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Author Topic: Anna's SX-42  (Read 10684 times)
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WQ9E
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« on: November 14, 2010, 02:54:03 PM »

It has taken awhile but my daughter's SX-42 is now finished.  This was a pretty typical restoration for a Halli of this time period; lots of wax paper caps to replace and a large number of out of tolerance resistors.  Given my past experience, I just replaced the 4 mica caps in the discriminator circuit during the initial work.  I also thoroughly cleaned and lubricated the tuning mechanism.  Hallicrafters didn't include a fuse so I added one along with an inrush limiter and a new 3 wire cord set.  The line bypass caps in this model are mounted directly on the power transformer under a metal shield.  The mounting is awkward because the transformer is held in place by the screws that also hold the bottom transformer shield and there are also mounting brackets held by these same screws that hold the top transformer cover in place.  Keeping everything in the right place while lining up the hardware is not so much fun.

Upon power up there was lots of audio, no smoke, but the higher bands were dead.  A quick check showed no voltage on the screen of the 1'st RF amp and the culprit was a badly burned resistor hidden under the band switch-probably a casualty of when it was operated with bad caps.  About 20 minutes with a pair of long needle nose pliers and a set of tweezers allowed me to remove the old resistor and replace it with a new one.  The receiver now worked well except on the highest range (55-108 Mhz.) where sensitivity was very poor.  I traced this to a broken lead on the oscillator coil winding that couples the oscillator output into the mixer section.  I let it cook for an hour and then performed a complete alignment last night and it works very well.

Today Anna got to take it for a test spin and now she has to clear out a place on her table in her bedroom so we can move it up there.   Santa brought her a NOS Science Fair Globe Patrol 3 transistor regen SW kit last year but she is definitely stepping up in performance with the SX-42 AKA "Her Greenliness"  Anna has listened in on the regional AM net when I am NCS via her SW regen but the SX-42 should do a good job of bringing in all of the action.

 


* Anna's SX-42.JPG (1433.69 KB, 1620x1080 - viewed 636 times.)
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Rodger WQ9E
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« Reply #1 on: November 14, 2010, 03:17:28 PM »

Sounds and looks like a good job.  Have not found one of those that the current owner is not too proud of; could be because I'm too cheap maybe.  Still looking for a minor problem with the S-77 after recapping, etc, and removing the garage grease from a previous [non-ham] owner.  In process of refurbing my S-85 I bought new as a Novice in 58.  Of course, the 85 is just a newer 77.
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73,  Mitch

Since 1958. There still is nothing like tubes to keep your coffee warm in the shack.

Vulcan Theory of Troubleshooting:  Once you have eliminated the impossible, whatever remains, however improbable, must be the truth.
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« Reply #2 on: November 14, 2010, 04:46:23 PM »

Looks like a happy girl with a fine old radio!

?? What  are you using for an inrush limiter?

73, Bill
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WQ9E
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« Reply #3 on: November 14, 2010, 06:40:16 PM »

Looks like a happy girl with a fine old radio!

?? What  are you using for an inrush limiter?

73, Bill

Bill,  

Thanks!

I used a CL-200 from Mouser:  http://www.mouser.com/catalog/catalogUSD/642/585.pdf

Although low tech they are simple to use and reduce cold inrush current.  It takes some of the stress off switches, tube filaments, etc. and allows you to fuse closer to actual current draw without having nuisance fuse blowing.
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Rodger WQ9E
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« Reply #4 on: November 14, 2010, 06:54:41 PM »

Wonderful!

She sure looks like one happy YL!

Great job.
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KA8WTK
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« Reply #5 on: November 14, 2010, 06:54:57 PM »

Nice radio! Should sound pretty good with the R-44 speaker. She will enjoy that!
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Bill KA8WTK
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« Reply #6 on: November 14, 2010, 07:58:40 PM »

Indeed, you area kind-hearted ham to do that for her.  Kudos!
 
Cheesy

73DG
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« Reply #7 on: November 14, 2010, 08:06:33 PM »

R,

You have a very lucky daughter.


