[ICOM] 75 PRO III Smoked!

[JK]

Hey Stephen,

Thanks for all your help, suggestions.

I finally was able to get the latest 2007 serv. manual from mods.dk. 
Surprisingly they did not change the photos of the inside of the unit. Still 
showing the old board. They did update the board layout and circuitry to the 
new PA. I found this new PA board is the same one in the IC-7600.

It appears besides the 3 burned resisotrs, one of the finals is shorted to 
ground. I will send it to ICOM in Michigan. They have the best ratings in 
eham.

Thanks again for all,

73,

Jay... NE2Q



----- Original Message ----- 
From: "Stephen Budensiek" <kzerosd at gmail.com>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Tuesday, February 21, 2012 6:53 PM
Subject: Re: [ICOM] 75 PRO III Smoked!


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

*****************************

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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----
Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
Icom Users Net: Sundays, 1700Z, 14.316 MHz
Icom FAQ: http://www.qsl.net/icom/
To support QSL/QTH.net: http://www.qsl.net/donate.html