[Hammarlund] 455 kHz IF T4 will not peak on HQ-180

[Patrick A. Thompson Sr.]

I had a similar problem with an HQ-170 and the HQ-180 shares many of the 
same parts.  There was evidence of the internal cap inside an IF can 
shorting and burning up a resistor.  The internal caps are wafers of 
mica held together by spring tension.  Over time the compression loosens 
allowing the capacitance to drop too low or the cap can short and take 
the B+ to ground as in my case.

I have never seen the value of a cap internal to an IF can printed on a 
schematic but I know I would have appreciated knowing the value.  You 
can carefully remove the old cap from inside the IF can and then 
reassemble the can minus the old capacitor.  Then add a small variable 
cap externally to adjust until you find a usable value. Then substitute 
a fixed cap or if you are happy with the result leave it alone.

If you have a digital camera I'd take lots of photos so I didn't have to 
trust memory.  A good pencil sketch made with care could work as well.

There is a Japanese gentleman's web site that has photos of his 
restoration of an HQ-170.  The text is Japanese past page one but the 
photos speak pretty well! I tried the Google web page translation but 
the Google translation still needs work.

http://www.noobowsystems.com/restorations/hq-170/hq-170-2.html

good luck!

Pat
wa4tuk



Bob Young wrote:
> To make this quick. I aligned the radio with some help here last week and is 
> much better except for a slight squeal on band 3 and band 4 almost like a 
> BFO you get the idea, and also the antenna control maxed out at either end 
> on those two bands. Also could hear other stations very slightly under 
> louder stations at certain points on some bands (all double conversion 
> bands, under 7.35 mHz).
> 
> I now have it apart and checked the 455 kHz transformers and T4 goes all the 
> way in and is probably not peaking, all others are fine and peak, any ideas?
> 
> Bob Young
> Millbury, Ma
> Hammarlund HQ-180 
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