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Author Topic: Adjusting idling current on Icom 746 non pro ?  (Read 231 times)
N4NYY
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Posts: 4742




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« on: September 16, 2009, 06:56:35 PM »

Hi. My Icom 746 non pro TX died. I took it upon myself to repair the unit. The 2SC1972 drivers were shot. I also replaced IC-151 and put in the diode mod.

I then go to align the idling current on the radio according to page 5-4 of the service manual. The very top part, says to connect an ammeter to the supply line, turn R11 fully CCW. Then adjust it to set at 600mA. I am measuring 1.7A in RX, and over 2A in TX. The settings are accoring to the manual. What do you think I am doing wrong?
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KB4QAA
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Posts: 2260




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« Reply #1 on: September 16, 2009, 09:50:01 PM »

after adjusting the trimmer, you are unable to obtain 600ma?
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N1EQ
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Posts: 166


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« Reply #2 on: September 17, 2009, 04:14:52 AM »

Set trim-pots R11, R18, and R204 all to their maximum counter-clockwise positions.

Transmit with no audio on 14.1MHz SSB.

Make note of the current.

Adjust R11 so the current increases 600mA.

Make note of the current.

Adjust R18 so the current increases another 600mA.

Transmit with no audio on 144MHz SSB.

Make note of the current.

Adjust R204 so the current increases 1A.
« Last Edit: January 12, 2010, 08:53:14 AM by N1EQ » Logged
N4NYY
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Posts: 4742




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« Reply #3 on: September 17, 2009, 04:18:31 PM »

N1EQ,

Thanks so much. I did not read the alignment procedure that way.
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N4NYY
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« Reply #4 on: September 18, 2009, 07:31:11 PM »

N1EQ, it went just as you said. Thanks !
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