a) No ham band restriction HF 1,8-76MHz, VHF 137-174MHz, UHF 410-470Mhz
b) Only ham bands HF/VHF/UHF + new one 70Mhz.
To do version „a” – remove all SMD or solder joints and leave all 1-6 fields open. After
that, push FAST and LOCK and turn the radio on. Voila!
To do version „b” – leave (if they are shorted) points 1,2and 6, removing all the rest if
any. After that, push FAST and LOCK and turn the radio on. Done.
To remove solder joints it’s good to have smart thing called „SolderWick” or You can
use small tweezers with low power solder iron. BE sure that You disconnected your
solder from mains, before start. As we are working around Memory and uPC is good
to Pay attention to ESD.
After all to avoid any suprises clean the soldering place with Isopropyl Alcohol IPA. It
will ensure that joints are clean and no any solder dust left on place.
You should end with similar result for version „b” mod.
2. Next step will be increasing efficiency of Power Amplifier in our 847 by
applying mod described by Marc PA1O in his superb article about Yaesu
847 filters.
I’m pretty sure few of You experienced already that unlocking gives You advantage to
get into 4m band, but big power supply is a must. It’s mostly due to design of the filters
in PA stage and spurs produced in early stage of TX chain transmitted together with
70Mhz signal. In almost all tested (4 until now) 847 TX current was very high, despite
low TX power and reaches even 17A by 10 W of output ( last tested 847 reached 26A
by 30W of power – really amazing efficiency
)
But better don’t try to transmit for longer period, you can get new # and possibly few
burned elements... and then some troubles with repairing your 847.
