Model Tank..

Discussion in 'The Projects Forum' started by CWA, Aug 3, 2008.

  1. CWA

    Thread Starter New Member

    Aug 3, 2008
    3
    0
    Hey guys, new to the forum - and I'm pretty much an electronics n0Ob..

    Here's the story - I have dug out this old Radio Control Tank (Hobby Engine 1/16 M1A1 Abrams Forest Camo 27Mhz Radio Control Tank) and have been trying to see if it works.

    All seems fine as it used to be except the maximum range (between transmitter and receiver) is terrible (literally about 1m where it used to be up to 25m). I have changed the battery in the controller and this had nothing to do with it, and looking inside it seems that the antenna (or aerial?) wire has come loose. I thought that I could remember which part of the circuit board the antenna went into, and so thought it would just be a case of putting it back into that place and the range would go back to normal.. but this didn't happen.

    Basically I am wondering how I can get the antenna to work again (and therefore increase the range again). If the wire has come out, should soldering it back into the correct place actually make the antenna work again, or is it more complicated than that?

    If doing that SHOULD make it work then I must be trying to put it in the wrong place, and I am stumped as to where the wire should go
    I'm not sure if any of you have any experience with this model, or RC models in general, or whether using pure genius you would be able to tell where the antenna should go (or guess roughly where) just by looking at photos of the circuit diagram.. but I have posted some pics of it in the hope that someone can lol.

    The red arrow shows where I THOUGHT that the antenna wire went, but so far connecting it there has not improved the range at all :confused:

    All help and general advice would be greatly appreciated..

    Cheers,

    CWA :cool:

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  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    With the flash glare and the bad focus, it's really hard to see what's what on the circuit board :(

    Your best bet for taking photos of it would be outside on a cloudy-bright day; the lighting will be very even and there won't be harsh reflections or shadows, and no need to use a flash. You need to be a bit further from the board, too - as blurry photos aren't much of a help either.

    Did you change the length of the antenna wire at all? The total length of the wire is rather critical for good reception; it was made a length that would be resonant to the transmitter frequency.

    Look for a symbol that looks like an upside-down coat hangar, or "ANT" on the board. I couldn't read much of it due to the glare and fuzziness.
     
  3. AllVol

    AAC Fanatic!

    Nov 22, 2005
    55
    2
    Just a guess, but I suspect the antenna wire connects to one of the ports in the white jack in the center of the board. As stated above, it's hard to see in your photos, but judging by the length of wire, plus the obvious "set" it has taken, it would seem the jack with all the other wires is a logical suspect.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    I'll have to disagree with AllVol's assertion that the wire connects to one of the ports in the white jack in the center of the board.

    That jack appears to be the connection for the lighting and motor controls. All of the wires that I can see coming from that jack are pairs twisted together; that would tend to minimize interference. The connector is right next to numerous high-current type transistors.
     
  5. AllVol

    AAC Fanatic!

    Nov 22, 2005
    55
    2
    And you might be right. I wish we could see better, especially the bottom of the board.

    The antenna wire doesn't look like it's been soldered. Tinned, perhaps, but not soldered. I wouldn't leave that much bare wire hanging out, would you? (Photo 2)

    Whoops. I thought there were only two photos. Now there are four.

    To the OP: Your indicated location is duplicated on the other end of the board. Why not there? Neither location shows evidence of being soldered, near as I can tell.

    Just trying to help.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    I couldn't agree with you more there.

    Nope - hard to tell if it's been snipped & stripped, or if it got yanked off of something and the insulation got pulled back.

    I'm sure you are. :)

    Meanwhile, it would be nice to know if there are any markings on the stand-off board labeled "IC2", and what the part number is for IC1.
    IC2 might actually be a plug-in RF module, but it's hard to tell. It could also be a sound effects module, which is actually more likely - I have an effects module that looks somewhat similar.

    Have a look at the attached marked-up photos. I've made aqua-colored arrows pointing at a likely spot. I can't tell what the symbol around the hole is, but it might be an antenna symbol, and it looks like there might be a piece of broken wire coming out there. I just can't tell, the photo isn't clear enough.
    1st photo, arrow is top center; 2nd photo arrow is near top towards the right.
     
  7. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    sgtwookie,

    I suspect that the RF receiver is embodied in the SIP labeled IC2. The DIP device is likely the controller.

    I would normally look near IC2 for the connection to the antenna. It would be helpful to get a glimpse of the area of the board that is at present obscured by the bulk of conductors that presently occult this portion of the printed circuit board.

    I look forward to a photo of superior quality to those thus far provided.

    hgmjr
     
  8. CWA

    Thread Starter New Member

    Aug 3, 2008
    3
    0
    Hey guys, thanks for the responses - but all is good now I found where the antenna goes, soldered it on, and it's working great just as it used to!

    At least next time I know to use a more expensive camera when trying to photograph circuit boards!

    Thanks again for the help,

    CWA :cool:
     
  9. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    It would provide closure for sgtwookie and I if you would post a picture of the board with the antenna installed.

    hgmjr
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Great that you found it - but where on the board was it? :confused:

    Was I even in the ballpark?
     
  11. CWA

    Thread Starter New Member

    Aug 3, 2008
    3
    0
    Basically, I peeled away the big blob of glue that I have labelled in this image, and there was a blob of solder underneath on the base of that green ressistor and i saw "ANT" aswell!

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    (Bottom Right)

    So now its re-soldered to that and it's working fine!

    CWA :cool:
     
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