Repairing portable radio, AC works, batt doesn't

Discussion in 'The Projects Forum' started by Hearcostello, May 14, 2016.

  1. Hearcostello

    Thread Starter New Member

    May 14, 2016
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    I have an old small portable radio I'm trying to repair. It runs on 3v, and is supposed to be able to do so from either two D cell batteries, or a 3v AC/DC converter supply.

    The issue:
    It works perfectly with the AC power plugged in.
    It does not work with the batteries.

    I am handy enough w/ a soldering iron and a multi-meter tester.

    I verified that the batteries were installed correctly.

    I have tested the batteries. Both are brand new, each reading around 1.6v, and taped together outside the radio, 3.2v. So power supply is not the issue.

    I have opened the radio and checked the solder points for all wires that connect the battery compartment and terminals to the radio's main circuit board. One was pretty bad (none of them were pretty), so I re-soldered it. The conductivity through that joint is reading fine, but still no power to the radio.

    I even tried plugging a "dummy" jack into the AC supply port, and shorted across its contacts, to try to bypass any sort of switch that might be in that port itself.

    Not that the brand or specs matter, but:
    "Borg Johnson 12Band FM/TV/MW/SW1-9 Receiver HS-912R"

    Yes, I can go buy another one for a couple bucks at a thrift store. Spare me the "duh" comments please ;-)
    I like this one for the TV and shortwave reception. And I wanna try to fix it because I'm not used to getting stumped by such a seemingly simple repair.

    What am I missing?
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    I would say its the dc jack socket thats faulty, most mains/ battery radios switch off the battery positive lead via the mains lead jack socket.


    Post pictures please
     
  3. Hearcostello

    Thread Starter New Member

    May 14, 2016
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    0
    That was my guess too, Dodgydave -- thanks for the reply. Maybe my dummy plug didn't work to prove that wrong or not? Short of cracking that little adaptor jack open, I'm not familiar enough w/ that to know how to test it. Any suggestions?

    What I did:
    I took a variable-voltage AC adaptor plug, the kind w/ a switch on the wall wart for different voltages, and then different plug tips that plug into the cable attached to it. The poles are exposed on the plug tips; I shorted across the two plugs of that tip to try to bypass that switch. Would that not eliminate the switch as a culprit? Though I agree, at this point, it seems the most likely, with everything else working fine...
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    Take the back off and short the socket out.
     
  5. Hearcostello

    Thread Starter New Member

    May 14, 2016
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    0
     
  6. Hearcostello

    Thread Starter New Member

    May 14, 2016
    6
    0
  7. Hearcostello

    Thread Starter New Member

    May 14, 2016
    6
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    Still getting used to the format on this forum. First pic is of the back side of the AC plug socket housing, second photo is the front. I see the two contacts from the back side -- so you're saying just try shorting across those contacts?
     
  8. Hearcostello

    Thread Starter New Member

    May 14, 2016
    6
    0
    Just tried it. Success! Thanks for the help, Dave. I was able to short across two of the three contacts in back and make the battery-only power source connect.

    So... Repairable? Replaceable? If I just hard-wire that switch in the back, I'll need to remember to pull the batteries if I decide to plug in the AC, right?
     
  9. SLK001

    Well-Known Member

    Nov 29, 2011
    820
    229
    Try cleaning the inside contacts of the DC input jack. If that doesn't work, the DC jack can be replaced - you just have to find one, or find another battery operated device that has the same jack and salvage that.
     
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