TYT TH-9800 Not working correctly.

Discussion in 'Radio Circuits, Repair & Performance' started by G0AOZ, Jul 31, 2019.

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  1. G0AOZ

    G0AOZ Ham Member QRZ Page

    This transceiver has been working satisfactorily for over a year, then the audio on 50 MHz suddenly failed last week. Whilst this is billed as a Quad Band Transceiver, the righthand VFO appears to only cover 144 MHz and 430 MHz. Is that how it should be, or is that another fault? I am specifically wanting to use the 50 MHz band.

    On the lefthand VFO there is no RX or TX audio on 50 MHz or 29 MHz. It transmits a blank carrier on those two bands, but that same VFO works fine on 144 MHz and 430 MHz.

    I have tested it using a power meter and dummy load, used a different PSU, and tried carrying out a full factory reset at least three times.

    Anyone got any suggestions please?
     
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    Do you have the operators manual ? Are you listening using another FM radio when you hear no audio on transmit ?

    upload_2019-7-31_18-38-37.png

    upload_2019-7-31_18-45-16.png
     
  3. G0AOZ

    G0AOZ Ham Member QRZ Page

    Thanks for your reply.

    Yes, I have the operator's manual.

    From what you've stated it looks like the righthand VFO only covers 144 MHz and 430 MHz.

    Yes, I am able to monitor output on another 50 MHz transceiver. All I get is a blank carrier, i.e. no audio. However, with PTT held, pushing any of the microphone buttons produces the relevant DTMF tone on the other transceiver.

    The microphone itself does work when I use 144 MHz or 432 MHz on either VFO.

    I usually use an external speaker, but I notice that the internal speaker no longer works now, on either VFO. I checked after removing the top cover, and the speaker reads 8 ohms on a multimeter.
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Were you using stereo speakers, Where Right and Left VFO come out of separate speakers ?

    Have you adjusted the mic gain in the setup menu ?

    Good Luck. If it can break it can be repaired. :)
     
  5. G0AOZ

    G0AOZ Ham Member QRZ Page

    No, I used a mono external speaker as I assumed from the info on page 11 of the manual that this is what was needed.

    Can you kindly tell me which item in Menu Mode selects mic gain. Can't seem to identify it...

    Having carried out the Factory Reset (F-4 All RESET) several times to no avail, I'm assuming this fault will require a chipset change or something. What do you think...?
     
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    The setting that affects MIC gain is # 34

    Are you pressing SET after you select ALL RESET ?

    Have you check the Remote Head connections ? You can clean them with alcohol.

    Good Luck.
     
  7. G0AOZ

    G0AOZ Ham Member QRZ Page

    Thanks again for your reply.
    Tried adjusting #34. Tried each of WID, MID, NARROW, makes no difference. Still no TX audio on 29 MHz or 50 MHz.
    Yes, I'm pressing SET after selecting F-4 ALL RESET. Takes a few seconds to complete the command, and transceiver then switches right off, then automatically comes back again.
    Checked and cleaned the Remote Head connections (incidentally I'm not using a remote cable). Bear in mind that 144 MHz and 430 MHz both TX ok on lefthand VFO.

    Unfortunately, it looks like this rig is now going to be confined to 144 MHz and 430 MHz use only, unless I can find someone to change one of the chips inside...
     
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

  9. WS4JM

    WS4JM Ham Member QRZ Page

    "I usually use an external speaker, but I notice that the internal speaker no longer works now, on either VFO. I checked after removing the top cover, and the speaker reads 8 ohms on a multimeter."

    Bad speaker jacks are a known issue on this radio. The contacts lose their resilience and will not return to the rest position where the internal speaker is connected. Eventually the external speaker will quit too. I have this issue with mine after about 2 years of mobile use. I tried to get a part number for a replacement jack from TYT but no luck.
     

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