[Hammarlund] HQ-170A drift

[Bob Camp]

Hi

By the mid to late 60’s you could get radios that were more stable than the 170 / 180 for about the same money. 

From playing with mine, I don’t believe it’s any more or less stable than it was back then. 

What has changed is that a lot of people no longer leave their gear on all the time to take care of warmup and to dry it out.  Moisture / humidify does get into parts and it takes a while to come back out. A radio that’s been out in the shed for a couple of years is going to take a bit longer to stabilize than one that gets used once a day.

Bob

On May 17, 2014, at 9:16 PM, Jim Wilhite <w5jo at brightok.net> wrote:

> 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. 
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