[ICOM] That didn't take long - Re: Icom 706 Dead on Tx and Rx(Again)

[Tim Duffy]

Send it to Icom service in Bellevue, WA ASAP and let them fix it. I think
you will be happy.

73,
Tim K3LR

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Al Waschka
Sent: Saturday, August 03, 2013 9:27 PM
To: ICOM Reflector
Subject: [ICOM] That didn't take long - Re: Icom 706 Dead on Tx and
Rx(Again)

I made three contacts on 20 and it went dead again.  Something really
strange here.  Going to have to get professional help, I guess.  Whatever it
is, must be a bad joint somewhere as it works for a while and then quits. 
Odd thing is, it doesn't get well when the radio cools off.  When it's bad,
it's bad.  Only gets well when the boards are disturbed.


________________________________
From: Al Waschka <awaschka at bellsouth.net>
To: ICOM Reflector <icom at mailman.qth.net> 
Sent: Saturday, August 3, 2013 6:59 PM
Subject: Re: [ICOM] Icom 706 Dead on Tx and Rx (Again)


I'm underwhelmed with the responses (0).  
 
For the record, a close inspection of the main board in the vicinity of the
connector pins for the BPF board appeared to have some solder joints or
splashes that, over time, may have bridged.  I cleaned up everything I saw
and the radio got well (again).  Only time will tell if I fixed it or it
healed itself, only to fail again later.
 
Al
 


________________________________
From: Al Waschka <awaschka at bellsouth.net>
To: ICOM Reflector <icom at mailman.qth.net> 
Sent: Thursday, August 1, 2013 6:55 PM
Subject: [ICOM] Icom 706 Dead on Tx and Rx (Again)


Seveal months ago I posted on here about a problem with my IC-706 (Mk I). 
After finding and replacing a damaged cap, the radio got well and stayed
well for several months, but the problem has now returned.  The replaced cap
is fine.
 
Symptoms are no transmit output and severely degraded (40 dB) receiver
operation on HF.  Based on output Rx noise, the attenuator and preamp appear
to be working fine.  I can hear the noise at three distinct levels depending
on whether the preamp or attenuator are selected.  On strong injected
signals, the relative levels of the three options appear correct.  VHF works
fine.
 
I have instrumented the radio with test points and traced signals through to
the main board.  It appears that the filter unit is working normally. 
Signals injected on all HF bands pass through the filter unit and appear
unattenuated at the input to the main board.  After the receive signal is
routed to the main board from the filter unit, it passes through a high pass
filter consisting of C3, C5, C7 and L4, L5.  The output of this filter does
not look right.  Either some of the diode switching is malfunctioning or
components in the filter have changed values.  Instead of the 3.9 MHz signal
I'm injecting, the filter is passing only high order harmonics, and those at
attenuated levels.
 
Has anyone seen anything like this, and if so, was a cure discovered?  I'll
continued to troubleshoot, but I thought I'd poll the group to see if there
might be a shortcut.
 
Thanks,
 
Al K5TAN 
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To support QSL/QTH.net: http://www.qsl.net/donate.html