Yaesu FRG-7700 problem
 

I have had a Yaesu FRG-7700 receiver since about 1982. It's developed a
problem recently in that the frequency shifts all over the map when you
touch the tuning dial. There is no way to tune to a specific frequency
because the tuner and the dial display are so unstable. Anybody have an
idea what may be causing this and how to fix it?

BTW, I haven't changed the backup lithium memory battery since I got the rig
20 years ago -- and all the programmed memories and the clock still work!

Thanks in advance for the help.

Not good and a common problem plauging 7700s as they get older. Usually a
sign that the CPU chip is going bad due to corruption. Usually in the early
stages the radio will finally lock on frequency after 15 to 30 minutes of
warming up and work fine after that, but quits doing this as it gets worse.

Definitely replace the backup battery and hard reset the radio. You might
get very lucky.

"David Trachtenberg" wrote in message
...

Thanks in advance for the help.

It sounds like your synthesizer could be going out of lock. Check the
tuning voltage at the VCO, and you will probably find that it is stuck at
either the low or high end of the rail. Usually, you will find that it is
at the high end. A problem in the reference oscillator could cause this
symptom. If the reference crystal loses activity, this oscillator will drop
out. In order for the synthesizer to lock, you need to have a reference at
that input of the phase detector. Usually, touching the crystal case with a
scope probe will provide enough signal, if the oscillator is working. Very
seldom, is it a chip, although if the clock crystal for the CPU goes
dead..............well, that could also cause those symptoms.

Pete

David wrote in message
...
Ouch. You're the 2nd person who suggested it's probably a bad CPU. Don't
even know who could repair it. Too bad -- it's a great radio. Thanks
anyway.

"truebluefan" wrote in message
s.com...
Not good and a common problem plauging 7700s as they get older. Usually
a
sign that the CPU chip is going bad due to corruption. Usually in the
early
stages the radio will finally lock on frequency after 15 to 30 minutes
of
warming up and work fine after that, but quits doing this as it gets
worse.

Definitely replace the backup battery and hard reset the radio. You
might
get very lucky.

"David Trachtenberg" wrote in message
...

Thanks in advance for the help.