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 Post subject: Hammarlund HQ-120-X
PostPosted: Feb Sun 25, 2018 9:54 pm 
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Location: Wood River, Ill.
Hello all,
I recently picked up this receiver at a hamfest and am getting ready to start working on it.

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It came with the original manual with schematic. The problem is that the schematic only indicates the item numbers which translates over to the parts list in the manual. The parts list only refers to a Hammarlund part number, in many cases. Most of the paper/wax caps appear to be original and readable, except in the power supply section. A P.O. has replaced two of the filter caps with a dual 20 mf x 450V. A separate cap was added to the plate supply for the 6V6.
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The current problem is that I believe the 20 mf caps in the power supply filter are too large. Especially for the filter input. I am thinking something more like an 8 or 10 mf cap should be used to keep the B+ at proper levels. Does anyone have a schematic with values added, or at least confirm or deny my thoughts.

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It looks like another cap has exploded at the power switch, as seen in the lower right of the photo. I am just starting in on this, and not really sure what is going on here. It is not shown on the schematic, so quite possibly a modification.

This one is going to take a while, just to figure out what has been changed over the years. But that is part of what this hobby is all about.

Thanks for looking.

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Feb Sun 25, 2018 10:20 pm 
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Chris,

Use either 8 or 10uf for the filter caps. Take a look at the military RBG manual and the followup HQ-129 manual and these may be helpful to you. The RBG was sort of a transition between the original civilian HQ-120 and the later HQ-129.

The HQ-120X manual I have shows most of the component values in the list but not the filter capacitors.

Rodger WQ9E


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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Feb Sun 25, 2018 10:36 pm 
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Thank you very much, Rodger. I will have a look see. Since my posting, I found a restoration thread by K3MSB that is also very helpful. http://www.k3msb.com/hq120/hq120.html

I might add, for anyone that may be following along: This is one of those examples of “do not plug it in until you check it out”! I was told by the seller that the receiver had been “gone thru and recapped”. Definitely not so, in this case! I am always suspicious and always check over before powering up. This thing has not been touched in the last 40 years, or more. Now, I am not complaining, especially considering the price paid. In all fairness to the seller, he did tell me he didn’t know much about it, just what he was told. Personally, I always check out first, and always assume it doesn’t work, when I buy.

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Feb Mon 26, 2018 4:34 pm 
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Hi Chris

I have a diagram of the power supply section on my web site:

http://www.k3msb.com/hq120/hq120.html

About half way down. Search on "Here's a diagram of the filter capacitor / choke section"

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Feb Mon 26, 2018 6:47 pm 
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Those three capacitors in the HQ-129X were all 10 µF. The HQ-129X used the 5U4 (40 µF limit for 1st cap) instead of the 5V4 (32 µF limit for 1st cap).

So 20 µF won't hurt the rectifier, but of course you can use whatever you decide.

Curtis Eickerman

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Feb Mon 26, 2018 7:25 pm 
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Hi Mark,
I found your fine site after I made this posting. I am sure it will be very helpful for this whole restore. Thank you for taking the time to put it together. I am sure it will/has helped others, such as me. My initial problem is that the power supply has already been worked on and possibly modified, so the originals are long gone. My only clue as to the proper size filters was from the chassis layout photo in the original owners manual. All I could see was that at least one of the cap values was a single digit value. Thanks to your site I now know.

Curtis,
Thank you for the reply. I have since found out that the input filter was originally 8mf while the output was 16mf. As I am getting ready to order some caps, I wanted to get the originals, or close, if possible.

Thanks for all the responses.

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Feb Mon 26, 2018 11:40 pm 
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Location: Rochester, NY.
Fairly large chokes (70 Henries is a lot of inductance!) in lieu of large electrolytics was common practice back then. They didn't have the dielectric technology and materials for large capacitances like we do today.
The filter cap values stated in K3MSB's webpage would be the suggested ones.
Nice rig!


