TYT TH-7800 - Poor LCD Contrast, Service Manual, Schematic

Discussion in 'Mobile Radio Systems' started by K8ROG, Jan 24, 2017.

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  1. K8ROG

    K8ROG Ham Member QRZ Page

    I have a Tytera TH-7800 dual band mobile. The radio seems to work fine but the contrast of the LCD is pretty poor, particularly when compared to my commercial band Kenwood mobile that is mounted in a console right beside the TYT. Does anyone else have this problem? My dealer says that there isn't a fix, "That's just the way it is". I have tried to contact Tytera but no response.

    Does anyone have access or know where I can buy a service manual or schematic for this radio? From my engineering days, most LCDs have some kind of contrast control, even if it means changing a resistor.

    Thanks,
    Roger
    K8ROG
     
  2. AE5DX

    AE5DX Premium Subscriber QRZ Page

    My TYT-9800 seems to have this issue in bright light, daylight conditions, when the display is pointing at eye level or higher. If you tilt it down some, the display is much easier to see. It's almost as if they designed the darn thing for users who are always looking down at it.
     
  3. W4FBI

    W4FBI Ham Member QRZ Page

    It has been my experience that service manuals are not available for virtually all Chinese Ham radios.
     
  4. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    This brings up an interesting issue—LCD screen adjustments. Very few transceivers have any built-in, software adjusts for their LCD screens, especially contrast adjustments. If there is any contrast adjustment, it is typically inside the transceiver. One I can remember, used a fixed-value resistor. Makes one wonder how they set it at the factory!
     
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    It looks like VLCD is set by 2 resistors.

    upload_2018-4-4_17-28-47.png
     
  6. K3UJ

    K3UJ Ham Member QRZ Page

    Seems to be made for under dash mounting (not that we can do that anymore). I have a RS rig that behaves the same way. Straight on it's a little faded, tilt it down, high contrast.
     
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    I do remember that some displays had a "Tilt" control, For that very reason.
     
  8. WC2F

    WC2F Ham Member QRZ Page

    does anyone have the service manual for the tytera md-9600 dual band mobile? a friend of mine is looking for one so that he that is a tech and fix something with the power, that the swr was high and finals blown or some capacitors, but need service manual....

    Thanks

    miguel k4nbc
     
  9. PD1LOI

    PD1LOI Ham Member QRZ Page

    Here the diagram of the TYT TH-7800
     

    Attached Files:

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