[Hammarlund] HQ-150 Question

jthorusen at centcoast.com jthorusen at centcoast.com
Tue Jul 30 23:58:02 EDT 2024 

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.

----- Original Message ----- 
From: "Dan Martin via Hammarlund" <hammarlund at mailman.qth.net>
To: "Richard Knoppow" <dickburk at ix.netcom.com>
Cc: <hammarlund at mailman.qth.net>
Sent: Tuesday, July 30, 2024 10:10
Subject: Re: [Hammarlund] HQ-150 Question


I much appreciate the responses so far.

I have not disassembled and polished the C2 bandspread cap wipers and 
contact disks as I have the main tuning C1 cap assembly. However, the static 
and snapping does not occur when rotating C2, only with C1. I have inspected 
the C2 wipers as closely as can be done without removal and they “look OK”. 
I have wiped them down with IPA and cotton swabs and applied a trace of 
Deoxit. Don’t think C2 is involved. I’ve carefully blown out the C1 cap with 
compressed air and run a business card between all the plates.

For those able and willing, I’ve attached a video with audio of the snapping 
and popping via Dropbox download below. Shown is the LO frequency while 
tuning just above and below 20 mHz on the dial. The HQ-150 has the LO above 
the dial frequency on the bottom four bands and below on the top two bands. 
Make sure your audio is turned up.




--------------------------------------------------------------------------------




Dan WB4GRA

Sent from my iPhone

> On Jul 30, 2024, at 2:19 AM, Richard Knoppow <dickburk at ix.netcom.com> 
> wrote:
>    I was in a bit of a rush before and forgot the arrangement of tuning 
> capacitors for main tuning and band spread. The main tuning cap has two 
> sections, I forgot the details but I think both are used for some bands 
> and the others used individually to give three ranges of capacitance. 
> There are three bandspread sections. It is likely one of these, main or 
> bandspread, is causing the trouble. The usual variable cap problems, 
> rubbing plates or dirt in the cap. If its only one section it may be 
> responsible for the problem on only one band. You may be able to find the 
> problem with a visual inspection. Another way is to run a sheet of typing 
> paper between the plates of the suspected sections. It will either clean 
> out whatever is in there or indicate if  the spacing is wrong due to a 
> bend plate or something of the sort. Canned air may also help.
>   Inspect the sections of the capacitor for spacing. My memory is that all 
> sections of both the main tuning and bandspread cap are on the same shaft. 
> The rotors of both should be centered in the stators. If they are not 
> centered they can cause intermittent shorting problems and will spoil the 
> calibration of the dials. They can be centered by tuning to the low end of 
> any range and adjusting the bearing screws for maximum frequency. The 
> capacitance of a symmetrical air spaced cap will be minimum when its 
> centered. The frequency will go down on either side of the center. 
> However, the problem you describe is more likely to be 3between the plates 
> or a bent plate. If one plate is bent you can probably straighten it with 
> gentle bending with a needle nosed pliers.
>   That's all I have at the moment, I hope its helpful.
>   If the HQ-150 is like its earlier relatives its a very good receiver.
>   BTW, the famous Hammarlund variable crystal filter was introduced on the 
> HQ-120-X (X means it has the crystal).
>   The handbooks on BAMA do not show pictures of the capacitor gangs but 
> there IS a pic in the advertising brochure there. Not exactly high rez but 
> may be of help. This is exactly the same arrangement as used in the 
> HQ-120-X and HQ-129-X so if you can find pix of those it may be of help.
>   The wipers can be cleaned with Deoxit, the ball bearings can be 
> lubricated with light grease, even petroleum jelly (Vaseline) is OK but 
> use the non-medicated kind. Apply with a toothpick.
>
> On 7/29/2024 5:57 PM, Dan Martin via Hammarlund wrote:
>> Have an HQ-150 here with a very noisy high band, 18-31 mHz.  Only the 
>> highest frequency band. No others. Lots of loud pops, snaps, and crackles 
>> while rapidly tuning up and down the band. LO signal on scope shows sharp 
>> variations and spikes in amplitude up and down corresponding to the snaps 
>> and crackles. Noise is main tuning cap movement driven. Radio sits quiet 
>> on a fixed frequency. Try tuning around and it gets real noisy fast.  I 
>> could post a video w/audio if this system could take the bandwidth.
>> I have rotated in several 6C4’s (oscillator) and 6BE6’s (mixer) without 
>> change. I’ve put in place the 6C4 and 6BE6 from my excellent performing 
>> HQ-140, to no avail.  I’ve cleaned, Deoxited, and even used metal polish 
>> to a shiny mirror gleam the C1 cap wipers and contact disks. No change. I’ve 
>> preemptively replaced C89, C6, and C29 caps without change. All 
>> associated resistors in and around osc. grid circuit check OK. Pin 
>> voltages of mixer and osc. OK. I’ve checked and tightened the screws 
>> mounting the cap sub-assembly to the chassis.
>> Have simply run out of ideas and need help and comments.
>> I have worked on HQ-140’s/150’s extensively and currently have one of 
>> each. These are excellent radios and among my very favorites. Treated 
>> right and aligned well the single conversion HQ’s are wonderful.
>> Comments? I’m dead-ended. Need more ideas.
>> Thanks in advance.
>> Dan
>> WB4GRA
>
> -- 
> Richard Knoppow
> Los Angeles
> WB6KBL
> SKCC 19998
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