[Hammarlund] HQ-180A 60 KHz IF Problem - Suggestions?
Bob kb8tq
kb8tq at n1k.org
Wed Feb 2 21:26:53 EST 2022
Hi
Ummm ….. errrr …. 1 ppm at 60 KHz would be 0.06 Hz. 1x10^-8
would be 0.0006 Hz. If the IF is within 6 Hz, that’s overkill. 6 / 60,000 =
1/10,000 = 1x10^-4 …
Your Beckman EPUT meter ( or an LM frequency meter) would be way
more that adequate to be sure things are close.
Bob
> On Feb 2, 2022, at 8:22 PM, jthorusen at centcoast.com wrote:
>
> Hi Steve!
>
> Stop The Presses!!
>
> Before you get into this problem too deeply, I should bring to your
> attention a gotcha that has bitten me before. ...And that is.... can you
> trust your test equipment? Do you have a known good frequency counter (1
> part in 10^8 accuracy) that you can measure your generator with to make sure
> you are putting out 60 KHz and not something else? Have you looked at your
> generator output with a spectrum analyzer to be sure that you are putting
> out a reasonably pure sine wave and not something that has spurs or
> harmonics? Are you using the absolute minimum of injected signal to ensure
> that you are not generating spurious responses due to signal overload?
> Have you isolated the 60 KHz IF strip by pulling the second converter (V5)
> to ensure there are no spurs getting into the 60 KHz IF along with your
> alignment signal?
>
> I don't have an HQ-180, but I do have an HQ-170, and I don't recall any
> particular difficulties aligning it to 60 KHz., although it has been some
> time since I had it on the bench. I could see one or perhaps two tuned
> circuits having problems, but all six, and all with an error in the same
> direction? The probability of that happening is almost vanishingly small.
> I would look for a commonality in all of your measurements and that would
> seem to point to a systematic error, i.e. test equipment or procedure.
>
> Good Luck,
> Jim T.
> KB6GM
> www.centcoast.com
> jthorusen at centcoast.com
>
>
> ----- Original Message -----
> From: "Steven Reed" <reedsteve59 at gmail.com>
> To: <Hammarlund at mailman.qth.net>
> Sent: Wednesday, February 02, 2022 14:24
> Subject: Re: [Hammarlund] HQ-180A 60 KHz IF Problem - Suggestions?
>
>
> Bob, it's not what I wanted to hear, but in all honesty I believe you're
> over the target. In thinking about this some more -- while on one hand it
> is very rare for multiple components to fail, it's probably not so rare for
> multiple components to (as you've pointed out) drift out of spec due to age
> and environmental issues. I think the only rational option at this point is
> to recap everything in that IF section, including the switch. I've got a
> parts HQ-180A as well, in case any of the IF coils have issues. I'll
> probably do the switch first because the work is far less invasive, but if
> that doesn't fix the problem then the transformers come out.
>
> Steve.
>
> On 2/2/22, 2:55 PM, "Bob kb8tq" <kb8tq at n1k.org> wrote:
>
> Hi
>
> Regardless of how you do an alignment (which *can* be tricky. Loading
> resistors / shorting this or that can be involved …) The IF response
> should
> peak in the right vicinity. There should not be some single individual
> component
> that can fail and move all the transformers 20% low. That’s just not how
> this stuff works.
>
> Bob
>
>> On Feb 2, 2022, at 1:57 PM, Steven Reed <reedsteve59 at gmail.com> wrote:
>>
>> THANK YOU! I would love to read through Mr. Lester's method. In my
> 180A, the caps are all the dipped silver micas (El Menco). While not prone
> to failure either, these capacitors have been generally regarded as unlikely
> to fail, even after all these years. In the end I'll probably end up
> replacing them anyway -- but I can't entirely shake the notion that the
> cause of the IF behavior I'm seeing lies elsewhere. Either in something I'm
> doing, the instructions I'm using, or some element -- somewhere in the
> circuitry -- that's gone south and is affecting the entire 60 KHz IF chain.
>>
>> Steve.
>>
>> On 2/2/22, 11:43 AM, "Al Parker" <anchor at ec.rr.com> wrote:
>>
>> Hi all,
>> Hammarlund realized, sometime in the production of the 170/180's,
> that
>> the manual instructions for the 50kc IF were wrong. They didn't do
> a
>> very good job of making that known, but Frank Lester did put out
> the
>> correct method. I have 5 or 6 pages of emails, etc., from that
> period.
