[Yaesu] FT-897 Won't Turn On...

[KBØNLY]

Got another dead Yaesu, seems like its been a recurring trend lately.  This time it’s a FT-897 and it won’t turn on.  Here is what I know, brand new radio, was installed in a emergency communications center and used maybe once a month.  Then one day they went to turn it on and it wouldn’t turn on.  It was connected to an external Yaesu power supply and only a VHF/UHF dual band antenna, no other connections to it.  It had sat for a month or more with the power supply and radio off.  The power supply turns on and output is a perfect 13.8v and I put a load on it, with a 20a load it drops to 13.72v, power supply seems to be no issue.  I tried the radio on my power supply on the bench as well, no dice.

Took it apart and found that Q1031 on the back of the main board was dead and seems to be a common problem, it’s a 2SJ355, part ordered and replaced, no other components seem to be bad that I can find tracing it out.  Everyone says check R1595 which is on the output of Q1031 and its supposed to be a 6.8 ohm resistor, this radio has a 15 ohm resistor in that position, and its marked as such so its not just out of value.  Not sure why this radio has a different value but I know nobody else ever worked on it.  I checked the voltage regulator that R1595 feeds with some micro clip leads and feeding it 12v I got 5v output so the regulator is ok, its on the back of the board and no way to check it while in the radio and connected.

I have checked all the regulators in the radio, all fine when fed power.  The spots on the main board marked 13.8 all have input voltage on them, no drop over the ribbon cable as some have reported.  The radio still will not power up and I can’t find any other faults.  Any suggestions what I should be looking for now?

73,

Scott KBØNLY