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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Thu 01, 2018 7:31 pm 
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Well, I have not made much progress, other than doing a little detective work on the chassis, just to see what is there, what is good and what is bad. I have not ordered the caps yet, either. The original owner’s manual that came with it is nice, and in very good condition, but is not the manual for this receiver. What I have appears to be, what Rider calls a late model receiver. The late model uses the 5V4G rectifier, in lieu of the 5Z4G. It also uses a 6Z7G and 6F8G dual triodes in place of two 6H6 dual diodes in the detector/limiter stages and adding a gain stage. I guess this is a good thing, performance wise. I have not yet tried looking for extra 6Z7 or 6F8’s, as I sure don’t have any of these in my stock of extras.

So far, both chokes, #18 and #20 appear to be good, with resistances “close” to what K3MSB measured. I measured the inductance with my DER EE-5000, and am not quite sure how accurate that is. Checking at 120 hz, I am not very close to what K3MSB measured here. I am not finding any shorts to the core though, checking with an ohm meter. I am just wondering if they can/should be checked with a megger?

The power switch on the AF gain pot is shot, and the band spread dial is broken, while the main dial is severely warped. I ordered the HQ-140 dial set from Radio Daze. The part numbers printed on the dials match, so I am hoping they are the same. Can anyone suggest rivets to attach these to the dial hubs? I found some hollow rivets at Micro Fasteners, but know nothing about them. :?

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Thu 01, 2018 7:59 pm 
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N9whh wrote:
... and the band spread dial is broken, while the main dial is severely warped. I ordered the HQ-140 dial set from Radio Daze. The part numbers printed on the dials match, so I am hoping they are the same. Can anyone suggest rivets to attach these to the dial hubs? I found some hollow rivets at Micro Fasteners, but know nothing about them. :?
Switching out the dials on the 120 for 140 dials is generally a good thing anyway. Then you get a band spread dial that is also marked for 15 Meters which was not present on the 120 dial.

Have you considered just small bolts and nuts for reattaching the dials. I am not sure of the size, but perhaps #0-80 (.06" dia), #2-56 (.086" dia), or #4-40 (.1112" dia) hardware would work. Then if something happens to the dials there is no more need to deal with removing rivets.

Curtis Eickerman

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Fri 02, 2018 3:26 am 
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Thanks Curtis. I have thought about the screws and nuts, as they would be easier and less likely to break or crack the new dials. My concern is for the lack of clearance on the back side. Looks like it may be close on the front side too.

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Sat 03, 2018 7:28 pm 
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I second Curtis' motion for using screws and nuts; a hobby shop should have the short length needed.

I wouldn't worry about high potting the chokes because the failure rate is low for these. If it was stored in a damp area then put the chokes in a hot place (like on a furnace vent) for a few days to bake the moisture out before using but otherwise I wouldn't worry.

Is the power switch completely broken or just making poor contact? If it is at all functional you can use it to switch an AC controlled solid state relay. Control current draw for these relays is so low that even a high resistance contact will still work fine to control them.

Rodger WQ9E


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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Sat 03, 2018 11:14 pm 
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I’ll check into the small screws. I need to put in an order to McMaster Carr, anyway.

The power switch is another matter. Someone connected an 8mf cap across the power switch and chassis ground. The cap had exploded, and the terminal it was connected to was burnt away! Unfortunately the switch is toast.

I have heard the chokes in the 120 are not very robust, particularly #20, thus my concern. They both look good, with no signs of over heating and check out with the ohmmeter, so I will power up on the dim bulb once I get the caps in and see if I can keep the smoke in. The power transformer remains cool with no load, and the AC voltages look reasonable.

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Fri 09, 2018 7:29 pm 
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Hi All,

I found some #2-56 x 1/8” brass binding head screws at McMaster Carr that look like they will work. The binding head screws have the smallest head height of anything that I have found. The dial hub is too thin to consider a flat head screw. I did a trial fit with the dials I have, by removing one rivet, and it looks like I should have enough clearance with the dial stops.

I rebuilt the power supply using some discrete caps until I get a complete 3-section cap from Hayseed. Powering up thru the dim bulb revealed a short in the B+ wiring that was quickly dispatched with some replacement wiring and some heat shrink tubing. Afterwards I let it cook for about an hour while monitoring the voltages, current, and heat.

