Hallicrafter's SX-42... a BAD restoration!

[W9LBB]

Howdy!

Sometimes when it rains, it comes down in BUCKETS!

This last week I was gifted a couple of major hunks of gear. This one is gonna be
ROUGH tho.

I got hold of a Hallicrafters SX-42 which has been BADLY stored. For Gawd knows
HOW long (10+ years!) the rig has been living, without cabinet, in the loft of an old
dairy barn; it came to light when the barn was about to be demolished! 

The GOOD news first... the rig is 99% complete, and I have the proper cabinet for it.
In fact, among the stuff socked away I found TWO of 'em that only need repainting.

Along with the radio I found a carton containing a LOT of NOS tubes for the rig. A
quick pass thru the Hickok 539C smoked out two bad tubes (audio phase splitter and
an IF amplifier).

There are some modifications, but nothing too serious; they're on the rear apron and
don't show. A couple of extra holes drilled (ventilation?), and some connectors have
been changed.


The BAD news...   when I pulled the bottom plate I discovered that I was evicting
several generations of field mice! The shop vac removed a large mouse nest in the
power supply / audio area.

Some wiring has been stripped clean of insulation by critter teeth seeking building
materials, but it's not too bad; they got a few single wires, but it doesn't look like
they weren't ambitious enough to attack the wiring harnesses. After getting out the
nesting crud, the underside doesn't look all that bad.

The topside tho...  this is where it gets interesting.

ABSOLUTELY FILTHY!!!  Besides the usual chassis crud, there's a couple of areas
that have serious rust patches. My biggest concern is the variable caps; the top
cover over them is missing, and they're quite dirty and have a film of corrosion (?) on
the cap plates. Any suggestions on cleaning that up? First thought; take them out
and put the variables thru the dishwasher, primed up with strong detergent and
some ammonia!

As far as the chassis rust is concerned; I'm thinking get it off with a wire brush and go
at the areas with sandpaper and / or Dremmel took to get to bare steel. Once I'm at
that stage replate zinc onto it.

The front panel...   not certain yet, but I think a complete refinishing is called for.
Has anyone here had experience with getting a panel silkscreened?

That big, Lowe inspired dial and S-meter are in dirty but usable shape.

Interestingly, the radio doesn't seem to smell of mouse droppings like I'd expected it
to.


There are some parts needed.

Does anyone have a BFO knob? This one is smashed.

Also...   the LOCK knob (and shaft???) that is in the center of the main tuning dial
is missing.


The radio is in tough shape, but it's FAR from a parts set, IMHO.

ANY suggestions on getting this old lady up and running would be appreciated!


73's,

Mr. T., W9LBB

[w3jn]

This thread belongs in the tech forum (this forum being for completed tips/projects only), but here's my experience.

I'd remove the dial, S-meter, and front panel and take the thing to a car wash and douche it really good with hot soapy water.  Then, put it in the sun to bake, or perhaps a 140 degree oven, open it once in a while to let the humid air out.

I wouldn't worry too much about the chassis corrosion, the only way you're gonna get it all off is to stip the chassis entirely (which you DO NOT want to do on this radio!).

Things to watch out for:

1)  Caps associated with the tone control switch.  If they short they take the output tranny with them.  Replace before you even think about powering it on.

2)  The tuning caps will prolly clean up.  Burnish the brass finger contacts and apply a drop of deoxit.  A bit of teflon grease on the bearings will make it Fine Business most likely.

3)  Recapping the RF secion is a major pain.  There are bypass caps in there that have a wire braid for the ground lead.  I'd leave 'em in, those don't seem to go too awfully bad and they're in the cathode circuit.

4)  The bandswitch is very prone to failure in this radio, due to the fact that it switches B+ and a failed bypass cap dumps the B+ to ground thru the switch contact.

5)  Beware the mica caps inside the IF xformers.  When aligning you should get a nice sharp peak.  If it's very wide tuning or no peak at all, the micas are shot and need to be replaced.  You can do this w/o yanking the whole xformer, just pull off the cover.

6)  The gizmo in the center of the tuning knob is to flip between bandspread and main tuning.  There's a little clutch mechanism that does this, and for some reason those things always go missing.

7)  There are at least 3 different versions of this radio that I'm aware of (the BAMA schematic is different from the SAMS photofact is different from the last one I worked on!)  Differences mainly revolve around the FM detector and AVC rectumfrier.

Good luck, and feel free to post if you run into any trouble.

73 John

[The Slab Bacon]

I have had 2 of these animals in the past years and currently still have one of them. They are a wonderfull receiver with audio to die for, however they are somewhat a pain in the ass to get going sometimes. Like John said, they made changes without telling anyone about. Mine (electrically) looks very different than the skizmatic in the factory manual. The circuits in mine look more like its cousin the SX-62, with a very different detector / avc circuit.
           If you are serious about this receiver, plan on a TOTAL recapping and a little troubleshooting to bring her back to life. Also watch out for the RF choke that isolates the filaments in the front end, they do open up for no reason. My current one swallowed up something like 47 caps, 12 or 13 resistors, and 1 RF choke before coming back from the dead!
           If you do do all of the work, you will be rewarded with some awsome audio!!

                                                                    The Slab Bacon

[W9LBB]

Howdy, Guys!

Thanks for the replies on this one...   and sorry I posted in the wrong area.

And THANKS for the warning about those tone control caps!!!

Work has been insane lately, so not a whole lot of time to tinker with a 60
year old radio, but things should lighten up soon.

It looks like the best approach on this rig is to get back to basics; start at the
power supply and get the rail voltages up to par and cleaned up (i.e., new
electrolytics). After that's working OK, move to the audio output and phase
splitter stages, and just work forward toward the antenna connector, one
stage at a time.

Again, thanks for the information.


