[Yaesu] Perplexing Problem...

[Jim Hargrave]

Scott,

I'm not familiar with the schematic of the 2400, but here are some
possibilities:

I would check the memory power line going to the CPU. What voltage you are
getting with the radio off? Its possible that the radio power switch is also
switching the backup battery out of the circuit when it is turned on in
order to preserve battery power. If so then you would kill the backup power
when turning off the power supply leaving the backup battery turned off.

Another problem could be a steering diode in the memory power circuit. Most
radios have a diode that provides the memory power which in essence switches
the battery out of the circuit because the source voltage is higher than the
battery voltage. If that diode is shorted, then the external power supply
circuitry could pull the voltage down too far to retain memory.

   * 73's Jim W5IFP *
     w5ifp at gvtc.com




   >-----Original Message-----
   >From: yaesu-bounces at mailman.qth.net
   >[mailto:yaesu-bounces at mailman.qth.net]On Behalf Of KB0NLY
   >Sent: Tuesday, October 13, 2009 7:55 PM
   >To: Yaesu Reflector
   >Subject: [Yaesu] Perplexing Problem...
   >
   >
   >If anyone has been following along here i got a hold of a used
   >FT-2400H that needed a few repairs.  I got the memory battery
   >replaced and it now retains everything when shut off and
   >disconnected from power, i shut it off and shut off the power
   >supply to it yesterday morning and went back down this
   >afternoon and turned it all on and lo and behold it was holding
   >its memory and bandsplit info now.
   >
   >A quick note on the CPU jumpers and bandsplit, never did get
   >that working quite right.  It only works 144-148Mhz on both
   >transmit and receive, its supposed to cover 140-174 on receive,
   >i tried the procedure of holding both the up and down buttons
   >and turning the radio on, had to borrow a mic to do that, and
   >it still stays at 144-148, so oh well i can live with it.
   >
   >The problem is now very perplexing as to whats going on.  I was
   >planning on controlling power to the radio externally via a
   >relay for APRS, adding an ignition sensed and timed relay to it
   >so i don't have to remember to turn the radio on and off, but
   >for some reason this still blanks the radios memory.  Let me explain.
   >
   >Radio turned on, if you shut off the power source to the radio
   >and then turn it back on the radio looses all settings and
   >memories.  It doesn't seem to matter if its a quick off and on
   >or a long off and on, it just looses its memories unless you
   >turn it off with the power button on the radio.
   >
   >As i said, i already replaced the memory battery, checked its
   >voltage, and confirmed that the radio will hold its memory for
   >more than 24 hours without any power source connected, but
   >shutting off the supply voltage to it with the radio on seems
   >to wipe all memories.
   >
   >Any ideas??
   >
   >73,
   >
   >Scott  KB0NLY
   >
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