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IC_765 Power Supply Pin Outs

Discussion in 'Radio Circuits, Repair & Performance' started by NW9R, Aug 29, 2013.

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  1. NW9R

    NW9R Ham Member QRZ Page

    The drop in DC supply or regulator, in the IC-765 has a molex which allows you to detach the drop in AC to DC supply. There are 6 pin outs, two are 12 VDC and two are 12 VDC (Negative). There is also two additional smaller wires in that same molex connector which I assume are also 12 VDC? I cannot locate a schematic to trace that out. Anyone know what those two wires are for? I plan to run a 765 off DC to be cleaner, cooler and lighter weight for the radio overall.

  2. W9GB

    W9GB Ham Member QRZ Page

    INSTRUCTION and SERVICE MANUALS answer 99.9% radio query questions asked here on QRZ.



    The "drop-in supply" is a Switch-Mode Power Supply (SMPS) for DC inside the radio !!!
    READ PAGE 3-12, Paragraph 3-6-1 in Service Manual !!!

    Chris -- Why are you opening up this radio???
    Your question, and justification for why -- tell me you really don't know much about this radio.
    It was NOT designed for what you are suggesting.

    This was one of the last Icom models (1990s) that operated from AC
    with the SMPS DC power supply inside the radio.

    REAR PANEL of Icom IC-765


    Attached Files:

    Last edited: Aug 29, 2013
  3. NW9R

    NW9R Ham Member QRZ Page

    The rear panel has no DC input. I was looking for teh wiring between the regulator and the radio where the regulator unit converts the output to DC and what pins. I believe the four pins on the molex are the ones I need. The other two I think are for switching the AC power on/off, very small wire. The back panel pics provide no info. Its the schematic I will look into.

    THe AC supply generates a lot of heat internally, not to mention within the power supply itself. This is the major cause for the power supplies to fail in this and other similar drop in power supply units.
    The power supply sometimes will generate noise in the rcv signal.
    The power supply adds weight to the radio also.

    The radio can operate off an external DC supply of suitable current capability.
  4. N0SYA

    N0SYA Ham Member QRZ Page

    I opened my 765, removed the hot running and rfi noisy psu and simply plugged another Icom dc power cable to the connector in the 765. Worked fb as the pinout is the same. The extra wires are for ac psu power line on/off far as I know. Conversely, I used the 765 internal psu as an external psu for various rigs every once in a while. Just have to do some hacking to geta ac into it and watch out for the heat sink fins, they're like a porcupine with a razor coat.
  5. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    The rear panel should have two pins connected to a dry set of switch contacts that are a part of the power switch.
    The two small wires on the molex are to be connected to those switch contacts.
    That turns on the power supply by way of a slave relay in the power supply.
    I have one of those supplies for an IC-745/751.
  6. NW9R

    NW9R Ham Member QRZ Page

    THat is what I kinda remember from a long time ago. I agree. The internal supply sometimes, sometimes, is RFI noisy, but mainly, generates a lot of internal cabinet heat...
  7. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    The internal power supply I have is not in my 745 for those reasons.
  8. NW9R

    NW9R Ham Member QRZ Page

    Exactly! One other thing, anyone have any idea about why color paint is on the 765, 761, 751 series? Looks like dark grey, but not black....
  9. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    The case on my 745 is the same as a 751....
    The colors appear to be a two tone green dark green case and much darker green front panel.
  10. N0SYA

    N0SYA Ham Member QRZ Page

    I noticed the 76x paint scheme matched some of the hts (32at) of the era, as well as the 970 v/uhf rig.

    The reason I ventured to do the psu-ectomy is every few weeks at turn on the smeter bulb would blow. After wiring the psu on all the time but using the rig's power switch to power the rig on and off no more lost bulbs at power up. Then I decided hey I gat this nice dc power cable, why not make the psu external?
  11. NW9R

    NW9R Ham Member QRZ Page

    Kinda the color I noted, very subtle "green" almost a greyish hue...really hard to tell...well, will come up with something....

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