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 Post subject: Hammarlund HX-50 Transmitter
PostPosted: Feb Thu 11, 2021 5:17 am 
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Location: Wood River, Ill.
Hello all,

I recently acquired this HX-50 from an estate sale.
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To be honest, I haven’t really done much of anything to it yet, other than clean the dust out of it. It is really in pretty good condition, and appears to be pretty much in untouched condition. The mic connector appears to have been changed to the Johnson 2-pin offset type. (This works out just fine with me, as it matches the Ranger, so I can use the same mic.)
I do have a problem with the dial cord, though. The large pulley on the geared shaft for the VFO capacitor is a little rusty, and the cord is climbing upon itself and binding. The cord is extremely tight, and can be plucked for a perfect C note. (Hell, I don’t know, I’m no musician!) It’s just very tight. It is tight enough that it is starting to pull one of the idler wheels out of alignment, and the pointer is out of alignment with the dial scale. I am planning on removing it and cleaning up the pulley and shafts. My question is, what is the best line to use for dial lines? I have been using braided nylon fishing line for years on most of the old BC radios that I have been working on. But nylon stretches, and the Hammarlund manual recommends braided Dacron (polyethylene) line. It measures about .025” diameter. Most of what I am finding is braided Dacron fishing line, but when I check them out, they seem to have some kind of wax applied to them. I am concerned that this might be a problem, especially when winding around the small tuning shaft. It has already given me some problems with the line binding on the shaft. Although cleaning it did help, a little.
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This picture was taken before dusting out the chassis. As you can see it does need a good cleaning ! :shock:
Thanks for looking.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Thu 11, 2021 6:19 am 
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I’ll be following your efforts, Chris, as I have one here that I may have to check out/rebuild before I find it a new home. Not many folks want to work on these old beauties any more.

Sure make a pretty pair though,

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Thu 11, 2021 7:18 am 
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Hi Chris, congratulations on getting yet another Cool toy.

The HX-50's are decent transmitters. I've had 3 over the years and the one I have now is an "A" with 160 Meter coils.

The dished tuning shaft profile must be polished smooth for the tuning mechanism to work properly. If that area is rusted or tarnished it supplies too much friction and does what you are seeing happen. In normal operation, the dial string should climb the radius at either end of the recessed area somewhat, but, because of the tension on the string, it should be continually sliding back down into the groove as you continue to turn the knob.

The spring is the termination of one end of the dial string assembly, and is secured by a tab on the tuning cap pulley. If you don't have the manual, you should take a couple pics before, and as you "unwind" the cord. Use some long nose pliers to unhook it and proceed to undo the routing so the tuning knob shaft, and the string's depression drive area are easily accessible. If possible, remove the shaft and mount in a drill motor, then pinch the recess area with some fine steel wool, and spin the shaft with the drill motor. Within a very short time you should be able to finely polish the entire area.

Re assemble everything, and it should work like new.
=====
Hi Chuck, you should get that transmitter on the air, they are a bit difficult to work on in the band switching area but they are fairly open otherwise. I think you would enjoy the transmitter as they are easily tuned and the dials are pretty accurate. No big output on AM, but enough to be a lot of fun.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Fri 12, 2021 4:58 am 
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Well, I’m into it now! :lol: I pulled the front face and removed both the tuning shaft line and the dial line and all related components, including the VFO variable cap. The ultrasonic cleaner and a little Simple Green and warm water made short work of the metal parts, which are now like new and bright and shiny. The cords look to be in good shape, so I will try to reuse. Mike, I will polish up the tuning shaft as you recommend. (I do have the manual plus the Hammarlund factory upgrade sheets, thanks to Rodger.) I plan to restore back to original condition first, before attempting any mods. (I am not usually a proponent of mods, mostly because I don’t think I am qualified for such changes. We will see how it goes.)

