[R-390] antenna relay troubleshooting (more detail)

[Flowertime01 at wmconnect.com]

Hi Roger, 

Thank you very much. I got this email just as I was getting ready to cry
to the group for more help. I was going to ask about the switch. I have
already replaced the rectifier bridge, CR-102. That did not work so I changed
the antenna relay with no luck. I am ready to go back and do the voltage 
testing you
just prescribed. It figures this would have to turn into a big science 
project.
The good thing is A: It is a good learning experience and B: Thank to nice 
people like you, there is hope :-)

Thanks again, Regards, Scott 
-----------------------------------------------------------

Scott,

Ground the break-in on pin 9 of the TB and operate the break-in switch. This 
should ground the bridge on the AC side. Cause DC to flow on the output side 
of the bridge and operate the antenna relay.

If the break-in relay does not operate that's another problem on it's own 
circuit.

Maybe just exercising the break-in relay contacts a few times will restore 
the circuit operation. If you have not operated the break-in relay in some 
period of time it could just be wanting some exercise to deox a contact face.

If this break-in relay test works you then need to explore from the break-in 
relay contacts in the audio deck to the function switch on the front panel, 
where the function switch grounds the AC side of the bridge to operate the 
antenna relay in CAL. The relay is also operated in standby but we do not worry 
about that mode most of the time. We just listen for the antenna relay click as 
the function switch is changed from AGC to STANDBY or back.

If this test does not work, you need to check for an AC voltage at the diode 
and DC voltage out of the diode.

You got past an open relay coil by replacing the relay (hopefully you did 
check it for continuity) and the bridge.

Now you are for sure likely looking for a wire broken off at one of the 
solder joints around a switch.

The antenna relay circuit goes through the audio module and the power supply 
module. You may need to pull the back shells off the module connectors looking 
for a broken wire. You should also check in the modules for a broken wire at 
a connector or the break-in relay connector. But check the schematic and trace 
the circuit.

A good schematic from any of the web manuals Y2K or TM's should be enough 
document to help you trace and trouble shoot the circuit.

Bad wire in the middle of nowhere in the harness are not a likely problem 
unless some other event has impacted the harness. Then you have a point of 
visible damage and reason to investing for a broken wire in an unlikely place.

Ah science projects. That's part of the disease.

Roger AI4NI
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