[ICOM] RE IC 765

[gfiber at comcast.net]

Jim,

As others mentioned check the power supply. But there is more.
If you take off the top cover you will find the internal power supply is connected through a 6 pin DC connector most Icoms use. You can unplug the internal supply and use an external supply to make sure the 765 works normally from a 13.8 VDC 20 amp supply. PLEASE observe the correct polarity and make sure the external DC cable is fused with 20 amp fuses. There are no internal fuses in the 765 for the PA unit. 

If the 765 operates at full power the information below is a most common trouble with the internal supply.

Inside of the power supply there is a flat bar about 1.5 inches long and 1/4 inch wide. Most likely the solder joints are cracked on one or both ends of this bar. The bar is the power supply current shunt so all the current the power supply generates goes through this bar. Its for the current limiting capability of the supply. High current heats the now resistive joints and they open thus causing current starvation.

The fix is not hard. You will need to remove the circuit board from the power supply case. Get the Skill electric screwdriver warmed up as it will see a lot of use. On the bottom of the circuit board you will see the flat bar. Look closely for cracked solder. I suggest you remove the bar, clean up the solder with some solder wick or other de-soldering equipment. Replace the bar, I like to use liquid solder flux when doing this and re-solder it into place. DO NOT solder the length of the bar or go past the two holes drilled into the bar. Doing so will change the resistance of the bar and the current limiting of the power supply. reassemble and reinstall the power supply and give it a try.

I hope this helps.

Gary K8IZ
 -------------- Original message ----------------------
From: "James Bartlett" <jimbartlett at oceanfree.net>
> Hi Guys,
> I am looking for help. A friends '765 has gone faulty.
> It receives ok. The problem is on transmit.
> When keyed in the SSB mode it is ok until talking into the mic, then it shuts 
> down completly. In AM or RTTY mode it shuts down straight away.
> I am wondering if this is a PA or Power Supply problem and am looking for any 
> advice before starting to pull tyhings apart.
> Any help greatly appreciated.
> Thanks in advance
> 
> Jim. Ei2BB
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