I’ll have to admit, that I was not real keen on this transmitter to begin with, but the price was right, and it is somewhat unusual. Besides, it’s starting to grow on me. I do have a nice HQ-180 to go with it, so what the heck... :roll:

Thanks, Mike, for the great advice, as usual! Chuck, I’ll try to keep you all up to date, and hopefully you all can prevent me from doing something stupid. :D

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Sun 14, 2021 4:00 am 
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What else you going to do when the day starts out at 10 deg, F? Well I started out by cleaning and polishing the top side of the chassis. It's far from perfect, but I got most of the spots out of the plated steel finish with Scrubbing Bubbles some Semi Chrome metal polish. My fingers hurt, but the job is done. I cleaned the VFO tuning cap in the ultrasonic cleaner a couple of nights ago, and applied some light oil to the pinion shaft and some synthetic grease to the capacitor bearings. Turns smooth as glass now. It is interesting to note that the bearing balls appear to be nylon or glass. The brass gears cleaned up to like new with just the Simple Green and water in the US cleaner.
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One thing can be said about learning by repetition. I re-attached the VFO capacitor and bracket to the chassis, and started restringing the tuning shaft cord, completing the install. Then learned that the wiring harness that runs across the front of the chassis, needs to be placed behind the vertical portion of the bracket! :oops: It all had to be removed, after spending about an hour or more installing it all. So I removed it and took a walk. (Got in my 10k steps for the day. :D )

After fixing dinner, I retreated back to the dungeon to repeat the work I did this afternoon. :P It took much less time, this time, and I repositioned the harness where it needs to be. (Just a word of caution for anyone that may be considering the same operation.) I proceeded with the mounting of the dial back face and dial tuning cord. It was much easier than I expected. It tunes so much easier now!
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I polished out the brass tuning shaft, as Mike recommended, first. I also cleaned up the large tuning wheel that the cords wrap around. I removed all the rust and rough surface with fine steel wool. I wanted the cords to seek their own track on the wheels, so applied a little Butcher's Bowling Alley wax to the wheels and allowed to dry before polishing it out. So far so good, as it is doing the job.
Attachment:
HX-50-VFO.jpg
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I have not yet applied power. I ordered new filter caps this week, and think I will wait until I get those installed before I try anything like that. The power transformer looks to be in pristine condition, and I don't want to risk damaging it or the solid state rectifiers.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Sun 14, 2021 1:53 pm 
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What a difference!! That really looks nice, well done.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Sun 14, 2021 3:08 pm 
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Nicely done, Chris!

It makes my fingers hurt just looking at it, as I know how much work it takes.
My hands usually make me give up long before it looks as good as yours does.

That HX-50 will be better than new when you’re done.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Fri 19, 2021 7:34 pm 
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Thank You Mike & Chuck! To be honest, it has been almost a week, and my hands are still a little sore, but I got the worst of the work out of the way. Now on to the fun stuff. I pulled the high voltage cage and gave it all a little more thorough cleaning. I found that the anode lead to the PA was loose. There was a cold solder joint where it attaches to the coil. I took care of that. That might have been interesting on first power up.

I cleaned up and put a coat of auto wax on the front panel. It all cleaned up pretty well. I have yet to polish up the knobs.

I am still waiting on filter caps, but I could not resist applying power. I brought it up on the variac slowly, and watched and monitored the whole time. I saw no temperature rises that would be alarming. After a suitable time, I did notice that the 6C10 oscillator is functioning enough that I could pick it up by loose coupling the spectrum analyzer to the tube. I could also spot the frequency change when changing over from USB to LSB, so I guess at least that part is working. It was at this point, that I figured that I had pushed my luck far enough, and shut it all down.

I will spend much of the weekend replacing the electrolytic caps, with caps from my stock. It least I'll be doing something. Another cold weekend in Southern Illinois, but at least it's not as bad as last weekend.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Sun 21, 2021 11:58 pm 
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I have made some progress, this weekend.
Attachment:
HX-50 FRT2.jpg
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I am still waiting on the new filter caps to arrive, but did go in and start replacing the electrolytic caps under the chassis. Curiosity got the best of me, and I checked each one on the Telohmike. Only one of the caps was found to be leaky, but I replaced them just the same. There are still a few film caps under the chassis, but I believe they are not of wax paper construction.

