[Hammarlund] HQ-180A 60 KHz IF Problem - Suggestions?
Steven Reed
reedsteve59 at gmail.com
Wed Feb 2 17:24:32 EST 2022
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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