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Diagnosing and tracking down sliver mica disease in HQ 170

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Author Topic: Diagnosing and tracking down sliver mica disease in HQ 170  (Read 653 times)
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Posts: 16

« on: October 15, 2018, 03:18:56 PM »

I am asking this community that have experience with the dreaded silver mica disease.  I know the 170 can be affected, but not sure if it affects the 455 KHz, 60 KHz, or other cans in this receiver or that all are prone.  I would be up to replacing or repairing a few, but since it is such a big deal, some guidance on the tracking down part is needed. 

I have experienced some symptoms that appear could be caused by silver mica disease, but not continuously.  The receiver is working very well otherwise, but lacks a re-alignment of the 60KHz IF.  Performance indicates that the alignment may not be warranted.  I use my IC 7600 for comparison and by S meter and audio heard, my HQ 170 is extremely "hot" sensitivity. 

Observations: I do have a suspect tube (V16-6AV6) that has a bad reading on one of three tests done by the tube checker.  Some AVC issues I observe may be caused by this.  Also, some noise occurs sporadically with receiver on standby.  The general noise level on Receive with out an antenna is near zero.  Some episodes of suspect noise increase seem to clear with operation of bandswitch, a symptom acknowledged by Hammarlund at the time but not caused by silver mica disease.

Any additional knowledge on how to diagnose and find a culprit of silver mica disease problem is appreciated.  (Also a source of IF cans). Hi Hi

Bob, NS7H
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« Reply #1 on: October 16, 2018, 02:36:05 PM »

This "disease" effected the 40m input coil on my HQ-180. Just a general lack of signal led me to tracing where I was loosing it. Fortunately I had a carcass of another 180 in the garage and was able to swap out the coil and restore operation pretty easily.
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