[1000mp] Reduced signal level on receive

[Dan Z]

I hate to ask the obvious, but are you sure the attenuator is not ON?
If not:
Have you compared the RX signal through the RX port vs A/B?

Before you tear into the rig, I'd suggest a processor reset/reboot.
I believe the attenuator or at least its control is in firmware.
I had a strange A/B audio problem in one of my MPs that I would have sworn was a hardware problem but turned out to be fully cured with a hard reset of the processor.
YMMV
GL,
Dan

 
Dan Zeitlin - K2YWE
South Shore ARC - K3AU
Annapolis, Maryland
http://danzee.org


________________________________
 From: Tod Olson <tod at k0to.us>
To: Ft1000MP <1000mp at mailman.qth.net> 
Sent: Saturday, January 18, 2014 1:35 PM
Subject: [1000mp] Reduced signal level on receive
 

I noticed yesterday that there is reduced signal level [not zero signal
level] on RX with one of my FT1000MP¹s. Since I have two identical radios I
compared the signals from the same antennas applied one at a time to each of
the radios. The signal reduction appears to be present on all bands.

My next test will be to inject a known signal level from a signal generator
and verify that the signal reduction is essentially constant across all of
the bands. I expect that test to be positive ‹ essentially constant
reduction of RX signal across all bands.

From the service manual I see that on the input to the BandPass filter board
there is a relay that connects the antenna to the output of the bandpass
filters when transmitting and connects to the RX input circuits when
receiving. In the receive path there is an unusual symbol classified as a
diode but which looks like back-to-back diodes. This item shunts the RX line
to ground. In the parts list it is identified as a Œsurge¹ item. I suspect
that when operating SO2R and at one point not having a Dunestar 600 Bandpass
filter in place, the voltage on the RX line from pickup when the other radio
was transmitting at 1500 watts on a different antenna may have stressed this
³surge diode². 

I wonder if anyone has had experience with this ³surge diode² failing. Is
the part still available from Yaesu? Etc.

Tod, K0TO


______________________________________________________________
1000mp mailing list
Home: http://mailman.qth.net/mailman/listinfo/1000mp
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:1000mp at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html