[Hammarlund] HQ-150 Question

[Dan Martin]

Yes, trying this would be big-boy radio, indeed! Probably not my next choice but I appreciate the suggestion and will file it away.

Checking for shorts and DC continuity among stators and rotors on the big variable caps must be done in close reference to the schematic. For example on the 18-31 mHz band, my snapping-and-popping one, C1E in the oscillator section has the stator at DC ground through L22 - so rotor and stator show as “shorted”, though of course not at RF. 

At any rate, ohmmeter checks on all the rotors and stators show results identical to those on my HQ-140-XA, which is operating perfectly. After these comparative checks and LOTS of cleaning, brushing, air spraying, etc., of the variable caps I’m confident there is no inappropriate blade-to-blade contact going on. Yet the static and popping continues when rotating the tuning knob back and forth across the 18-31 mHz band span.

At this point I’ve gone back to again doing all the same due diligence checks I started over a week ago and I have no new ideas at the moment.

Dan
WB4GRA

Sent from my iPhone

> On Jul 31, 2024, at 1:25 AM, Richard Knoppow <dickburk at ix.netcom.com> wrote:
> 
>    I have never heard of doing this, it seems rather draconian. An ohm meter should serve to find if there are shorts in the cap and I would think running a fairly stiff paint brush through the plates would knock off whiskers, etc.
>    I would be extremely careful of trying this procedure because you might fry something irreplaceable.
> 
>    Clear the swamp???
> 
>> On 7/30/2024 8:58 PM, jthorusen at centcoast.com wrote:
>> Greetings to Dan and the Hammarlund list:
>>    OK, time for nuclear weapons.   Equipment required:   60 watt or larger
>> line isolation transformer.   60 watt dim bulb tester.
>>    Procedure:   Carefully disconnect ALL leads to the C1 tuning capacitor.
>> Double check this step!   Once you are sure that the capacitor has been
>> isolated from all circuitry except chassis ground, connect one output lead
>> of the dim bulb tester to chassis ground.   Connect the other lead to the
>> offending sections of C1.   This places a 60 watt light bulb (for current
>> limiting) in series with the capacitor and an AC line cord.   Plug the AC
>> line cord into the isolation transformer and plug the isolation transformer
>> into the wall.   Rotate the tuning capacitor back and forth through its
>> entire range several times.   Presumably the light bulb will flicker on and
>> off at first, and then will remain off as all "whiskers" or other metallic
>> contaminents are burned away.   Once you can rotate the tuning cap through
>> its entire rangre without any response from the light bulb, un-plug the
>> isolation transformer, disconnect the dim bulb circuit and re-connect all of
>> the normal connections to C1.   Test for noise.
>> Good Luck!
>> Jim T.
>> KB6GM
>> Palus delenda est.
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> SKCC 19998