1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Realistic trc 458 no receive no transmitt help

Discussion in 'General CB Services Discussion' started by drking, Apr 19, 2017.

  1. drking

    drking
    Expand Collapse
    Active Member

    Joined:
    Jun 9, 2015
    Messages:
    8
    Likes Received:
    0
    Hi guys been on this forum quite a while an found it very informative hope u guys can help got a realistic Navaho 458 no receive or transmitt but have sound in the speaker as I live in Jamaica the service manual is not available so what could b the problem or problems


     

  2. sonoma

    sonoma
    Expand Collapse
    Well-Known Member

    Joined:
    Sep 14, 2005
    Messages:
    1,210
    Likes Received:
    378
  3. drking

    drking
    Expand Collapse
    Active Member

    Joined:
    Jun 9, 2015
    Messages:
    8
    Likes Received:
    0
    Thanks Sonoma any advice on where the problem is or a fix
    t
     
  4. Tallman

    Tallman
    Expand Collapse
    W9WDX Amateur Radio Member, KW4YJ EXTRA class

    Joined:
    May 1, 2013
    Messages:
    1,352
    Likes Received:
    636
    Is there any activity at all? Lights, meter moving? What kind of noise?
     
  5. drking

    drking
    Expand Collapse
    Active Member

    Joined:
    Jun 9, 2015
    Messages:
    8
    Likes Received:
    0
    I have no meter movement just some noise that sounds like ash
     
  6. Robb

    Robb
    Expand Collapse
    Yup

    Joined:
    Dec 18, 2008
    Messages:
    9,924
    Likes Received:
    1,861
    TRC-458 common problems:

    1) C179 2.2uf 16v tantalum cap. Replace with a 2.2uf 25v electrolytic. This cap is often found failed or failing. Replace.

    2) Ribbon cable from board to channel selector/LED channel display. At the board end of this cable where it slides into the receptacle is often dirty and corrosion is present. Clean off the cable end with a ScotchBrite pad or fine steel wool until all corrosion is removed. Must use care so as not to ruin this delicate and hard to replace cable. Clean the socket with very fine sand paper (500 or 600 grit) - lightly sanded - and douse with electrical contact cleaner and blow it out with compressed air.

    Make a wedge of a thin piece of flat scrap plastic (about ~.030" thick) with the same length of the inside of that socket. Slide the cable into the socket and then gently wedge that piece of plastic behind the cable into the socket in order to force the cable to make contact. Have seen this issue with the four or five 458's that I've worked on and is the only fix that is simple, easy, and effective.

    If this cable doesn't have proper contact to its socket; you will have nothing out of the radio. Receive and transmit will not work. Common problem.

    3) Clean the relay contacts by carefully removing the relay cover and spring and careful not losing the spring when you remove it. Use a clean paper Q-tip with the cotton end removed with electrical contact cleaner between the six contacts on the relay body. Do NOT use a file OR sandpaper, as these contacts have a special surface on them that must be protected. Clean the floating contacts with electrical cleaner and a clean paper card - like a white matchbook cover. Reassemble. If this is damaged, it is hard - but not impossible - to replace.

    4) Check with CB Tricks to see if your radio has the Service Bulletins issues dealt with. The Cobra 139XLR is practically the same radio and many of the Service Bulletins won't be necessary because the 458 had them dealt with already. But I'd check to be sure.

    Just finished rebuilding a TRC-458; pictures and story forthcoming . . . film at 11 . . .

     
    #6 Robb, Apr 19, 2017
    Last edited: Apr 20, 2017
    Klondike Mike and LeapFrog like this.
  7. Tallman

    Tallman
    Expand Collapse
    W9WDX Amateur Radio Member, KW4YJ EXTRA class

    Joined:
    May 1, 2013
    Messages:
    1,352
    Likes Received:
    636
    Well there you have it! ROBB is the expert with no peers of his equal.
    ROBB: I'm not being mean or sarcastic either.
     
  8. Robb

    Robb
    Expand Collapse
    Yup

    Joined:
    Dec 18, 2008
    Messages:
    9,924
    Likes Received:
    1,861
    lol.
    That's me w/o coffee.
     
  9. drking

    drking
    Expand Collapse
    Active Member

    Joined:
    Jun 9, 2015
    Messages:
    8
    Likes Received:
    0
    Looking for the c179 can't seem to find it wonder if Klondike has a kit for this radio
     
  10. sonoma

    sonoma
    Expand Collapse
    Well-Known Member

    Joined:
    Sep 14, 2005
    Messages:
    1,210
    Likes Received:
    378
    Robb gave you about all of the main problems with this radio except for the caps more than likely need to be changed since they are about 30 years old.
     
    Robb likes this.
  11. sonoma

    sonoma
    Expand Collapse
    Well-Known Member

    Joined:
    Sep 14, 2005
    Messages:
    1,210
    Likes Received:
    378
    you might even find a few of the VR's to be bad in the final stage area. you need to see if the PLL is even locking on , this will also cause a problem of a dead radio if you have any bad solder joints in the PLL and VCO area.
     
  12. Robb

    Robb
    Expand Collapse
    Yup

    Joined:
    Dec 18, 2008
    Messages:
    9,924
    Likes Received:
    1,861
    I also replaced the AM Regulator and the two transistors on the aluminum panel on the back.

    Two white LED's in the meter looks outstanding and is cheep to do! Removed the red transmit light altogether and used its mounting location for the second white LED. The red TX light obscures the meter movement when transmitting = annoying to me.

    A LOT if useful info on unit_399's site; I used the mod to improve the AM audio by adding an electrolytic cap and a 1N914 diode to make the AM modulation better. Also replaced the 2SC1306 with a 2SC2166/driver:
    http://unit399.wixsite.com/858ssb

    Put in Schottky diodes in too.

    Took out that nasty 5 pin DIN plug and installed a standard 4-pin male plug with the standard Cobra wiring.

    Used Klondike Mike's cap kit to recap the radio. Also replaced all of the tantalum caps.

    Radio now will dead key 4w and swing 30w with Xit13's MOSFET mod. A cheap and very useful mod! Cost about a nickel to roll your own biasing device and the IRF-520 MOSFET cost about a buck:
    http://www.worldwidedx.com/threads/mosfet-conversions-for-upd858-and-mb8719-boards.95853/

    You will find the C179 cap close to the front/left corner of the main board close to the right of the final/driver transistors and right next to test points 1 & 2.
     
    #12 Robb, Apr 19, 2017
    Last edited: Apr 20, 2017
    LeapFrog likes this.
  13. Klondike Mike

    Klondike Mike
    Expand Collapse
    Well-Known Member

    Joined:
    May 31, 2010
    Messages:
    482
    Likes Received:
    122
  14. Robb

    Robb
    Expand Collapse
    Yup

    Joined:
    Dec 18, 2008
    Messages:
    9,924
    Likes Received:
    1,861
    Mike:
    Do you have tantalum kits too?
     
  15. Klondike Mike

    Klondike Mike
    Expand Collapse
    Well-Known Member

    Joined:
    May 31, 2010
    Messages:
    482
    Likes Received:
    122
    I've been pondering whether to venture in on this. I've got a spool of 2.2's for personal use. Tantalum's are much more costlier than electrolytics. What would you recommend?
     

Share This Page