Last night I gave it a real smoke test and removed the dim bulb and brought it up on the variac. Low and behold the audio came to life with a little hum, and tuned around the RF came to life. I let it play for about 1-1/2 hours, with the transformer and chokes remaining cool to touch.

As I type this, I am thinking about possibly increasing the filter output caps from the stock 20mf to 30 or 40mf. I still need to go thru the rest of the chassis to replace the wax/paper caps and OT resistors. I hope to start this process over the weekend. There is some crumbling rubber insulation to deal with too. Right now I am just happy that it plays! It sounds like I am on my way.

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Sun 11, 2018 4:41 pm 
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Chris,

Looks like you are having fun with the HQ-120x. It has a special place in my heart, as it was the very first piece of amateur equipment I ever touched back about 1964. Since then I have gone through several Hammarlund receivers, but I still have an HQ-120x and it is here to stay. Mine is a little deaf on the higher bands, but I haven't gone through it with the detail that you have. Still, it has good bones and cosmetically it is very nice.

I think you will get a lot of pleasure not only with the restoration, but also with just listening. Good choice.

Marc-k7wxk


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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Thu 15, 2018 2:04 am 
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Hi Marc,

I am having fun with this one. I am still waiting on parts, mostly caps and the AF gain pot. The alignment will be fun too, as I have never done a sweep alignment, but it is all part of the learning experience. My first boat anchor was an HQ-150 that I purchased my first year as a ham, and still have it. This one will be placed in a prominant location as a working unit as one of my favorites. :D

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Thu 15, 2018 4:11 pm 
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Chris,

Coincidently, I also have an HQ-150 and is one of my favorites as well. One that I really like is the HQ-160, which has the same features as the 150, but in the more modern package and dual conversion.

And the list goes on........

Enjoy,
Marc


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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Thu 15, 2018 5:34 pm 
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Location: Morris Plains, N.J. 07950
Keep plugging away at that HQ-120, Chris. They are wonderful receivers, both to work on and to use. It's very easy to fall in love with pre-war Hammarlunds.


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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Mon 19, 2018 6:27 pm 
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Darn it all!!! After going thru the recap and resistor check out my current draw suddenly went up...quite a bit, like double! :oops: When I go thru this process, I always check for operation after each change, just to make sure I haven’t done something stupid. (It is also nice to hear the improvements as I progress thru the chassis.) Well, this time, I had been listening to it for a short time and it was sounding better and much more sensitive than ever. I shut it down to get some lunch, (I don’t leave it running unattended), when I came back...nothing. I did hear/see a snap near one of the filter chokes, and immediately looked at the ammeter and saw it went high, so shut it down. I might add that the recap process was almost complete. All that remains is the BFO area.

I inserted the dim bulb and checked for B+: it was very low, and nonexistent at the second filter choke. The bulb would get bright as the rectifier started to conduct. I immediately isolated that choke and checked it out for continuity and shorts to the core. It looks good, having the same numbers I found to begin with, and no shorts. At this point, it was late in the day, I stopped for the day.

I am thinking a shorted tube, a little wire lead cutoff, or drop of solder someplace. I don’t know, as I have not gone farther, waiting for a fresh look. I do not suspect a misswire, at this point, anyway, as it was playing so nicely for about 15-20 minutes before it all went south, but not necessarily ruling it out. It was a disappointing end to a very productive weekend! :cry:

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Wed 21, 2018 2:24 am 
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Good news: we are back up and running! :D Thanks to my finely tuned trouble shooting skills, (dumb luck!!!),it turned out to be a pinched wire on the B+ buss. The lead going to the send/receive switch got pinched between the choke and the rectifier tube socket. :oops: Something that I didn’t see. Dumb mistake.

All appears good with no apparent damage to anything but my pride. On to finishing the recap and resistor check. I am still waiting on the filter cap from Hayseed, new dials, and AF pot.

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 Post subject: Re: Hammarlund HQ-120-X
PostPosted: Mar Wed 21, 2018 3:27 am 
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Nice work, Chris. You're on the home stretch, and that receiver is worth every bit of attention that you're giving to it.


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