 Are you looking to adopt a son???   I could use an AN/SRT-14. I can clean up after myself and will not complain when I have to take out the garbage.... ..


klc
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WQ9E
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« Reply #8 on: November 14, 2010, 08:17:09 PM »

R,

You have a very lucky daughter.


 Are you looking to adopt a son???   I could use an AN/SRT-14. I can clean up after myself and will not complain when I have to take out the garbage.... ..


klc

To be considered for adoption you have to come equipped with either a Meissner 150B or Halli HT-20 Smiley 
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Rodger WQ9E
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« Reply #9 on: November 15, 2010, 10:43:12 AM »

Might want to include a "V" chip for 75 meter phone.    Undecided

But in all seriousness, I started out at age 10-11 with an S22R.   It is a great way to get started.
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W3GMS
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« Reply #10 on: November 16, 2010, 08:25:27 AM »

Rodger,

What a great looking receiver and I know the inside work you did is top notch.  Anna will remember you doing that for the rest of her life.  As has been stated, her second receiver is quite a step up in the receiver world! 

My early receiver back when I was 12 was a GR-64.  Certainly many steps below the SX-42! 

I do have an SX-42 here that awaits restoration. 

I am sure you enjoyed every moment of the restoration knowing who the receiver was going to.
 
Regards,
Joe, W3GMS   
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« Reply #11 on: November 16, 2010, 09:18:25 AM »

Joe,

Thank you for the kind comments and I really put a lot of thought and care into this restoration.  I have an SX-42 coupled with a HT-19 but the tuning feel on mine isn't quite as smooth.  But I am glad my daughter has the better one.

My very first shortwave receiver was a 2 band Sharp tube type 2 speaker table radio my brother sent to me while he was in Vietnam.  It didn't have a BFO but it got me interested in shortwave radio and I still have it.  Later my parents bought me a Radio Shack Science Fair Globe Patrol which is a 3 transistor shortwave regen kit.  Amazingly enough Santa found one NIB for Anna last year so that was her first attempt at soldering.  Maureen and I usually get a weather report (from Chicago WBBM) via Anna at breakfast every morning since she has been turning on the Globe Patrol in the morning. 

The SX-42 really isn't that difficult to work on.  Although some of the capacitors in the front end are a little difficult to access they can be replaced by working through the removable access plate on the side of the receiver.  Otherwise you have the usual leaky wax paper caps and a number of out-of-spec resistors.  The crystal filter element isn't well sealed so unless you clean it in alcohol and reassemble you will probably be disappointed with it but once cleaned up it works very well on CW.  After cleaning I check these crystal elements by attaching them in series between the scope and signal generator to check for a clean sharp peak.  Some of the holders used by National in the NC-173/183 style filter have a slightly compressible gasket and if you tighten the case screws too much it noticeably increases the loss through the crystal so on these I do the final tightening while it is hooked to the generator and scope.

I think it is beneficial on this receiver to replace the 5U4GB rectifier with SS rectifiers and a dropping resistor.  The power transformers on the SX-42/62 run very warm and the 15 watts of rectifier filament load is a significant part of the overall transformer load.  After switching my SX-42 and 62A to SS the transformer just runs comfortably warm so I did the same for this one (on a plug in base) during the overall restoration.  I did disconnect and tape the 5 volt leads so that B+ is also removed from this winding.
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Rodger WQ9E
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« Reply #12 on: November 16, 2010, 03:02:20 PM »

Excellent job and story, Rodger. You've done something many others should be doing now. Rather than whining about the 'death of amateur radio', you've introduced and encouraged a youngster with the magic of radio. That's the only long term path of salvation for our beloved hobby. While pulling in more folks in our own age group is a plus, it's a temporary fix at best, a band aid. As the old saying goes - the kids are the future.

Just curious though - does she have to wait until graduation for the R-42?  Grin
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« Reply #13 on: November 16, 2010, 03:12:06 PM »

Rodger,
I am glad your daugther has the better SX-42  Smiley  I wonder if she has shown any interest in becoming a Ham?  She is a seasoned SWL at this point.  I will never forget the WPE3GJF Popular Electronics SWL call sign I got when I was 11 years old or so.  

