[ICOM] 75 PRO III Smoked!

[Stephen Budensiek]

Jay,
   Download the link I gave you while ago.   got to page 98 of 104.
You will see R38, R39, and R40 are in the pa dc feed chain, they're
across L8, so I wonder if it is burnt open also.   They feed L6 to the
Drain leads of Q4 and Q5, the output FETS.   Hope this helps.

73's de Stephen, K0SD

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On Mon, Feb 20, 2012 at 7:21 PM,  <jkolin at optonline.net> wrote:
> I have a late production unit. It has the newer PA Board using MOSFETS as drivers and finals.
>
> 3 Days ago I was checking SWR on a new ant. 2/1. Key down w/100W for about 10 seconds. After a few SWR measurements power dropped to 5 W max. Then I could not go into transmit mode. After about a minute in receive mode, smoke billowed out of the rear panel from the PA compartment.
>
> Removed top covers and found 3 burned SMD resistors. R38, R39 & R40.  4.7 ohm. All 3 are in parallel.
>
> Anyone have problems with this newer PA board? I have not been able to find parts layout drawing that applies to this new PA board.
>
> Thanks for all your thoughts.
>
> Jay....
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