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Old 28th Jan 2020, 10:40 pm   #41
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Thanks so much Allan. I very much appreciated your providing some clarity for me about the injection level from the signal generator. Indeed I may very well have it aligned to an image and will go back through it using your parameters.
That is one area that has been a problem for me...too high of an injection level and when confronted with multiple signals as I tune the coils it could very well be that I am grabbing the wrong one.

I checked the 2580 crystal as it was pretty well on frequency at 2580.1 MC so it's not a suspect. I think more-so you have hit on something that is not only quite feasible ("operator error" and aligning to the wrong peak) and skewing the IF in some manner. I'm anxious to give the portable radio trick to check that the lower IFs are 455 above the frequencies and the higher ones are 3035. I'll report back here with an update.
Thanks so much. Your HQ-170 experience in concert with your technical background is so helpful.
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Old 30th Jan 2020, 3:55 am   #42
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Allan, your suggestion about reducing injection levels paid off. By using 10 to 15 microvolts of signal instead of the flame-throwing many times that amount I was able to achieve a decent alignment on all bands (sort of).

But my 2.05 to 4 MC band remains a problem. I can tune the oscillator nicely at
2.1 MC and there is only one signal so I am assuming it is the correct peak.
However I am unable to trim the high end, 4.0 MC. Here's what happens:
With the oscillator tuned to 2.1 MC the tracking produces a correct image on a nearby portable radio at 2.555 MC so I am indeed 455 KC above the desired frequency. Trimmer capacitor C146 has very little effect on the where an injected 4 MC signal appears; it varies it by only a few KCs. If I tune the HQ-180A dial to 4.0 MC and sweep my signal generator across the band it appears that when 4.0 MC is indicated on the dial it is actually receiving 3.600 MC. When checking the tracking the image does appear at 4.055 MC representing that the expected 455 KC IF offset for 3.600 MC. First, I checked C-146 and it measured 1 to 11 pF with a smooth change in capacity with screw rotation, which is good (it's rated at 1-8 pF). Just in case C-146 has something odd going on with itself I temporarily removed it from the circuit and substituted another variable capacitor but it had to change. Clearly my trim capacitor is being prevented from doing what it's supposed to do. I examined the tuning capacitors carefully for bent rotors and stators and found none. Adjustable capacitor C55 measured in excess of its design parameter of 1.5 to 20 pF (1.0 to 24 pF). Although T24, T14 and the top adjustment on T20 went smoothly without any ambiguity I am wondering if somehow one of those could be culpable for a skewed result at 2.1 which maybe throws the work C146 is trying to do off?. Maybe what I think is the 2.1 MC peak isn't although transformer T24 only displayed a single signal peak so maybe I need to examine T14 and T20 more carefully.

Always appreciative of your or anyone else's ideas. Ernie
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Old 30th Jan 2020, 5:39 am   #43
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Another theory popped into my head and this one is almost too simple. As I sat listening to my 4.0 MC signal generator on the HQ-180A while its dial indicated 3.7 MC I got to wondering how much I would need to move the BANDSPREAD knob to land the 4.0 MC signal generator signal at 4.0 on the HQ-180A dial; so I rotated the BANDSPREAD and 4.0 MC was heard at 4.0 MC on the dial when the BANDSPREAD capacitor was fully meshed. They reference the BANDSPREAD throughout the service manual as being at "100" indicated on the dial but when mine is at "100" the BANDSPREAD capacitor is approximately half-meshed. I need to find if there is a reference in any documentation as to what indices are necessary for the BANDSPREAD to be set correctly. If it does, in fact, state that the BANDSPREAD capacitor should be fully meshed at "100" it will give me the proper tracking on the 2.05-4.0 MC band however I then will have to re-adjust all the other bands and hopefully those bands' oscillator transformers and trimmers will accommodate the excursions for moving the HF oscillator and trimmer frequencies where they are supposed to be. If indeed this is necessary it will be apparent to me that someone must have played with the dials and it has never been right since I have owned the receiver.
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Old 30th Jan 2020, 10:18 am   #44
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Default Re: Hammarlund HQ-180A I.F. Help Sought

