[Yaesu] ft-757GX keyer unit IC

2002年7月14日 05:47:17 -0700 (PDT)

Hello,
The keyer unit in the FT-757GX has begun a strange
problem. It starts keying by itslef, goes to Transmit
automatically when I insert the key and some other
wierd behaviour in SSB / VOX mode etc.
Upon investigation and comparision with a good keyer
unit board, I confirmed its the keyer unit which is
faulty, resulting in all these problems. Also realized
that the IC Q01 on the keyer unit board F2560000A has
gone bad - The service manual says this chip is TI's
TMS 1751C, but the IC on it has the number M47003. Are
they the same? Anyway, I cannot find more details
about this chip, nor is it available locally.. 
Also realize that Yaesu did some revision on the
board, has couple of tracks cut and few extra
components hand soldered, which are not in the
schematic in the service manual. So the chip change
(if the numbers are not of the same IC) maybe due to
this revision. If the chip Q01 is changed in the
factory design revision, then the chip used is M47003,
also from Texas Instruments.
Any help, suggestions or tips some one can give to
help me get this fixed?
Thanks in advance.
73
Sri, VU2SB
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