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

ab4ab@aol.com ab4ab at aol.com
Mon Feb 14 20:52:23 PST 2011

Finally got to it. Regarding th AF amplifier, indeed, it was the "fuse" 
1/4W 1 ohm resistor open circuit. Looked for the email from the VK 
fellow who had a similar problem and also suggested the "fuse" but 
could not find it to give him the kudos, hopefully he'll read this post 
with thanks to him as well. So I'm back in business, in the mean time 
used an external AF amp as a work around but it's not the same.
Appreciated the suggestion, thanks.
73 de AB4AB

-----Original Message-----
From: Greg D. <ko6th_greg at hotmail.com>
To: ab4ab <ab4ab at aol.com>; amsat-bb <amsat-bb at amsat.org>
Sent: Thu, Sep 9, 2010 3:28 am
Subject: RE: [amsat-bb]  Help needed for my FT-736

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

&gt; To: amsat-bb at amsat.org
&gt; Date: Tue, 31 Aug 2010 18:19:44 -0400
&gt; From: ab4ab at aol.com
&gt; Subject: [amsat-bb]  Help needed for my FT-736
&gt; Hi,
&gt; My FT-736 suddenly lost all audio (apart from the scanning beep). 
&gt; like the Q06 opamp in the AF Unit failed and shorted out the 
&gt; resistor (fuse), 13.8V at the supply side, 2.4V at pin 5. Could 
also be
&gt; that the 2200μF cap. is shot. I can hear low level noise and 
&gt; using an old AF amp. connected to the J02 AF in plug so the rest 
of the
&gt; rig incl. the TX appears fine. Any hints how to cure this sick 
&gt; will be appreciated. Searched for a NEC μPC2002H replacement but 
&gt; joy. Found  a possible solution at:
&gt; http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier
&gt; where the data sheet includes a Single Supply Typical Application
&gt; Circuit, Fig. 3 in the pdf file @:
&gt; Any feedback is welcome, guess Yaesu does not carry any spare 
boards or
&gt; spare parts for this old rig.
&gt; Thanks and 73 de AB4AB
&gt; Ben
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