Sunday, May 31, 2015

FT-707 repair (7) External mic

Ok, this time the FT-707 is not the usual suspect.

I started testing transmission since reception looks stable now (more on it on latter posts).
First test showed the the mic ptt was not working, it was "wired to the FT-707" according to the vendor.... let's have a look:

Wrong, it was not wired to the FT-707, all of the wires were badly soldered, with some loose strands and one of the nedeed pins (7) had not even a small mark showing signs of any soldering... oh well...

After rebuilding and some cleaning I notice that it was a litle hard releasing the PTT switch. Let's open the mic to see if it is the release spring worn out or some other issue. After testing I notice the black plastic from the PTT was rubbing a litle against the outer case so I filled inside a little bit..

 ..and now, much better, honestly the MIC in fact has a good internal/electronic design but the mechanical part that's another story. That's poor quality control or the plastics expanded over time which is also likely.

 And after some small cosmetic cleaning here it his:

On to testing the radio again... less than 5w out... this is the first time I tough: it goes for parts... well it was ALC preventing more power, I didn't gave up, and after some tunning it's now "limited" to around 50 during this testing phase, I got easily the, promised by Yaesu, 100w during tests.
Still have to test again in SSB with the mic since I was using CW/AM and only the MIC PTT or MOX.
The other set (the blue color one) it's the same from what I've seen, also I suspect a cap or a transistor will explode shortly since there's some background noise on key down... will see!

Have a nice week!

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