Yaesu FT757GX Help Needed!

Discussion in 'General Technical Questions and Answers' started by W2MDM, Nov 11, 2018 at 12:03 AM.

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  1. W2MDM

    W2MDM Ham Member QRZ Page

    I replaced the battery in my Yaesu 757gx as the memories were not holding. This necessitated removing the main top PCB along with the 16 connectors. I screwed up, and cannot remember which plug goes to which receptacle. Some are easy because of the length of the wire and location. However there are a bunch that I cannot re attach. I thought I had it right, but the radio just squealed and did not power up.
    I have the service manual, but it is not clear as to the connections. I might add that all the plugs are numbered, but the receptacles are not all marked and the ones that are don't match.
    Does anyone have any idea of where I can go to solve this? A photo or diagram somewhere? Google was no help.
    Any ideas/directions appreciated!

    Thanks
    Mike
    W2MDM
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I don't, but if you ever have to do something similar again: Colored permanent markers in a wide variety of colors sure helps.

    I always put a "dot" of a unique color on the male and female mating connectors as they are unplugged (one by one) so it's obvious where they go. In a complex rig, this can take every color of the rainbow and then some.

    I have a lot of markers.:)

    There are some Yaesu specialists out there who can probably help.
     
    NH7RO likes this.
  3. WE4E

    WE4E Premium Subscriber QRZ Page

    Not sure specifically about the 757, but in general, the Japanese are very clever about connectors on a PCB. The generally don't use the same size/pin configuration where there could be a chance of confusion. Pay close attention to the number of pins or to index pins, and it should reveal itself. That radio is old enough that the wire bundles should tell you where they want to go.

    If you've done that and it still acts up, check to make sure you aren't shifted over by one pin on a connector.

    Is there a power-up reset button sequence or some way to reset the cpu? Since you replaced the memory battery, you may have scattered it's chickens and it's powering up in an invalid state.
     
    NH7RO likes this.
  4. N3DT

    N3DT Ham Member QRZ Page

    I have a working 757GX. I'd be willing to help, probably easiest by email which is good on my profile. I too replaced that battery but it didn't last long, plus I couldn't find one with tabs.
     
  5. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    Pretty sure I have one of these packed up .
    until somebody can get you a photo of the inside of their rig try these sites

    http://vk3zpf.com/2012/12/yaesu-fc757-battery-replacement.html
    https://pa0fri.home.xs4all.nl/Mods/FT757GX/FT757GX restauration eng.htm

    also google search for Yaesu FT757GX battery replacement theses videos and pictures
    page 34 of the service manual shows where the connectors go. better than nothin

    I'll check here tomorrow and if you havent got it sorted out I'll dig mine out and get some pixs

    this pdf from F4ANN has some good pixs
    hope this helps and your rig didnt get fried
     

    Attached Files:

    NH7RO likes this.
  6. CX3CP

    CX3CP Ham Member QRZ Page

    HI, I hope the photos help you, be careful not to have the MOX activated, otherwise the radio will not turn on.

    upload_2018-11-11_21-59-43.jpeg
    upload_2018-11-11_21-59-56.jpeg
    upload_2018-11-11_22-0-7.jpeg
    upload_2018-11-11_22-0-28.jpeg
    upload_2018-11-11_22-0-39.jpeg
    upload_2018-11-11_22-0-49.jpeg
     
    NH7RO and VE3CGA like this.
  7. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    I'd be rich if I had a dollar for every time that MOX button caught me.
     
  8. W2MDM

    W2MDM Ham Member QRZ Page

  9. W2MDM

    W2MDM Ham Member QRZ Page

    I found where yellow green goes. Radio powers up! Only problem is now the led display is not lighting up. Any ideas?
     
  10. W2MDM

    W2MDM Ham Member QRZ Page

    Thank you everyone who responded! Got it back together and functioning ! The pics were a big help. Found the led connection and repaired same. Battery is now keeping the memories too,
    Much appreciated!
    Mike W2MDM
     
    NH7RO and CX3CP like this.

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