Thanks for the tips on the SX-42 and I will take your suggestions when mine becomes "belly up" in the GMS lab.  Right now I working on an HQ-160 but its nearly done.  Concerning the 42, I had heard that the bandswitch were sensitive to certain types of cleaners.  I forget if it was related to HV being on the bandswitch but more than one person mentioned that to me years ago.  The 42 is a really sharp looking receiver.  A good friend of mine Fran, W3SCC has one that he has been using for years.  I believe I actually have (2) SX-42.  One is in much better physical condition than the other.  If you ever need parts for either yours or your daughter I would be happy to help you out if I can.  

Regards,
Joe, W3GMS            
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« Reply #14 on: November 16, 2010, 04:20:48 PM »

Todd,

The story on the speaker is that I was first going to restore a SX-43 for her and a friend (Thanks Ken W0HRO!) picked up the matching speaker for it at Dayton.  Then I came across the SX-42 in the for sale section here so we upgraded.  I do have a couple R-42 speakers but the little speaker will better fit on a shelf above her dresser.  In the bass boost position the R-43 has distortion if there is a lot of low bass but since Anna (wisely) despises rap that won't be a problem Smiley

Joe,

I think there is a good possibility of a license in her future.  She is really into science at this point and radio fits in perfectly.  We spent some time outside in the wonderful weather last weekend so she could try her hand at direction finding with an older marine type receiver.  I strategically left one of my old PE magazines with a Carl and Jerry story in it for her to find and she asked if I had any more so that part of the electronics education plan is working perfectly Smiley

Thanks very much for your offer of parts but I hope I never need to take you up on it Smiley  The SX-42 and 62 both have a potential band switch problem because of the way the receiver is set up with only one RF stage on the BCB so B+ ends up on the band switch.  If anyone used one of those lubricating cleaners that has attracted dust it is easy to create a carbon path across the switch.  I guess I have just been lucky but I have a SX-62A in the office and a 62 and 62A at home along with the two SX-42 and I haven't had a problem yet.  But I do clean the band switches carefully.  The worst case was the first SX-62 I restored, a previous owner had coated the switch area with so much gunk that it killed the HFO on the highest two ranges.  I resorted to using electrical motor commutator cleaner and then lubricated the detent and shaft sleeve and 7 years later it is OK.  I am probably very lucky that one didn't cook the wafer. 

Make sure you replace the line bypass caps in your SX-42.  There is no fuse and if one/both short they are probably going to cook the exposed transformer.  I have an RME-45 that was set up the same way and when I got it the bottom paper of the transformer was turned to ash.  It still tested OK but I replaced the transformer with one from another parts unit because I didn't trust the original to be OK.
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Rodger WQ9E
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« Reply #15 on: November 16, 2010, 05:01:33 PM »

Rodger,
Thanks for the refresher coarse on the bandswitch issue with the 42.  Now I know what not to clean it with!  Maybe I will luck out and the switch in mine will be ok.  I appreciate the comments about helping protect the iron as well. 

Yep, it sounds like your daughter will definitely become a Ham based upon your observation.  I am curious if she has tried to copy any CW?   My wife Martha is an excellent CW op.  She learned it very quickly and became very proficient in the mode.  The 1921 3ZO station in Parkesburg had a YL CW that was very well known for her CW ability.  A lot of ladies really seem to excel at CW. 
Regards,
Joe-W3GMS
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« Reply #16 on: November 17, 2010, 09:03:29 AM »

Rodger and Joe,
                      Just FWIW, some years back, I had an absolutely MINT cosmetic condition 42 that the previous owner had really soaked the bandswitch with some kind of oily/greasy lubricant. To say it made a "carbon path" is probably the understatement of the century. Mine actually went up in flames!! The arcing lit the oil soaked wafer off and the rest was history. Cry  Cry

For some wierd reason the phenolic wafers on some of those old radios were very porus, and would soak up anything that came in contact with them. That is what happend to that one.

