[amsat-bb] Re: Help needed for my FT-736

[Greg D.]

Hi Ben,

I haven't looked at the schematic, but I'd be much more suspecting that the cap has shorted out than the OpAmp.  Replace it and the "fuse" and see if that doesn't fix things.  If so, you're lucky.  Usually the $$$ parts go first to save the $.000x ones.

Greg  KO6TH


> To: amsat-bb at amsat.org
> Date: Tue, 31 Aug 2010 18:19:44 -0400
> From: ab4ab at aol.com
> Subject: [amsat-bb]  Help needed for my FT-736
> 
> Hi,
> My FT-736 suddenly lost all audio (apart from the scanning beep). Looks 
> like the Q06 opamp in the AF Unit failed and shorted out the 1Ω,1/4W 
> resistor (fuse), 13.8V at the supply side, 2.4V at pin 5. Could also be 
> that the 2200μF cap. is shot. I can hear low level noise and signals 
> using an old AF amp. connected to the J02 AF in plug so the rest of the 
> rig incl. the TX appears fine. Any hints how to cure this sick baby 
> will be appreciated. Searched for a NEC μPC2002H replacement but no 
> joy. Found  a possible solution at:
> http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier
> where the data sheet includes a Single Supply Typical Application 
> Circuit, Fig. 3 in the pdf file @:
> http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/TDA2050-Datasheet.pdf.
> Any feedback is welcome, guess Yaesu does not carry any spare boards or 
> spare parts for this old rig.
> Thanks and 73 de AB4AB
> Ben
> 
> 
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