to do it on ur page.. I just want to do it correctly.. so I know there’s other ways on here that show how to do it.. but I want to make sure I do it right.. is this the way to do it.. please let me know..
 
Russ Whiting said:
Hi Robb.. my name isRuss.. I have a Navaho Trc457.. and I’m ready to unlock my clarifier.. I read how to do it on ur page.. I just want to do it correctly.. so I know there’s other ways on here that show how to do it.. but I want to make sure I do it right.. is this the way to do it.. please let me know..
Click to expand...
See post #2
 
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Hi all, I have a Cobra 139XLR with the 858 chip, for the clarifier mod someone posted above for one of the steps to attach purple wire to 8VDC, can someone tell me where I can grab that 8VDC? Thanks for any help. Adam
 

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