ad: AbAuRe-1

YAESU FT-101zd display bug

Discussion in 'Radio Circuits, Repair & Performance' started by OA4BSA, Jan 14, 2012.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-rl
ad: l-BCInc
ad: Left-3
ad: l-gcopper
ad: L-MFJ
ad: abrind-2
ad: Left-2
ad: Subscribe
  1. OA4BSA

    OA4BSA Ham Member QRZ Page

    Hello Everybody,
    I have the following issue, My FT-101zd has the (first) left digit working with an error:
    In the 160, 80 & 40m band actually display number "4", normally this LED never be ON.
    In the 30, 20 & 17m band display number "5", normally should display the number 1 right?
    In the 15, 12 & 10m band display number "6", normally display a "2". I was check the 7805 regulator and brings 4vdc.
    I think could be the main Chip, Please if somebody knows something about this fairlure or ideas,
    All the best, and 73.
    [ OA4BSA ]
  2. W9GB

    W9GB Ham Member QRZ Page

    Ed -

    Yaesu FT-101ZD web page
    Fox Tango - International Yaesu User's Group

    The Yaesu FT-101ZD production runs with serial number: -16 and later
    the OKI MSM9520RS was used as the DISPLAY COUNTER (OH8JEP web page)

    The OKI MSM9520RS was an OEM part and firmware -- this part is no longer available (UNOBTAINIUM).
    Teruhiko Hayashi, JA2SVZ developed a replacement display module that takes advantages of the flexibilities of PIC microcontroller (PIC 16F873)
    to "simulate" the exact functionalities of the original OKI MSM 9520RS used in the DISPLAY COUNTER UNIT:
    PB-2086A, equipped in Yaesu FT-101Z, FT-107, FT-707 and FT-901/902 transceivers.
    This module restores their frequency display functionality when MSM9520RS fails.

    Teruhiko Hayashi (JA2SVZ), e-mail:

    Here is a narrative with photos -- of this repair (New Zealand)

    Fox Tango Manuals for the FT-101ZD series

    Last edited: Jan 15, 2012
  3. KB3PXR

    KB3PXR Ham Member QRZ Page

    Strange fault there, seems like the frequency counter is resetting 40 MHz instead of 0 and counting up from there so when it gets to 10 MHz it is reading 50 MHz and so on.
  4. KO6WB

    KO6WB Premium Subscriber QRZ Page

    It sounds like you have a bit from the chip driving the display decoder set to indicate it is ON. This is the bit that represents the third possible output from the chip. The display operates from a BCD format. This is Binary Coded Decimal. The highest possible bit outputs would be to put out a 1 bit and an 8 bit and the display would decode that as the number 9. You have the 4 bit working incorrectly and as a result the display is always adding 4 to what you should be seeing.
    Check the lines going into the display decoder IC for the digit you are having trouble with. You probably could even remove that bit to make the display proper. There is also the possibility the decoder IC is bad.
    Hope this helps
  5. OA4BSA

    OA4BSA Ham Member QRZ Page

    Thank you very much my friends! with all the information you gave to me I´ll doing many checks tonight,
    hope resolve the problem very soon, if not, I´ll order a new part to replace the display unit.
    73 and many thanks for the time.
  6. KE3WD

    KE3WD Ham Member QRZ Page

    Voltage should be pretty close to exactly 5VDC.

    4V is not right. Either there is something in the circuit that has shorted and is loading down the 7805's output, or the 78-5 has failed and is in need of replacement. Or both.

    I would start by replacing that 7805 and, crossing fingers, fire it up.

Thread Status:
Not open for further replies.

Share This Page

ad: Alphaant-1