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.
    Dismiss Notice

Replacing finals

Discussion in 'Amateur Radio Modifications' started by 743SEPA, Nov 22, 2018.

  1. 743SEPA

    743SEPA New Member

    Joined:
    Sep 19, 2018
    Messages:
    44
    Likes Received:
    8
    Is it necessary to have a radio aligned or checked after replacing finals or installing a max mod?


     
    Shadetree Mechanic likes this.

  2. sp5it

    sp5it Master of puppets

    Joined:
    Jul 9, 2009
    Messages:
    971
    Likes Received:
    498
    Depends on radio. in SSB rig bias need to be checked/adjusted.
    For maxmod, nope.
    Mike
     
    Shadetree Mechanic and Robb like this.
  3. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    1,963
    Likes Received:
    1,394
    When a final transistor fails, it tends to short internally. Frequently this causes the 12-Volt DC power on the final transistor's output collector to come shooting out the base terminal, the input side.

    Sometimes parts in the final's input circuit will be damaged. Might only be a 10-ohm resistor that gets scorched, like in a Cobra 29LTD. Or if it's a sideband radio the bias diode, bias trimpot and a resistor or two will all get blown out.

    In some radios, like those made by RCI the modulator transistor can get popped as well. The Max-Mod may require a notch to be ground off the lower-left corner of the Max-Mod's plastic package to clear the anchor lug to the rear from it.

    [​IMG]

    The new final won't work properly until all collateral damage is repaired as well.

    Just replacing the final alone might fix a problem. But only if the final transistor is the only component that got damaged.

    What kind of radio is this? Makes a big difference.

    Installing a MaxMod should not affect any adjustments, if the radio was working normally before the swap.

    73
     
    Shadetree Mechanic likes this.
  4. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

    Joined:
    Aug 25, 2015
    Messages:
    1,136
    Likes Received:
    1,033
    But a side note here and not to hi-jack, the Max-Mod won’t work in a 497HPC. Been there and done that, not as a drop-in replacement. Myself and Key CB shop know this first hand.

    Otherwise, I agree 110% with Nomad. Check supporting components.
     
    Shadetree Mechanic likes this.
  5. 743SEPA

    743SEPA New Member

    Joined:
    Sep 19, 2018
    Messages:
    44
    Likes Received:
    8
    So far I have done the max mod in a 2970 and an AT5555. Easy replacement.
     

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!