TS-480 antenna tuner problem

Discussion in 'General Technical Questions and Answers' started by K2TL, Sep 10, 2016.

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  1. K2TL

    K2TL Ham Member QRZ Page

    I inherited a TS-480 that was working perfectly up until today. The radio gets used maybe 1 hour a year as it is not my primary rig. Anyway, it seems that the antenna tuner will not even tune a dummy load on either antenna port. It returns a CW "SWR" error message. I see power out on an external meter but the 480 meter shows no power out even with the tuner switched out. I did a full reset and updated the firmware..no joy. Receive is normal. I found some old posts on the internet from users with a similar problem, but no solutions. Any ideas? Thanks
    1
    Jim K2TL
     
  2. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    The only solution is to open the rig and repair the damaged section of the antenna tuner circuity. Could be a bad or stuck relay, but without opening it up to see what's wrong there's really no way to know.

    What kind of test equipment do you have to check the circuits?
     
    Last edited: Sep 10, 2016
  3. K2TL

    K2TL Ham Member QRZ Page

    Not much, a DVM, L/C meters. I did open it up looking for something obvious on the RF/AT board but no such luck.
     
  4. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    I looked at the service manual.

    Try pulling all the cables around on the final unit board and reconnect them again.

    It may do nothing at all... but if there is a bad connection in one of these cables on the board, this would likely resolve the problem.

    No power output meter reading on the rig display during TX might point us in the right direction on the schematic.
     
    Last edited: Sep 11, 2016
  5. K2TL

    K2TL Ham Member QRZ Page

    I did pull all the cables I could find and reset them..no luck. I might need to get to the under side of the board and look for trouble. I saw on the TS-480 Yahoo group that there was someone with a similar problem who found a cold solder joint on a ribbon cable. Others have had problems with relays. I think the 480 may become an eBay special.
     
  6. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    You could try a soldering iron on the relay terminals. Sometimes the heat will help to release them if they are stuck.

    It's "usually" the relays that are the problem with tuner circuits like this. Of course, i'm sitting in a chair typing this reply on my laptop and am not actually looking at the radio myself. You could try using your DVM in to see if any of the relays are exhibiting any "irregular" readings. One of them might not read like the rest which would help to further isolate the problem.
     
    Last edited: Sep 11, 2016
  7. W8JX

    W8JX Ham Member QRZ Page

    Have you tried simply resetting rigs microprocessor?
     
  8. K2TL

    K2TL Ham Member QRZ Page

    Yes, as I mentioned in my first post, I did a full reset and also reinstalled the latest firmware. The problem is on all bands, so I don't suspect a bandpass relay. The 480 meter does not show power or SWR, although I do have power out into a dummy load and external meter. However, power out is around 80 watts, not the usual 100+, so the rig is folding back a bit for some reason. Receive is normal and sounding good. Thanks for the help.
     
  9. K2TL

    K2TL Ham Member QRZ Page

    I'll poke around the relays again. Can't hurt to try anything.
     
  10. W8JX

    W8JX Ham Member QRZ Page

    Both wattage reading on same meter?
     

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