You seem to have resolved things re that bandspread dial om.
It's not uncommon to find mechanical discrepancies with tuning controls. My current project, the Moreton Cheyney receiver throws up a problem not unlike your bandspread dial. The pointer, which is a wide piece of perspex is free to easily move independently from the tuning mechanism. I guess this is OK when the receiver is in a case but not when the chassis is on the bench.
I suppose your finding could be resolved by arranging a lamp to come on when the bandspread dial is set to 100 (once this corresponds to full mesh!).
You mentioned the small effect of the trimmer capacitor. This is designed to chiefly work at the highest frequency setting of the dial and at that point it can have quite a large effect.
Aligning IF transformers is tricky (almost impossible) without a spectrum analyser or a wobbulator.
You can usually check the end result by feeding in a strong AM test signal and listening to the response as you tune slowly across the signal. Best done with AVC off and an AC voltmeter across the loudspeaker, but with AVC on you can watch the AVC DC voltage as you tune across the signal.
Without a spectrum analyser you could tune the first IF transformer whilst monitoring the grid of the following stage, then move on to the second stage etc. but that is a bit awkward and you need a very high impedance probe with next to no capacitance. Of course, if your receiver has a crystal filter you need to forget about the published IF and instead align around the crystal filter response at its narrowest setting.
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Old 31st Jan 2020, 5:32 am   #45
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Well Allan, my 2.05-4.0 MC woes were apparently not due to the bandspread dial although I still think Hammarlund's mechanical arrangement is odd. (The bandspread only rotates from half-mesh through full mesh to half-mesh instead of full-mesh to unmeshed as most tuning dials' capacitors are set up). Tonight I discovered that there was either component leads touching something they shouldn't or a high resistance solder joint somewhere. Unfortunately I cannot say where it was as I "fixed" the problem by sitting, staring and poking around under the chassis and occasionally touching up what I felt were dubious solder connections. Suddenly 4.0 MC came alive from the signal generator as the receiver sat with its dial set to 4.0 MC. I never have liked "fixing" problems by pure dumb luck...I much prefer knowing what I did. But I've been pounding away at this HQ-180A for the better part of the day and decided I'd quit before I broke something else and turned it off. Tomorrow, when I am more alert I will do the whole alignment runthrough and hopefully whatever I did will hold.
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Old 31st Jan 2020, 11:50 am   #46
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Sounds like a problem or two I had recently om.
There were two problems giving me intermittents on the higher shortwave bands.
One was poor contacts between the tuning condenser rotor and frame plus loose mounting screws. A few sprays of switch cleaner improved matters. Also spraying the wavechange switch helped. I also had a bent plate on the tuner that was used for the higher bands. For some odd reason the designer used two tuning condensers coupled together mechanically.
The HQ180A has metal boxes around the TCs so should be OK re shorting plates, but they rely on regular use to keep the DC resistances of the wipers grounding the rotor low so switch cleaner might help. The same goes for the wavechange switch which relies on regular use to keep the contacts clean.
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Old 3rd Feb 2020, 4:38 pm   #47
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

You are in good company Allan. I have had many challenges that were isolated to loose connections, screws or dirty contacts. For several years I operated an antique radio repair sideline business and of all the radios brought to me with problems probably 1/3 were solved by loose connections, screws or debris/corrosion/dirty wipers or contacts.

Some years back I was restoring a Hallicrafters shortwave receiver and observed that the rotors on the tuning condenser were bent. Oh no! So I dutifully straightened them out only to discover and learn later that the bent sections were to rig the tracking. I had a dickens of a time bending them back to return my tracking to what it should be and to this day I am surprised I didn't fatigue the metal rotor section to the point of breaking it off the condenser. Sheesh!

My HQ-180A does not have the metal or plastic boxes over the two tuning capacitors. It is my understanding that Hammarlund dropped the boxes in the late 1960s. I do wish I had them and have considered homebrewing some just to keep dust out.

Thanks for all your help. I think I am on my way now with this ol' Hammarlund and looking forward to using it a lot.

Ernie
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Old 10th Mar 2020, 2:47 am   #48
agus_h_y
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Just now fixed intermittent problem with my hq180A. If you follow the schematic, V3 and V17 plates are connected to 150 Volt line. What written in voltages table is wrong, suppose to be around 150 volt i don't know either that is old version that uncorrected or mistype.

Now my radio is back to normal.
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