[ICOM] ICM 751 (non-A) weird bug

[mikea]

My Icom 751 (first model, not a 751A) suddenly developed a problem
this morning: the green "RECEIVE" LED started flashing irregularly,
with the receive audio dropping out when it was off. All controls have
been checked and are in their normal operating positions, squelch pot
is all the way CCW, and this is true in all modes. The "NARROW" LED
comes on for RTTY and CW when I select it, but I have audio only while
the green "RECEIVE" LED is on.

When I crank the RF gain back from its accustomed full-CW (max gain)
position, the "RECEIVE" LED comes back on solid and I get receive audio
again in all modes. 

At first I thought it was just the receive side of the rig. Further
scrutiny shows that while the "XMIT" LED comes on when I transmit,
the dummy load sees nothing from the transmitter and I have no meter
indication with the meter switch in the Ic or Po positions; Vc shows  
good voltage.

I think I just might have a power supply problem, or something in the RX
pulling the PS down to where the TX decides it doesn't want to try, or
maybe something else. The good Vc indication is a bit worrisome.

Anyway, I sure do have a sick rig. I hope it's simple and doesn't require
unobtainium parts. Any -- and I mean _ANY_ -- help, advice, and comments
will be very most welcome.

"Through the ICOM 751 with scope and meter" time, I guess. Good thing I got
double-size copies of the schematics at Kinko's for marking on. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin