[ICOM] 575A Won't Power Up !!

[W8DN]

Greetings All,
  Hopefully someone can add a little light to this problem before I tear
into the rig...

  I have a 575A that will no longer power up. Noticed the problem a few
months ago and the initial symptoms were that the power switch had to be
cycled several times before the rig would turn on. After one particularly
difficult restart attempt, I just left the rig powered up continuously.
Well, last week I turned it off and that was the end of it. I get a little
pop in the speaker and the tx light may flicker but that is it. The rig has
the internal PS so I hooked up to an external power supply but same problem.

  Have not opened the rig up yet but wondering if this is most likely the
obvious - a bad or corroded power switch - or is it likely something else?
Is the switch still available as a repair part?

  Also, I have acquired a 275H and a 475A. Between the three rigs, only one
external keying circuit works. Is it pretty typical for the external keying
circuit to be knocked out? Again, is there a prime suspect.

  Any and all info or suggestions will be appreciated.

Tnx & 73 de Mike / W8DN