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Yaesu FT747GX Repair

Discussion in 'General Technical Questions and Answers' started by VE3YFB, Jan 9, 2018.

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  1. VE3YFB

    VE3YFB XML Subscriber QRZ Page

    I am presently visiting St. Petersburg area and wonder if there are any Hams out there that do repairs to Yaesu FT747GX Transceivers. My problem is that when I tune the digits jump all over the place, I cannot tell what frequency I am actually on. From what I understand this can be caused by malfunction of the Optical Encoder (which I have difficulty finding one) or also told it could be Capacitor problems. Anyone out there can fix this for me. Also maybe someone has an old Yaesu I could get some parts from ? Winston VE3YFB
     
  2. N3DT

    N3DT Ham Member QRZ Page

    Might be easier and even cheaper to find a used 757GXII or similar. Should be able to find one for a few hundred bucks that works. I've got a 757GX that's still working, I thought about selling it, but use it for an alternative rig. It's fine for what it is. Actually I still like it. Just as sensitive as my TS2000 and a lot simpler to work. Works fine with my AL80B too.
     
  3. KM4HGU

    KM4HGU Ham Member QRZ Page

    Clairmont Skyland. (Located in Gainsville GA.) They have repaired both my FT757GX, and my FT757GXII. They do a very good job, and are reasonable.
    There are very few places in this country that will even consider looking at the older SS Yaesu rigs.
     
  4. W9GB

    W9GB Ham Member QRZ Page

    Yaesu FT-747GX Technical Supplement (Service Manual)
    http://w5jgv.com/downloads/FT-747 Technical supplement, A3.pdf

    The Rotary Encoder on tbe Front Panel is mounted to Display Unit Board # C029432AA
    Turn to Service Manual, for details about Display Unit Board.

    Page 12 : Display Unit Parts Layout (component and solder side).
    Page 13 : Schematic Diagram (Shows rotary encoder used is a 3-wire design: CLK, DATA, GND).
    Page 37 : Parts List. S3001, Q9000394, Rotary Code Switch (Rotary Encoder)

    Yaesu FT-747GX Rotary Encoder (S3001)
    You can clearly see this was a mechanical encoder (~24mm square; common size in 1980).
    700FCEA4-1B7E-4C86-BBCF-1B6735497D28.jpeg 75D6E6D4-3447-4A61-A877-4D64F79BE8E7.jpeg

    Repair and Modifications to Yaesu FT-747GX (2010, German web site)
    http://www.elektronikbasteln.pl7.de/ft747gx.html

    Yaesu FT-747GX Rotary Encoder Replacement
    by TA3LKU , November 2017


    CAUTION: There are a Wide Variety of Rotary Encoders, in different sizes and specifications.
    ROTARY ENCODERS 101
    http://trelectronic.com/sites/defau...als/TR_TrainingManual_Rotary_Encoders_101.pdf
    Wikipedia - Rotary Encoders
    https://en.m.wikipedia.org/wiki/Rotary_encoder
     
    Last edited: Jan 28, 2018
  5. W9GB

    W9GB Ham Member QRZ Page

    TRX Bench
    Program #7 : FT-747GX Rotary Encoder Replacement, Part 1


    Program #8 : FT-747GX Rotary Encoder Replacement, Part 2

    ==
    A few Notes, about this video.

    1.) Original Rotary Encoder was mechanical and had Detents. I believe it did NOT have a Push Switch function. In overall size, it is similar to the Bourns EPS series, a Contacting (Mechanical) encoder that is 24mm square.
    http://www.bourns.com/docs/Product-Datasheets/EPS.pdf?sfvrsn=e570520d_2

    2.) TRX Bench Replacement Encoder is Bourns EM14 series : Rotary Optical Encoder w/Switch
    The EM14 series is 14mm square (size) and features Metric and English versions,
    with a variety of shafts (1/4” or 6mm; slotted or flated), PPR, and Detent.
    https://www.mouser.com/ds/2/54/m14-777619.pdf

    Specific Part number used: EM14A0D-24 L064N73
    Mouser web page
    https://www.mouser.com/productdetail/bourns/em14a0d-c24-l064n?qs=sGAEpiMZZMvy8cVzszrmR3d370ceo8WZhQ%2bTiMTrbJU=

    3.) A 3-wire mechanical rotary encoder does NOT require DC voltage source.
    When you switch to Optical, you require a DC source (usually +5 VDC).
    He notes using terminals 1, 2, and GND on new Optical encoder.
    He did not mention where he tapped +5 VDC on the Front Panel PCB.


    4.) Rotary Encoders are Common and Plentiful due to Production/Process industries,
    as well as User Interface for thousands of electronics appliances.
    WATCH the Resolution Specification (stated in PPR, pulses per revolution),
    Critical to matching frequency movement per revolution (processor programmed).

    5.) There are likely Better Replacements, that do not require Drilling knobs for wider shaft diameters. Just a matter a taking time for doing the Parts Research.
    Since 1980, Rotary Encoders have become smaller in size and majority are Metric (6mm) with 1/4” (English) still offered by some models.
     
    Last edited: Jan 28, 2018

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