2~Meter Radio Problem

Discussion in 'General Electronics Chat' started by ELECTRONERD, Oct 8, 2009.

  1. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
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    Hey Guys,

    I have a DR-140 Alinco transceiver for 2-meters, and it doesn't seem to be working properly. When I was talking to this other ham, he said I had like a AC hum on my signal. I checked the power supply and it seemed to be working fine, the voltage drop wasn't significant when I transmitted and there was a negligible amount of ripple. I tried another power supply and I still had the hum, so it's definitely the radio. The other ham said it might be my VCO in the radio, but I'm not sure. I opened it up and looked inside and I could see that D11 looked suspicious, the solder tabs looked burnt. I attached some photos so you can tell me what you think! I checked the diode with the "diode test" on my multimeter and it seemed fine. I also checked the resistance both ways and it has a high resistance one way and a low resistance the other way; like it should be. I'm not sure what's wrong.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If you are patient and careful, you might indulge in a bit of recreational soldering. Go to any joint that is not clean and shiny and reheat it with a bit of solder - this is most likely a rig done with the good stuff, so only apply lead/tin to the joints (I won't snitch you out).

    Don't let the solder joints get lots bigger - use wick to pull off excess. You are just trying to insure the connections are all passing electricity.

    I would leave the surface mount components alone.
     
  3. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    Thanks beenthere, I did think of resoldering the joints but I wanted to check with all of you guys first. I'll go ahead and do that now.

    Yeah, I've delt with SMD components before and they are very difficult to solder with! Hopefully one of these days I can make a homeade SMD iron. I've seen several guys do this before.
     
  4. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    I went ahead and resoldered those joints, but apparently it still sounds staticky. Now, the backlight for the LCD display is not working very well either, it seems to have two orange LED's but the one on the left is only working. So it the right side appears to be darkened.
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    A common problem happens if you have a lot of RF floating around. It gets into the mic circuit of the radio itself, or into the external power supply regulator and causes instablility. What sort of antenna are you using? What is the SWR?
     
  6. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    MikeML brings up a good point, but here's a thing...

    Any chance you have a PL (CTCSS) tone turned on? A lot of ham stuff doesn't filter those tones out, could be what the guy is hearing.

    You'd think that, if you are talking thru a repeater, that would be filtered out, but you never know.
     
  7. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    Hi guys,

    Thanks for the responses! I am using a mag-mount antenna that is usually for cars, but I have it on my roof. The last time I checked, the SWR was relatively low. I don't have an antenna tuner or SWR meter at the moment, I might have to get one. As for the CTCSS tone, It isn't necessary on simplex frequencies. I wasn't using a repeater.
     
  8. wr8y

    Active Member

    Sep 16, 2008
    232
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    Understood, but did you have it on by accident? THAT was my point. :cool:
     
  9. tibbles

    Active Member

    Jun 27, 2008
    249
    3
    hi im fairly new to electronics, but a few simple things, could you check for a slightly bulged smoothing or decoupling cap, although this is more likely in the power supply which youve changed,
    are you in proximity to a flourescant or something,
    shielding problem on mic?
    regards dougal
     
  10. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    tibbles,

    A bulging cap wasn't evident anywhere. I wasn't in close proximity to a flourescent lamp, nor was there any sign of EM interference. As for the problem, it would most undoubtly be part of the radio itself.
     
  11. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    Thanks WR8Y for the suggestion, I'll look into that.
     
  12. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    It's easy to turn on by accident, with these menu-driven radios.
     
  13. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    Ok, I guess the problem was this connector I had. When I changed it, it seemed to work fine! Although, only one of the backlight LEDs works, but that's ok. I can still see the LCD display fine, so it isn't a big issue.

    I appreciate all the suggestions guys!
     
  14. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    No problem.

    Where do we send our bill?
     
  15. flat5

    Active Member

    Nov 13, 2008
    403
    17
    Get an SWR meter. They are cheap. You are required to be able to do simply tests on your transmitter. It comes with the license.
     
  16. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    Bill!? What bill?!:eek: :D
     
  17. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    I do have an SWR meter, but that's for HF. I'm thinking of getting a antenna analyzer anyway since you can do the SWR and the impedance of the antenna. I experiment with antennas quite a bit, especially fractal antennas; I just don't have an antenna analyzer to test them with. I've tried the MFJ analyzers, but they say that they aren't very accurate and they only do the amateur bands anyway. For my fractal antennas, I would like to look at the different harmonics of them, which means I'll need a wider frequency range. I can't just have the seperate band designations.
     
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