When attempting to tune up the HX-50 on 80m, I could not get any PA cathode current. This prompted a weekend of trouble shooting to find out where the problem was. I was only operating it for short periods of time, because my filter caps have not yet arrived, and never unattended, limited to periods of no more than 5-10 minutes or so. Most of my time was spent measuring tube socket pin voltages and resistances against the HX-50 manual. I was able to find a few OT resistors, and a cap or two that were suspicious. I was focusing primarily on the PA, V111, 6DQ5, and the driver, V110, 12BY7A. Some of the pin voltages were way out, and the HV off the HV rectifier was running high, confirming that I was not pulling any HV current. The two relays, K101 & K102 were also not pulling in, leading me to the relay driver tube, 12AT7.
Attachment:
HX-50 BOT2.jpg
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To make a long story short, after twisting the anti-trip sensitivity control a few times, the relays began to kick in. Same thing with the band switch, which took a little exercise to get the PA to start pulling current. Resistor, R179, a 47 ohm 2-watt resistor, was also found to have drifted high by 100% so it was replaced. I can not get it to tune up much more than 150 mA on 80M, but for right now, I am thinking that filter leakage may be the reason for that. I may be wrong, in that assumption as I have not rechecked the HV at the rectifier, since getting output, but I didn't want to push my luck.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Mon 22, 2021 12:22 am 
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That's a really nice looking rig, Chris. Someday I hope to find an HX-50 to match up with one of my Hammarlunds.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Tue 23, 2021 3:34 am 
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Thank You Jeff, and good luck in your quest to find one of these beasts. I just sort of lucked into mine. I was not really looking for one, but it was there and the price was right, so it followed me home. One nice thing about these is that it is not all that heavy. At least I didn't strain anything getting it down into the basement shop.

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I just wanted to make sure that I did not pull a bone headed move here. :oops: When trouble shooting the PA circuit, this weekend, I found one resistor in the cathode circuit, shown above. It is a 10 ohm, 5% 2-watt resistor. I did not have any 10 ohm 2-watt resistors in my stock, but did have a few wire wound 10 watt resistors. I measured them out and selected one that measured out closest to 10 ohms and placed it into the circuit. My concern, in this circuit, is I have some concerned about the added inductance in the PA circuit. Am I likely to have issues with using a wire wound in this position. Should I replace this with a carbon comp, metal oxide, or another resistor type other than the wire wound? :roll:

It does tune up fine on 80m but have not tried it on higher frequency bands, as yet.

Thanks for looking. :D

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Tue 23, 2021 4:01 am 
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Generally not advisable to use wirewound resistors in RF circuits but in this case I think you're safe. Theres a 560 uH choke in series with the resistor, and the resistor is bypassed to ground with the .01 capacitor, so any small amount of inductance inherent in the resistor will be more than swamped by those two components.


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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Tue 23, 2021 4:36 am 
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^^^
Yes, what John said.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Sun 28, 2021 9:15 pm 
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It seems the hardest part is waiting on parts! :cry: I decided not to take a chance on using the wire wound 10 ohm resistor, as discussed above, and checked with a buddy that had what I needed. I installed a new 10 ohm, 2 watt resistor yesterday. I am still waiting on the filter caps to arrive from Hayseed Hamfest. They should be here early next week, if I can rely on what the USPS is telling me, that is.

I spent time yesterday, removing the old filter caps from the chassis. I had to pull out "Big Birtha", my American Beauty iron, to get enough heat mass to pull the old cap cans from the chassis. With the amount of congestion in and around the bottom side of the caps, it is like Hammarlund never expected these caps to be replaced. Just to confirm my decision to do so, I checked them on the Tel-Ohmike, and found the two HV filters to be very leaky. The 3-section LV can was not quite so bad, but I do not regret removing it from the chassis.
Attachment:
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The holes are now available, so I won't have to fight removing the old ones, when the new ones are available. All resistors connected directly to the filters check out within tolerance, so as long as I don't break off any leads reinstalling them, it should all go well. (I hope!). I don't want to have to wait, again, on any more replacements.