If I use anything oily to clean them, I immediatly wash it off afterwards with a really good degreaser to remove all of it after I'm done. And make sure that there is ABSOLUTELY no oily residue left on or in them!!

ONCE BITTEN, TWICE SHY! ! ! ! !
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« Reply #17 on: November 17, 2010, 10:42:34 AM »

I think what saved mine from the flames of death was that I cleaned the switch thoroughly during restoration.  What I didn't realize was how badly the PO had also soaked the coils and trimmer caps and this kept the oscillator from running.  I remember my first attempt with a grease remover I got range 5 working but range 6 would still cut out around 70 Mhz. and the commutator cleaner was the only stuff that worked for me. 

A lot of the common cleaners are very flammable and WD-40 is very flammable (basically kerosene plus a light oil).  WD-40 was used by a lot of folks as a starting aid for the older diesels since it is quite a bit less explosive than ether but it still ignites very easily.  My well driller friends showed me a pressure switch housing that a customer had blown up with WD-40.  He tried to fix an intermittent switch using WD-40 and he pretty much filled the housing up and then put the cover back on.  It was fine for a couple of minutes until the pressure setting was reached and the contacts opened creating a nice little spark that blew the cover off the switch.  The drillers had already nicknamed this guy Explosive Ed because his water source has a fair amount of natural gas in the water and when he had an old working head pump about every couple of years enough gas would build up in the pump house to blow it up.  Smiley
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Rodger WQ9E
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« Reply #18 on: November 17, 2010, 10:52:08 AM »

Frank & Rodger,
Very informative on the bandswitch issue and what not to use to clean them.  Maybe just a non lubricant type of cleaner is the ticket for such switches that have HV on them.  Maybe some good tape head cleaner that I use on Real to Real machines would be something to try.  Spray a small amount on a piece of old slate tile and then put a match to it and see what happens!
Regards,
Joe, W3GMS
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« Reply #19 on: November 17, 2010, 07:47:48 PM »

Ah, the flaming band switch! I had a SX-43 switch go up in flames one time. It is NOT a pleasant experience.
The real key with any cleaner, IMHO, is to use as little as possible and only on part of the contacts. The part I mean, with a Halli switch or similar, is the flat part that rotates. If I get just a little on the moving flat contact it seems to transfer to the "wiper" half of the contact. A tooth pick dipped in the clanner seems to be enough most times. I never spray cleaner into a radio.
Just my two cents worth.....

Bill KA8WTK
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Bill KA8WTK
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« Reply #20 on: November 18, 2010, 08:44:06 AM »

If I have to clean a bandswitch in one of those old receivers, I usually use a mix of lacquer thinner and mineral spirits. (somewhere around 50-50 to 70-30 with the bigger number being the lacquer thinner) And use that to wash the switch out using a small modelers or artists paintbrush.

YES, IT IS EXTREEMLY FLAMMABLE! ! !  But it evaporates very quickly taking any oily residue with it. Just be sure to have the set powerd down, unplugged, and dont smoke while doing it. And be sure to let it dry thoroughly before reapplying power. It has worked for me every time.
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« Reply #21 on: November 18, 2010, 11:02:02 AM »

We used that approach YEARS ago to clean office equipment like typewriters (a wha...?). Works great for cleaning out all the crud, but yes - be sure to dry it off well and avoid any source of combustion in the meantime. Otherwise big, BIG boom!

The other issue with cleaning these old band switches with DeOxIt and the likes is the tendency of the phenolic wafers to swell and render the switch inoperable. Later phenolic is apparently sealed somehow so it doesn't do this (lighter brown vs. a redder brown), but I learned the hard way with my SX-28A. IIRC, I had to use alcohol to clean the wafer and remove the stuff. It still turns hard to this day as a result.

The best way to address the problem is to use a swab soaked in cleaner and hold it against the plates of the switch between contacts, allowing the cleaner to clean the contacts when switched back and forth. Unfortunately, not all wafer switches allow this level of access or even visibility. Patience is the key.
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known as The Voice of Vermont in a previous life
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