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Author Topic: HQ 120X  (Read 3113 times)
KD0ACY
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Posts: 91




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« on: June 05, 2012, 01:23:39 AM »

I am trying to resurrect a Hammarlund HQ 120X and have a bad choke. Can any one give me the value of #18 & #20? I am sure they are different, so which one is the greater or lessor? I have three on the desk that show 256 ohms, 480 ohms and 835 ohms. Also, are they the same as a H129X?
Many thanks in advance.
Mike
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W0FM
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Posts: 2053




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« Reply #1 on: June 05, 2012, 09:08:47 AM »

Mike,

It is my understanding that the chokes in the HQ 120X and the HQ 129X were the same, but identifying their values from the schematics is a head scratcher. 

73,
Terry, WØFM
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KD0ACY
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Posts: 91




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« Reply #2 on: June 05, 2012, 05:41:23 PM »

Thank you for the reply, Terry! I have done some research on the HQ 129X and find that the filter #108 is # 18 for the HQ120X and of course # 109 of the HQ129x is # 20 for the HQ120 which is  a 900 ohm at 35 Henrie's while the # 18 would be 270 ohms at 16 Henrie's. I wonder if I have wired these, backwords and wonder if the result is that dramatic. My thinking is, there would be a reduction in performance, however not a  burn out situation. I also wonder if I could use a  900 ohm 5 W resistor to check for other problems, knowing that it will not smooth out the ripple, which could be replaced with the proper filter, later.     
Mike
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KA5N
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Posts: 4380




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« Reply #3 on: June 06, 2012, 04:03:47 AM »

Mike
Joseph Henry was an early scientist and the term "Henry" was named for him and therefore
the plural of Henry is Henrys in honor of the man (never  henries nor Henry's). 
There is much interesting reading about Henry and the many other early scientists that
contributed to electronics and radio.

73 Allen KA5N
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KD0ACY
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Posts: 91




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« Reply #4 on: June 06, 2012, 05:38:49 PM »

Thanks Allen. I will try to get some of the books and stand corrected as to the spelling.
Mike
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KD0ACY
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Posts: 91




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« Reply #5 on: June 11, 2012, 02:27:47 PM »

I wonder why no one has responded to my questions, beyond the improper English usage!
Is hard to believe it is that difficult. 
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KD0FAT
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Posts: 64




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« Reply #6 on: June 12, 2012, 06:58:32 PM »

I have both an HQ-129x, and an HQ-120x on the shelf. After reading the Hammarlund manuals for both models (downloaded from BAMA), I believe that these two models are mostly the same. The '120x has two versions, with different tube lineups after the detector tube. Both models appear to have the same power supply circuit, with two filter chokes of 20 Henries each, and a total of 40 mfd of filter capacitance.   If you download the HQ 120x manual from BAMA and read it through, you will find reference to these filter values.
It is not uncommon for a choke to burn out on these receivers. The filter caps become leaky and draw too much current through the B+ line. Something has to give, and it is usually one of the chokes. Maybe better a choke than the power transformer!  This is a lesson on why we replace filter caps. A 20 mfd cap is pretty cheap these days. Now, where can one buy a new 20 Henry choke? ......73, Al.

BTW, the first choke on my '129x was replaced with a wirewound resistor (before I bought the rcvr)--the old gal works just fine with this mod.
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KD0REQ
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Posts: 859




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« Reply #7 on: June 13, 2012, 04:31:41 PM »

open frame chokes can be had at Mouser.  http://www.mouser.com/Hammond/_/N-1z0zldx?Keyword=filter+choke+20+H&FS=True  depends on the current you draw, but a 100 mA shielded is 38 bucks and a 200 mA open frame is $17.  in stock. Triad is also carried, but I stopped looking when I found the Hammonds were in stock.
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KD0FAT
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« Reply #8 on: June 15, 2012, 05:39:26 PM »

Mike, I don't think that this is rocket science. The manual for the HQ-129x talks about a total of 40 henries of inductance and 30 mfd of capacitance in the HV power supply filter. Back in the 1930's, when the -120x and -129x were designed, filter capacitors were much more costly than they are today. On the other hand, high voltage filter chokes were widely used at that time, unlike today. I would suggest that you replace any questionable filter caps in the PS, and if you can find a choke that is close to 20 henries to replace your burned out one, then do it. I don't think that a 10% or 20% difference in inductance value is going to make much difference. The HQ-120 and -129x receivers are a wonderful example of rugged and effective electronic design. Hammarlund's stuff is worth picking up at any hamfest or junk shop, and bringing back to life. Hammarlund is first class: there is no other way to describe it: if you love Boat Anchors, then by all means, do your best to bring the old Hammarlunds back to life.

73----Al--KD0FAT
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KD0ACY
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Posts: 91




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« Reply #9 on: June 15, 2012, 07:36:50 PM »

Thanks Al! I am using a 800 ohm 5w resistor as temp. until I get on from Mouser. My main concern is if I wired them incorrectly, IE, the 900 ohm to pin 8 of the 5U4 when it should be on pin 1 or the 250 ohm, the same way.
Again thanks to you and all, that have helped.
Mike 
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