I also have tried using my Nikon Coolpix S9700 in stead of relying on my phone for shop pictures. It adds an extra step when trying to place in this site, in needing to reduce the picture size. For some reason, I do not have that issue with the phone shots. But at least I have finally gotten the Wi/Fi to work directly with my computer, without the need for a direct connection. (Saves wear and tear on the camera mini USB connector. I have much more control over exposures (which tend to be too bright) and the Coolpix works very well for the macro shots.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Feb Sun 28, 2021 11:21 pm 
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Your pics look fine.

I don't know why this is but every HX-50 I've seen looks like a big mess underneath. Hammarlund just didn't seem to put the effort into their transmitters that they did in their receivers.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Mar Mon 01, 2021 12:09 am 
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Quote:
Your pics look fine

Thank You Mike. I must admit that I am not as picky about my pictures as I was, years ago, when I was shooting with film. I shoot mostly for documentation purposes that I file with the radio info that I have, more so than any other reason.

Quote:
I don't know why this is but every HX-50 I've seen looks like a big mess underneath. Hammarlund just didn't seem to put the effort into their transmitters that they did in their receivers.


No kidding!!! You would never know this was built by the same company that built the HQ-120x, 129x....etc. I wonder if it was a different group of people designing and building the HX-50? Perhaps a new ownership, move to a new factory with new people? Shurely nothing like the receivers that I have worked on, anyway. There is one electrolytic cap in the HV box under the PA that I have no idea how to get out, without major surgery. It's C205, a 5 mF, 6 volt cap that is part of the meter circuit. I can't even see it, for sure, I just think it is there. Buried under a terminal strip. I am not even sure how critical replacing it would be. It looks like the band switch shaft would need to be removed, along with the last two switch sectors. Maybe more? They did no favors there, that's for sure. :x
Attachment:
HX-50-OUTPUT.jpg
HX-50-OUTPUT.jpg [ 410.78 KiB | Viewed 1122 times ]


Edit: Don’t know what I was thinking: HQ-173 and HQ-183? Been breathing too much CO2 thru a mask, I guess. :oops:

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Last edited by N9whh on Mar Tue 02, 2021 5:02 am, edited 1 time in total.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Mar Mon 01, 2021 12:21 am 
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Chris, hard-to-see components and places like that - that come up at least once a year - are exactly why I justified getting an EndoSnake borescope.

A cool little toy that I’ve averaged using every other month. :D

I don’t often use a bore scope, but when I do...

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Mar Mon 01, 2021 2:09 am 
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Quote:
I don’t often use a bore scope, but when I do...


Good Idea, Chuck! And I even have one! I bought one for some work I was doing on my Model A Ford, but it has been so long ago, that I forgot about even having one. Better yet, I even know where it is! I'll have to get it charged up and use it more often! Thanks for the idea! But that said, I am pretty certain the cap is where I think it is, and it will still need to be dealt with.

Thanks! :D

Edit: Well it is in there! Just like I thought! And the inspection camera did work!

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Chris
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Last edited by N9whh on Mar Mon 01, 2021 2:27 am, edited 1 time in total.

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Mar Mon 01, 2021 2:22 am 
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Very glad to help.

However, I must confess that though I purchased mine within the last year, there has been at least one time already that I didn’t think to use it. :roll: :oops:

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 Post subject: Re: Hammarlund HX-50 Transmitter
PostPosted: Mar Mon 01, 2021 2:39 am 
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Chuck,

I don't know if you saw my edit, but I did confirm that the capacitor is where I was thinking that it would be. I bought the camera to search for a suspected broken bolt off the starter Bendix that had fallen into the flywheel housing on the Model A. And yes, it was there. All I had to do there was go fishin' for it with a magnet. Even though it took me a few hours to find and fish it out, I think that may have been easier than replacing this cap may be.

Oh, BTW: I put the camera where it is now hiding in plain sight! :D

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