>> Right now they are in .jpg's and later today I'll get them into
> a.pdf
>> file and fwd it to anyone interested.
>> Also, as has been mentioned, many of the caps in the IF xfmrs are
>> 'bad'. Many are molded into the base of the xfmrs, and have to be
> dug
>> out with a dremel tool, and replaced with dipped silver micas.
>> I'll get those note on .pdf later this PM, have some other things
>> needing attn b4 then.
>> 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 2/2/2022 12:39 PM, Steven Reed wrote:
>>> Thanks for the reply, Les. I live in southern Arizona and the
> HQ-180A has been sitting below my bench for over a year -- any moisture
> would be long gone by now. On the other hand, it could be REALLY dried out.
> Interesting about the 7036 tubes -- I'll have to look into that. This
> HQ-180A is a keeper and getting good performance out of it is tops on the
> list.
>>>
>>> Steve.
>>>
>>> On 2/2/22, 10:30 AM, "Les Locklear" <leslocklear at hotmail.com> wrote:
>>>
>>> One thing is certain, depending on how or where it was stored.
> The coil forms will soak up moisture. Turn it on and let it burn in for a
> week. A friend had a HQ-180A that he was repairing for a customer that
> wouldn't stop drifting. He actually turned it on and left it alone for a
> month. That solved the problem and it never returned.
>>>
>>> I have an early HQ-180 that the drift is almost not noticeable.
> Only mods are solid stating the PS and some audio mods. A Hayseed cap kit. I
> use 7036 for the Mixer tubes and no longer have to replace 6BE6's. They are
> a taller tube, but computer rated, even better that the mil spec Jan 5750's.
>>>
>>> That might not be the issue you have but it couldn't hurt it to
> let it run for awhile.
>>>
>>> Les
>>>
>>>
>>> ----- Original Message -----
>>> From: Steven Reed <reedsteve59 at gmail.com>
>>> To: <Hammarlund at mailman.qth.net>
>>> Sent: 2/2/2022 11:17:43 AM
>>> Subject: Re: [Hammarlund] HQ-180A 60 KHz IF Problem -
> Suggestions?
>>>
> ________________________________________________________________________________
>>>
>>>
>>> Excellent points, Bob. And it's true that we sometimes get to
> the point with these old boat anchors where you have to stop circling the
> drain and just begin replacing parts. I'm probably at that point -- the
> behavior of the IF section is just too systemic to isolate. I'll replace
> the capacitors on the switch assembly first -- those are much more
> accessible.
>>>
>>> Ran into a logically similar situation with a HRO-60: I finally
> threw in the diagnosis towel and started replacing parts in the affected
> circuit. It got fixed. It's not very elegant of a technique, though.
>>>
>>> Unfortunately, I have no idea what the history of this HQ-180A is
> or how it was stored. It's cosmetically in pretty good shape so I don't
> think it was tossed in the back of a hot barn somewhere. It appears to be a
> later production model, probably built around 1970, so that's a good 52
> years old. 1970 doesn't seem so long ago until you put the math to it!
>>>
>>> Steve.
>>>
>>> On 2/2/22, 9:41 AM, "Bob kb8tq" <kb8tq at n1k.org> wrote:
>>>
>>> Hi
>>>
>>> Coils *do* age. They are a mechanical gizmo and they can / do
> shrink. It
>>> is not surprising that a batch that all came off the coil
> winder on the same
>>> day and all lived in the same environment did pretty much the
> same thing.
>>>
>>> Did the radio get stored out in a shed that routinely got
> *really* hot in the
>>> sun? Did that happen day after day for years? Some radios do
> get stored
>>> that way. You just never quite know ….
>>>
>>> Again, this is only a guess. There is no way to be 100%
> sure …..
>>>
>>> You could spend some “quality time” with a circuit analysis
> program and
>>> maybe work out the original circuit. If you have never done
> that stuff before,
>>> plan on spending more than a bit of time at it …..
>>>
>>> Bob
>>>
>>>> On Feb 2, 2022, at 10:55 AM, Steven Reed <reedsteve59 at gmail.com>
> wrote:
>>>>
>>>> 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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