[Hammarlund] HQ-170A drift

[Jim Wilhite]

Out of curiosity I wonder if some of the components associated with the 
oscillator circuit could have changed value enough to cause this problem? 
Maybe the caps and TC caps in the circuit are now not the value they were 
when the receiver was built.

My recollection of the subject receivers is they were as stable as any other 
receiver of the time after a period of warmup, usually 15-20 minutes.  Some 
things that can cause the  problem is the coil forms expanding as they warm 
even though the filament is on all the time.  Those forms are a cardboard 
type and prone to absorbing moisture over the years, then the heat drives 
the moisture out and problems start.  Also switch contacts can develop some 
corrosion over the year.

There are a lot of potential problems so I wonder if just changing the tube 
fixes the problem, or does it resurface after a while.

Jim
W5JO


-----Original Message----- 


the 6C4 replacement. It has worked on both of my HQ180s. It seems that 
although the 6C4 works well as an oscillator in most rigs, it seems to have 
some problems in the 170s and 180s.