Friday, September 28, 2012

FT-7 repair

As on a previous post stated I have in the shack an Yaesu FT-7 for testing. The radio was not giving audio in the internal speaker but sounded nice on an external unit. I thought problem was with the internal speaker.
Finally got some time to test the internal speaker, it was OK so the problem moved to the external speaker plug.

My initial idea on the problem:

 ....but before starting cleaning the plug switch I had the idea of checking the power cable because audio is also routed there (right of the plug in the schematic).
Found out that pin 1 and 2 were connected on to each other as also 5 and 6...

Red as it was connected, green as it should be connected...
 (image is from FT-7B but is similar to FT-7)
Rewired the plug and guess what.... nice sound coming from the internal unit!

So came to the conclusion, since the radio came with the companion FL-110 amplifier but only one cable, that the power cable initially was for the FL-110. Since both equipments were to be used together I wonder why the folks at Yaesu never tough that this issue could be problematic...

Now there's only one problem with the FT-7, no signal reception on 40m band so the problem is for sure on the band switch or the band oscillator (or a band filter) because rest of the circuit is common to all the other bands that are working good. I don't feel like to check the band switch now so will leave that for another day...

Have a nice day!


glaucous gull said...

Could you e-mail me a circuit diagram as a pdf document please, I need one ugently, not the connection diagram! Brian M6BAQ

Ricardo - CT2GQV said...

Hello Brian,

There's one here:
Hope it helps.