[Hammarlund] HQ-180A 60 KHz IF Problem - Suggestions?

[MICHAEL TALLENT]

I owned a HQ-180AC for many years, just sold it a year ago.  I do remember 
that the 60 Khz alignment in some of the manuals was incorrect.  I don't 
remember all the details but I think it had to do with the switch settings 
when you did the alignment.  I found this out when I did the 60 Khz 
alignment for the first time and when completed it was awful.  I had several 
copies of the manual and I checked another and found a slightly different 
alignment procedure and it work great.  Something to check out.

Mike W6MXV

-----Original Message----- 
From: Steven Reed
Sent: Wednesday, February 02, 2022 10:55 AM
To: Hammarlund at mailman.qth.net
Subject: Re: [Hammarlund] HQ-180A 60 KHz IF Problem - Suggestions?

Thanks for the reply, Bob.  There are no padder caps and judging by the 
soldering work in the IF section, no one has touched it since the radio was 
built.  I have a parts donor that's from around the same timeframe and 
pulled a 60 KHz IF can (they're all the same) to run some measurements.  The 
capacitors are all El Menco dipped micas and measured correct on the LCR 
meter (that's no guarantee of course).  The coil (at least in the one I 
pulled) measured between 3.4 mH at one extreme, to 5.6 mH the other.  This 
puts the "native" resonant frequency of the IF can between 74 KHz and 94 
KHz.  However, Hammarlund's design switches various additional capacitances 
in and out of the circuit by way of the bandwidth and sideband selectors. 
Quite complex.  I've evaluated every capacitor and resistor on the switch 
array and so far have found nothing out of spec.  I also cleaned and checked 
the operation of that switch array under a magnifying glass.

Pulling all six IF transformers and recapping them is something that can 
absolutely be done.  But I'm restraining myself until more is known -- I 
have a hard time digesting the idea that all of those transformers have 
simultaneously drifted.

Steve.

On 2/2/22, 8:36 AM, "Bob kb8tq" <kb8tq at n1k.org> wrote:

    Hi

    A couple “simple” answers to why the drift:

    1) Somebody had a faulty signal generator and re-capped the IF 
transformers.
    If you are lucky, they did it by adding padder caps that are easy to 
remove.

    2) The coils have “tightened up” ( and thus increased in inductance) as 
the radio
    has been through this or that combination of heat / cold / humidity.

    3) The caps have all drifted due to the same sort of issue.

    Yes, there are other possibilities, but the solutions would still fall 
into those three
    categories. The only practical fix (if there aren’t suspicious pad caps) 
is to re-cap
    the transformers.

    Bob

    > On Feb 2, 2022, at 10:28 AM, Steven Reed <reedsteve59 at gmail.com> 
wrote:
    >
    > I’ve been busy restoring a beautiful old HQ-180A.  Previous owners 
have struggled with the IF of this radio and I localized and fixed the major 
smoking gun:  V7’s cathode resistor had drifted from 68 ohms to over 400 
ohms.  I’m now left with the aftermath of all the fiddling and prodding that’s 
happened to the IF section over the years.  The problem I’m now facing is 
that the 60 KHz IF section isn’t resonant at 60 KHz and won’t align 
correctly – I can’t find a peak at 60 KHz in any of the IF transformers (T6 
through T11).  The radio is correctly set according to the manual for this 
procedure.  However, if I vary the signal generator some, the transformers 
will find strong peaks around 54 – 56 KHz.  Been through a lot of steps 
trying to isolate this but keep coming up empty.  The entire 60 KHz IF chain 
appears to be affected – injecting signals further down the line produces 
nothing different.  What would drive the resonant frequency of the ENTIRE 60 
KHz IF chain down like this?
    >
    > 73 – Steve, KW4H
    >
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