ICOM 751 problems
 

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.

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.

Looks like I have a sick rig. I hope it's simple and doesn't require
unobtainium parts.

Ideas, anyone? I guess I'll tear into it with meter and scope later
today, when I was planning to be using it instead. *sigh*

--
Mike Andrews, W5EGO

Tired old sysadmin

Mike Andrews wrote:
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.

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.

Looks like I have a sick rig. I hope it's simple and doesn't require
unobtainium parts.

Ideas, anyone? I guess I'll tear into it with meter and scope later
today, when I was planning to be using it instead. *sigh*

One further note:

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. Still no XMIT output, though, even though the "XMIT"
LED comes on.

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.

"Through the ICOM 751 with scope and meter" time, I guess. At least I have
the factory schematics, full though they may be of teeny-tiny lettering and
ling, intertwining air-lines with stuff breaking out of them at odd places.
I sure hope the labels on those air-lines are good.

Any -- and I mean _ANY_ -- help, advice, and comments will be very most
welcome.

--
Mike Andrews, W5EGO

Tired old sysadmin

I have the same rig Mike. Have'nt seen exactly your problem, but did
you ever replace your battery backed ram board. I did! I bought
it from Italy guy named Roberto Nardo. The ramboard is battery
backed with a lithium cell. If the battery sinks below a certain
level you have lost your entire operating system. With the one
I bought from Italy you wont loose the entire system if battery
dies, just the 30 memory chnls are lost. You can still carry on
normally from the freqcy dial on whatever freqs you want to use.
Kokomo Joe


************************************************** **
* Ham KH6JF AARS/MARS ABM6JF QCWA WW2 VET WD RADIO *
* Army MARS State Coordinator for Hawaii *
************************************************** **


On Sat, 16 Apr 2005, Mike Andrews wrote:

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.

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.

Looks like I have a sick rig. I hope it's simple and doesn't require
unobtainium parts.

Ideas, anyone? I guess I'll tear into it with meter and scope later
today, when I was planning to be using it instead. *sigh*

--
Mike Andrews, W5EGO

Tired old sysadmin