Yaesu 757GX2 VFO

Discussion in 'Radio Circuits, Repair & Performance' started by KB6QXM, May 2, 2020.

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  1. KB6QXM

    KB6QXM Ham Member QRZ Page

    Last night my VFO dial locked up. The shaft on the VFO is frozen. Does anyone have a scrap 757GX2 willing to sell me the part? Has anyone had this issue and was able to resolve it? My e-mail is active on QRZ.
  2. G4COE

    G4COE Ham Member QRZ Page

    Can ya' not strip it down and do a clean job with a drop of machine oil? I had a Kenwood rig not sure if it was a TS440 or something like that VFO shaft that was well and truly ceased brass bush and aluminium shaft, I couldn't even budge it so the lump hammer came out, first I applied some 3 in 1 lubricant waited a few minutes .... it took three good cracks with it held in a vise, I cleaned the entire lot and applied a drop of oil, luckily I didn't bend the shaft... free as a bird after all that.

    A place in UK where you *might* be able get one should you be unlucky Stateside, try hifi ssb click the Yaesu logo.

    Apply anti-seize or whatever wait a while and ensure it's held secure and hit it straight, the third swipe was with frustration.... either it will or won't kinda thing, after which it only came half out dropping more 3 in 1 on it, turning and pulling did the trick, keep everything straight or you'll probably bend or damage it.

    Last edited: May 2, 2020
  3. KA5IPF

    KA5IPF Ham Member QRZ Page

    Do not use 3-1 oil. It's too thick and will gum up over time. Use sewing machine oil. Stand it up and apply a little bit and let it soak in. Do that several times over a couple of days and it might free up.
  4. W9GB

    W9GB Ham Member QRZ Page

    Robert -

    START with the Yaesu FT-757GX Mark II service Manual (Technical Supplement)
    Courtesy of Fox-Tango International, supporting Yaesu Musen owners for 63 years.

    PROPER DISASSEMBLY : Shown on Page 4.
    A frozen Encoder is common ... with these radios.
    TRY Clif Holland, KA5IPF approach / solution FIRST.
    A majority of the Japanese Solid-State HF Transceivers, beginning in 1980s,
    used ROTARY ENCODERS for the Main Frequency Knob.
    PARTS LIST starts on Page 41

    Yaesu part number: Q9000249 ; Z99-W-09 (M8307009)
    Same part used in the Yaesu FT-840 transceiver
    Replacement part, Yaesu # Q90000649 has also been discontinued.

    Greg Ordy, W8WWV : Notes on Rotary Encoders
    http://www.seed-solutions.com/gregordy/Amateur Radio/Experimentation/IC756 Encoder.htm

    Miles, retired bench tech at AES Milwaukee used the Kenwood W02-1836-15
    WITH a change in wiring. This is COPAL RMS20-250-201-1E rotary encoder
    This model (photo below) WITHOUT the “E” may have shorter shaft length.

    You did not Ask, but here is rest of service information commonly requested.

    Incandescent Lamps (PL1, PL2 on front panel),
    Yaesu part number: Q1000047
    OEM part number: BQ044-32514M

    Color Cap (placed over bulb)
    Yaesu part number: S2000006
    Lamp Fuse
    Yaesu part number: Q1000010
    OEM part number: BQ041-22803A, 8 Volt 100 mA Lamp Fuse Bulb.
    OEM part is discontinued, BUT Bill Patton, WY3A (West Chester, PA) sells a suitable replacement lamp (6.5V, 68mA “grain of wheat” bulb) that are right size (T1).

    Two (2) Bulbs for $8.25 Post Paid, while supplies last.
    Lithium Battery (Page 49)
    BAT2001 Yaesu part number: Q9000248 (BAT2001)
    CR-1/3N-P Lithum Battery
    6.0 volt, 160 mAh, 11.6mm x 10.8mm cylindrical
    This is 1/3 N Battery (Cylindrical) that has SOLDER TABS.

    Some radio amateurs install a 1/3 N battery holder, when replacing.
    Keystone (New Hyde Park, NY) offers Thru-Hole and SMT.
    Digi-Key BC1/3N-C-SM-ND
    Last edited: May 2, 2020
  5. W9GB

    W9GB Ham Member QRZ Page

    Miles, retired bench tech at AES Milwaukee used the Kenwood W02-1836-15
    WITH a change in wiring. This is COPAL RMS20-250-201-1E rotary encoder.

    Digi-Key RMS20-250-201-1 : $46.54 each.
    The wires remain in the same order between the original Kenwood plug and the Yaesu plug.
    The Kenwood plug does not fit in the Yaesu transceiver (different connector).

    The Yaesu plug is wired: Brown, Red, Orange Yellow
    The COPAL / Kenwood plug is wired: Black, White, Brown Red
    Black: Power (0) V
    White: Output “A“
    Brown: Output “B“
    Red: Power (+5) V

    So match-up the COPAL part to your specific radio work.
    F7C17C53-8FF0-4942-97EC-BEF55ACE95D0.jpeg 70558403-B96F-41AF-BCB4-70463F761087.jpeg
    COPAL RMS20-250-201 Encoder, disassembly picture courtesy of Roberto, EB4EQA

    NIDEC/Copal Encoder models (Digi-Key distributor)
    RMS Magnetic Rotary Encoders
    REC/RES Rotary Encoders
    Last edited: May 2, 2020
  6. G4COE

    G4COE Ham Member QRZ Page

    Oooops I've fluffed it.... I said 3 in 1 oil I meant WD40 to undo the seizure sorry, thanks Cliff.

  7. W9GB

    W9GB Ham Member QRZ Page

    Tri-Flow Lubricant is my preferred solution for seized TenTec PTOs,
    BUT I have not tried with frozen Rotary Encoders.
    It is a light viscosity lube, formulated with P.T.F.E

    I use their Pin-Point applicator, only requires 1 or 2 drops.
    Bicycle Shops traditionally carry Tri-Flow. ACE Hardware now carrying product.


    Demonstrate the penetrating power of a lubricant
    Last edited: May 3, 2020
    G4COE likes this.
  8. G4COE

    G4COE Ham Member QRZ Page

    Reminds me of water in TV aerial low loss co-ax. been to a few where the aerial plugs corroded and the waters got in the aerial and found it's way some 30ft down the wire to the plug due to
    capillary action.

    Looks like we didn't need strip em' down after all.

    Good video, thanks


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