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Author Topic: Icom IC-751 PLL Board vs. IC-761  (Read 241 times)

WA4ZYN

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Icom IC-751 PLL Board vs. IC-761
« on: March 13, 2021, 09:44:29 AM »

Greetings again. Any Icom experts out there?  I am wondering if the PLL board of the Icom IC-751 and IC-751A and IC-761 are identical?  I know they seem identical in "appearance", but am aware that components could be totally different.  Does anyone know the answer to that question?  I am trying to repair the PLL board of my deaf and mute 751, and so far have not been able to get it to do anything (I don't find any RF signals on the PLL board anywhere with RF voltmeter or frequency counter, not even the calibrator "marker" signal). Am wondering about replacing the whole board with one I have found online.  I still need to check voltages on it too.

Thank you for your time and input.
73,
Francis WA4ZYN
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N2AYM

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  • Posts: 375
Re: Icom IC-751 PLL Board vs. IC-761
« Reply #1 on: March 16, 2021, 05:51:41 AM »

Greetings again. Any Icom experts out there?  I am wondering if the PLL board of the Icom IC-751 and IC-751A and IC-761 are identical?  I know they seem identical in "appearance", but am aware that components could be totally different.  Does anyone know the answer to that question?  I am trying to repair the PLL board of my deaf and mute 751, and so far have not been able to get it to do anything (I don't find any RF signals on the PLL board anywhere with RF voltmeter or frequency counter, not even the calibrator "marker" signal). Am wondering about replacing the whole board with one I have found online.  I still need to check voltages on it too.

Thank you for your time and input.
73,

If you download the service manuals for each of these radios you can compare each radios view of the PLL boards.
Francis WA4ZYN
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WA4ZYN

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  • Posts: 327
Re: Icom IC-751 PLL Board vs. IC-761
« Reply #2 on: March 16, 2021, 09:33:19 AM »

Thanks.  I have figured out from that suggestion that the 751 and 751A boards are almost identical (a few resistor/capacitor differences), while the 761 board has a totally-different reference oscillator frequency. 

Thank you!
73,
Francis WA4ZYN
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K7LZR

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Re: Icom IC-751 PLL Board vs. IC-761
« Reply #3 on: June 19, 2022, 07:31:55 AM »

Thanks.  I have figured out from that suggestion that the 751 and 751A boards are almost identical (a few resistor/capacitor differences), while the 761 board has a totally-different reference oscillator frequency. 

Thank you!
73,
Francis WA4ZYN

Not sure if you ever got this fixed or not but a better place to start would be to check for proper operating voltages on the PLL board which you have......
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