[Hammarlund] Newly aquired HQ-129x
Richard Knoppow
1oldlens1 at ix.netcom.com
Mon Feb 7 08:49:08 EST 2011
-----Original Message-----
>From: William A Kulze <wak9 at cornell.edu>
>Sent: Feb 7, 2011 4:27 AM
>To: Carl <km1h at jeremy.mv.com>, "Hammarlund at mailman.qth.net" <Hammarlund at mailman.qth.net>
>Subject: Re: [Hammarlund] Newly aquired HQ-129x
>
>Thanks, Carl. I did run it quite a bit Friday and Saturday, but have been a little nervous about it because of the caps. At least one of them is a BBOD. There's actually two that look just like the BBOD, but are radial leads, I always pictured them as just axial. I'll probably get the recap kit I've seen online and replace the resistors, too. Someone sent me the SAMS and the Ryder off list. I've always like the Sams, lots of good info.
>
>I've got two other Hammarlunds, an HQ-170 that might have been my dad's (another story on how I came by that, I think he gave it to a friend of his before he retired to FL. I knew his son, who now lives in his dad's house and this was in the garage), and a pre-war Super Pro (SP-210 with LW but no MW, The thicker, 3/16" panel with black wrinkle finish). Learned the hard way on that about the need for re-capping 8-( It needs an audio xfmr.
>
>Even in the condition the 129 is in, after alignment, I am really impressed with how it performs on SSB. With the audio at max and adjusting the sensitivity, the noise level is very low. The radio is a real pleasure to listen to.
>
>Thanks for the reply!
>
>Bill W2NVD
My HQ-129-X appears to have all original capacitors except for couple of obvious replacements. It works very well but has a significant frequency calibration error. I think this may be due to a bad cap but have not had a chance to find it.
My RX has all molded paper caps, green bodies with paper labels, forgot who made them. Not all paper caps were like the Black Beauties, they had some special problems which showed up within a very sort time of manufacture. All BB caps were axial lead caps, in fact no radial lead caps (except can type electrolytics and HV oil caps) were made a the time because they preceded printed circuit boards. I am another believer in "if its ain't broke don't fix it". For the most part caps do not fail by shorting except some tantalum caps and they are not found in old radios. Electrolytic filter caps can short but usually just develop low capacitance and high leakage.
Resistors vary all over the place by manufacturer and circuit conditions. Composition resistors tend to increase in value with time and heat. Some change very substantially, perhaps as much as 50%, some hardly at all. The best of the bunch were the Ohmite ones. They usually have smooth molded cases. IRC resistors have rough cases, meant to radiate heat better. Resistors that run warm are more likely to change value than those that stay cold. Composition resistors can also suffer from cracking. If they don't open up they can be quite intermittant and hard to find. Usually poking at the wiring will find them.
The HQ-129-X is remarkably good, quite stable after a reasonable warm-up and has quite good selectivity due to having three IF stages and a combination of overcoupled and critically coupled transformers. This arrangement makes it hard to align the IF without a sweeper of some sort although it can be done. The adjustments can not just be peaked. The crystal filter has two adjustments, one is a simple peaking adjustment but the other is tricky because it is set for _maximum bandwidth_ when the IF switch is set for maximum crystal bandwidth. It can be set by using a modulated generator with about 2khz modulation frequency. The audio will peak at the right setting. The centering of the phasing control can be adjusted over a narrow range, if needed, by means of a pig-tail capacitor, just a bit of insulated wire, near the phasing cap in the filter can. It should not need adjustment but sometimes other stuff has drifted with time and it does. The noise from the filter when in its narrowest setting should show a definite minimum bandwidth (lack of high frequency noise) with the phasing control centered. The shaft has a flat on it so the knob will automatically be centered.
Hammarlund had the best crystal filter of all, a patented circuit later used by Collins and TMC, among others. Its also found on the famous Super-Pro and SP-600-JX receivers but originated on the HQ-120-X.
A caveat about the local oscillator: its set _below_ the signal frequency on the two highest bands. This is not mentioned in either the HQ-120-X or HQ-129-X books but is in the HQ-140-X manual. There is enough range to get it on the wrong side but neither dial calibration or RF tracking will be right.
Once you get your set aligned I would be interested to know the accuracy of both main dial and bandspread dial. I am told they should be quite accurate but, as stated, mine has an error on both.
There are some puzzles about the HQ-129-X, for one thing, why the odd model number, the preceding radio was the HQ-120-X and the following one the HQ-140-X, so what happened to the HQ-130-X? Another puzzle is the arrangement of the dials, why is the broadcast band at the outer edge and the 30mzh band on the inner edge? For best resolution it should be the other way.
It would also be interesting to know something of the paint history. My receiver has a relatively dark front panel, the receivers in the advertising pictures is much lighter. Mine _may_ have been repainted but all the silk screening looks original so I doubt it. I also have what appears to be the matching Hammarlund speaker, its very close to the cabinet in finish but its slightly darker gray and has a very slight greenish tinge, perhaps just age. It is, BTW, a very good Jensen speaker.
Good luck with your RX, and I rather think that if it performs correctly you should not get into it too far.
Richard Knoppow
WB6KBL
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