[Hammarlund] Dirft Fix/Cure for HQ-170A (VHF) and HQ-180A

[Al Parker]

Hi Chuck,
	Hammarlund issued service notes for the HQ-170 series, which also 
applies to the -180's. <http://www.hammarlund.info/hq178svc.pdf> 
Nothing specifically adresses drift in those notes, but the -170A and 
-180A's had changes which do reduce drift, and are not noted for having 
drift problems.
	Before I continue, let me ask, do you leave your 170A or 180A plugged 
in to a live outlet at all times?  The main differences made in the A 
models was to leave the filaments on at all times for one oscillator and 
it's mixer tube.  That greatly reduced warmup drift.  One other change 
was to replace the HV rectifier tube with silicon diodes.  THis reduced 
one fairly large source of heat inside.  They did not change the power 
transformer when that change was made, so the resulting B+ was a bit higher.
	If you are still having drift problems, I'd try, first wiggling to see 
if that makes changes, then changing oscillator tubes and mixer tubes, 
one at a time, to see what difference you find.  You might also loosen 
and retighten all chassis screws, particularly those with ground lugs, 
including tube sockets.  YOu might put a drop of DeOxit on the sliding 
contacts on the variable capacitor chafts, buth main & bandspread.
	I hope this helps somewhat.
73,
Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 10/21/2010 6:52 PM, Chuck Pool wrote:
> Hi to all Hammarlund fans:
> What reference or information (bulletins) are available that addresses the drift cure/fix for the HQ-170A (VHF) and HQ-180A and all other possible issues?
> Thank you to all.
> Chuck - AA5WG
>
>
>
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