New Victim! (project) Realistic Navaho TRC-457

[metalguy66]

She already works like a dream despite being a little rough on the cosmetics.

I'm gonna replace the Electrolytic Caps, the heatsink insulators & paste, clean the pots, check all the voltages & signal levels, and give her a good general cleaning. After that, I'm open to suggestions.

 

[Shadetree Mechanic]

I believe that has an 858 pll, @unit_399 has a wealth of information on the radios that use this chassis.

HOME | 858ssb

unit399.wixsite.com

Mod for 5kc steps.

5Kc Steps for UNIDEN 858SSB Chassis

With more operators using export or amateur transceivers for 11 meter dxing, the use of frequencies 5 kc below the standard cb channels (i.e. 27.400 instead of 27.405) is becoming popular on single sideband . Typically, operators with regular cb rigs "unlock" the clarifier control and swing the...

www.worldwidedx.com

 

[dave457]

I owned one for a long time, only thing I didn't like as it had no mic gain control

 

[Shadetree Mechanic]

Install a frequency counter.

FINALY PURCHESED A MADISON.

Granted it's not the president but the final edition Madison with the digital clock. I'm gonna have my Tec unlock clarifier, add upper and lower and change out the digital clock with a frequency counter. I would like to add the counter that fits perfectly and looks like a factory install. I...

www.worldwidedx.com

 

[wavrider]

Trc 457, Trc 458 great rigs shine on SSB.
Mic gain VR is on the board.
Easy freq expansion, one of the best receivers out there for 11 meters..
do not try to squeak every last watt out of the radio, keep AM deadkey low so you do not stress the components.
tons of info on WWW
I think cobra 139XL is same board if you want mic gain control on a knob

 

[metalguy66]

Thanks to all who posted! I am doing the recap now, I'll read all the great links & info in the meantime and check back in when I start doing mods..

 

[nomadradio]

The schematic for the Cobra 139XLR reveals that a 20k audio-taper pot and shielded 2-conductor wire provide an external mike gain control when wired in place of the TRC radios' trimpot.

Just have to decide where to mount it. Could always use the "dimmer" control position, unless it's already wired for AM carrier-power control.

73

 

[metalguy66]

Ok.. From left to right: Lo-pass audio filter on/off, Extra channels on/off, Extra channel bank selector knob, Freq counter with channel bank indicators below it, Modulation meter, Mic gain knob. There's also a 10-turn potentiometer in the clarifier circuit now.

The freq counter is not hooked up currently. It is causing noise in the audio amp at the moment. If I am unable to resolve this, I may end up converting the entire radio to negative chassis ground. Hopefully, I don't end up having to do that- It's quite an extensive mod and I'm trying to keep everything on this unit "reversible".

 

[rdsawyer]

Could one of you guys supply me with the TRC 457 / 458 relay part number 3PDT 12 vdc coil, thanks

 

[doffo]

There is a specific tantalum capacitor to replace on that board. Better to get a higher voltage rated one as its already working near its limits. MikesRadioRepair has a video on the Cobra 138 XLR restoration tips, and has the one to replace. I took a screenshot for ya. Circled in red.
I used a good quality Vishay 2.2uf 50v cap. Though, others might be just fine. Polarity matters, so make sure it gets installed the right way.

 

[doffo]

Nevermind... Scratch that idea....... I see it isnt even there on your picture and a couple others online. My TRC-449 mobile and the TRC-458 have that tantalum cap in place. Hope that info helps someone else who have similar radios.

 

[nomadradio]

Could one of you guys supply me with the TRC 457 / 458 relay part number 3PDT 12 vdc coil, thanks

A search for type "MX3P relay on fleabay turns up multiple hits. Here's one of them:

https://www.ebay.com/itm/1509576964...d=link&campid=5336136228&toolid=20001&mkevt=1

73

 

[rdsawyer]

Bingo! that's the one. I have ordered four ice cube relays for this rebuild all of witch was slightly too big. the total spent on relays is about $75 i should have ask long ago. Thank you so very much for the help 73's N4VWD

 

[Roadrunner69405]

Nevermind... Scratch that idea....... I see it isnt even there on your picture and a couple others online. My TRC-449 mobile and the TRC-458 have that tantalum cap in place. Hope that info helps someone else who have similar radios.

There is a specific tantalum capacitor to replace on that board. Better to get a higher voltage rated one as its already working near its limits. MikesRadioRepair has a video on the Cobra 138 XLR restoration tips, and has the one to replace. I took a screenshot for ya. Circled in red.
View attachment 67335I used a good quality Vishay 2.2uf 50v cap. Though, others might be just fine. Polarity matters, so make sure it gets installed the right way.

Thank you very much for your share. I just bought an old TRC 457 last night for $50 and after cleaning on it for an hour that tantalum cap popped. Do you have any idea what would cause this. Just wondering if it will pop again when I replace it.thanks

 

[doffo]

Thank you very much for your share. I just bought an old TRC 457 last night for $50 and after cleaning on it for an hour that tantalum cap popped. Do you have any idea what would cause this. Just wondering if it will pop again when I replace it.thanks

Was it while transmitting? I think that would of been the only time it would do it. It is already working near its limits from what I understand, so it probably called it quits and let go.