Kenwood TR-7800 2M Transceiver display missing segments

Discussion in 'Radio Circuits, Repair & Performance' started by KE0VPA, Feb 18, 2021.

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  1. KE0VPA

    KE0VPA Ham Member QRZ Page

    I picked up a Kenwood TR-7800 at an estate sale. It appears to be fully functional (well it doesn't have a tone card), except the frequency display and channel number displays are displaying numbers with missing segments.

    I can scan up and down and the display changes, but mostly garbage

    The actual 7 segment displays are working, it just isn't getting the correct information between the processor and the display.

    Any have experience with an issue like this? Ideas and where to start?
     
  2. G4COE

    G4COE Ham Member QRZ Page

    The segments that 'are' are missing.... are they continually missing when you tune?

    Dave
     
  3. KE0VPA

    KE0VPA Ham Member QRZ Page

    No they are not continually missing. For example on the channel number display. Channel 1 shows an 8 and channel 2 shows the bottom half of a 2.
     
  4. KA5IPF

    KA5IPF Ham Member QRZ Page

    Look at each number while tuning. If all segments work just not at the right time check the display driver board for cold solder joints. IIRC each has a driver IC.
     
    KE0VPA likes this.
  5. KE0VPA

    KE0VPA Ham Member QRZ Page

    Someone had previously done some repair work to replace one of the resistor packs and it looks like they broke 4 traces. They had repaired them by soldering some small wire whiskers on to the traces. Ended up being a bad solder joint.

    Thanks
     

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