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I need some good video advice ( external video for a Icom 756pro )

Discussion in 'Homebrew and Kit Projects' started by W6VHK, Oct 7, 2016.

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  1. VE3TMT

    VE3TMT Ham Member QRZ Page

    Hi Darrell

    I've already replaced them with other cables that worked just fine.

    24 pin 1mm pitch.

    I'll get as heavy duty as I can.

    My ham friend in Greece received his converter board from China but it was damaged in transit.

  2. VE3TMT

    VE3TMT Ham Member QRZ Page

    Here's basically how I going to do it...


    Line up the two connectors and solder the pins of each back to back, basically making a coupler. Then I can tap the appropriate pins and heat shrink the assembly. Should be pretty easy,

  3. VE3TMT

    VE3TMT Ham Member QRZ Page

    Question for the masses.... I probably know the answer, but honestly I have been looking at ribbon cable pinouts for so long my brain is fried.

    Comparing the pinouts on J891 (MAIN UNIT) against J301 (DISPLAY UNIT) it would appear the pinouts are reversed or at least it looks that way. See attached pinouts.

    The conductors on the ribbon cable that connects the two are on the same side of the cable. So hows does one go from PIN 1 to PIN 1? To me it looks like PIN 1 on one end is PIN 24 on the other.


    When I originally tapped the display board end, I know I tapped the correct spots due to the resistors on each pin. But looking at the two jacks its almost as if the connections do a 180.



    Attached Files:

  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    Yes it does. That may be normal to avoid a twist in the cable. A twist on that type of cable don't work. I think only 1 side makes connection ??.

    The numbering should not mater, As long as you connect to the proper signal.
    Last edited: May 8, 2017
  5. VE3TMT

    VE3TMT Ham Member QRZ Page

    It appears the pins are reversed, 1 is 24, 2 is 23 etc.

    Just has me curious if I was tapping the right spots in the first place.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    Sounds like maybe.

    Are you going by the J891 pinout numbering ?

    If not, That sounds like the problem.
  7. VE3TMT

    VE3TMT Ham Member QRZ Page

    No, I was tapping at the J301 end on the display board.

    But I'm sure I tapped correctly because of the resistors coming off the tap points.
  8. VE3TMT

    VE3TMT Ham Member QRZ Page


    Looking at above, on J891, the red is the 5th pin from the left, green is the 6th and blue is the 7th Hsync is the 8th, and Vsync is 9th from the left. But if you tilt the front panel down, the corresponding pins are on the right side of the cable. At least that is how I interpreted it. According to the board layout, the resistors on each input line (R315, 316, 317, 318, 319) are all on the right end of connector, where the lower arrow is pointing.

    Hence my confusion.

  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    I see the confusion.

    Those PC connections alternate in count with the ribbon cable.

    Those resistors may not be connected to the wire that you think they are.

    I am clueless, Normal. :confused:

    Good Luck, You can figure it out. :)
  10. VE3TMT

    VE3TMT Ham Member QRZ Page

    Here's the schematic for J301. I am 100% sure I tapped the right spot because I confirmed continuity between my tap points and the ends of each corresponding resistor.

    Looking at the back side of the front panel, the top points are on the left side of J301...BUT if I have the panel upside down, that means when it is put back on, the taps are now on the ride side, which would correspond to the outputs of J891. Screen Shot 2017-05-08 at 2.51.24 PM.png

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