73's,

Mr. T., W9LBB

[The Slab Bacon]

Tom,
       If you are really serious about that rx, you should replace all of the paper and electrolytic caps before you even think about putting any juice to it. If it has had really bad (damp) storage, it will save you from frying other stuff due to shorted caps.
I didnt do that to my first one and sent the bandswitch up in flames! In 42's amd 62's the bandswitch a miserable s.o.b. to even think about changing. I didnt take that chance with the second one. Recapping will save you a lot of grief further down the line.
                                                  The Slab Bacon

[KB2WIG]

For the mouse turdletts, get a hepa mask if you stick your noise in this thing... them critters carry a lot of bad stuff...like my mommie says, wash yo hands. The car wash works; I'd take along a 5 gal container of water to slowly flush the soap, etc out of the chassie... FYI, rodent urine is florescent.... its a good way to find out where the critters egress/engress... they dont stop to piss, they generally leak all the time....  Dr. Wissard

[K8WBL]

Beautiful radios, won some design awards, I have one that still not working, traced it to I believe a bypass cap somewhere in the IF section.  The newer version of this has a 2 piece bandswitch - factory finally agreed with the original 1 piece, that it was just too difficult to repair and replace.  Things get real tight in there, one reason why I havent finished repairing mine.  I'm afraid I might burn up the power transformer.

73, Tim K8WBL

Send some pics

[KM1H]

Dont have a 42 but own a pair of SX-62A's cousins that Ive completely gone thru; all 42 caps and bunches of resistors. Had to fabricate tools to get at the ones under the bandswitch.

One sits in the office feeding the 4 speakers in a 50's RCA "Orthophonic Hi Fi" console which is another name for mono. What an absolutely great sound.

The other is in the BR driving a R-42 bass reflex speaker which is also quite nice.

I use them strictly for AM BCB, SW and FM.

Carl
KM1H

[k4kyv]

One sits in the office feeding the 4 speakers in a 50's RCA "Orthophonic Hi Fi" console which is another name for mono. What an absolutely great sound.

Webster's New Millennium™ Dictionary of English
Main Entry:     orthophonic
Part of Speech:     adj
Definition:     reproducing sounds authentically, enunciating correctly

Webster's New Millennium™ Dictionary of English, Preview Edition (v 0.9.7)
Copyright © 2003-2008 Lexico Publishing Group, LLC

http://dictionary.reference.com/browse/Orthophonic

[W2XR]

Actually, I thought that the RCA Orthophonic system was RCA's brand name for their equipment that utilized the RIAA record/playback EQ curve popularized for 33-1/3 RPM records in the late 1940s.

73,

Bruce

[KM1H]

Actually, I thought that the RCA Orthophonic system was RCA's brand name for their equipment that utilized the RIAA record/playback EQ curve popularized for 33-1/3 RPM records in the late 1940s.

73,

Bruce

Whatever it was called in the marketing department at RCA it sounds great. The full name on the front plate is "New Orthophonic Hi-Fi". The Orthophonic name goes back to 1925 at Victor.

And: http://tenwatts.blogspot.com/2008/07/orthophonic-sound.html

I forgot to mention that Ive slightly modified that SX-62A (also pulled the 6V6's to cut down on the cabinet heat) to take the low level audio into the RCA which has a seperate audio deck with PP 6V6's along with Loudness, Bass and Treble controls. The speakers are 2 each 10" and 4". The best part is that the console was free from Craigs list.

Carl
KM1H

[Todd, KA1KAQ]

Tom -

Good information from folks to get you on your way. I'd add only two things:

First (and I know this might offend someone's sensibilities, just trying to be practical) - depending on the overall level of deterioration, you might want to consider finding a cleaner/less destroyed version to put your time into. This unit could make an excellent donor. With the corrosion you mentioned along with the mouse pissolene and other issues, it could end up being a never-ending repair, one thing going bad after another is fixed. Dairy barns tend to be very damp/humid for a number of reasons, so there's a good chance that you'll have hidden damage in transformers and elsewhere just waiting to rear its ugly head. As others have said, the bandswitch issues along with component layout are a pita on a good day. Just something to consider.

Second, pay special attention to what John said about the little 'T' bar knob that controls the clutch. These often snap off due to binding that can be caused by anything from a bent shaft to crud inside the hollow tuning shaft that surrounds it, to stiffness internally crated by too much resistance in the clutch mechanics. You don't want to snap off that tiny threaded shaft.

If you need parts for the rig, I gave away a donor chassis to Roy Morgan K1LKY and Bob Sullivan W0YVA a few years back to share with anyone in need. I know Roy only needed one of the cover stand-offs, not sure what Bob needed but there's bound to be a lot left. Think I also have another kicking around that is partially stripped.

Whatever you decide to do, good luck with it. You'll need it.

[KM1H]

I have a SX-62 (non A) chassis that I can remove some parts off  if needed. It should share many components with the SX-42. No front, knobs, power or audio iron.

Carl

[N3DRB The Derb]

orthophonic was the name given to the 'ultimate' Victor sound reproducer (or box) in their last line of Victrolas. I have one of these, and serviced they actually have some frequency response up and down the audio range. I dropped mine on a concrete floor 10 years ago breaking the pot metal mounting neck of it, I've never gotten it fixed.

great fun playing 78's when the power is out by oil lantern.

[WQ9E]

One problem I found on two of my 3 SX-62 series and on my SX-42 was a leaky cap in the discriminator which causes poor operation on FM.  Operating properly these receivers sound very good on all modes!  This also is the vintage of Hallicrafters that seems to have a number of the higher wattage resistors out of spec and I found several of these in the ones I have restored.

The SX-42 is a nice receiver and definitely worth the effort.  In my 1949 handbook the Hallicrafters ad introduces the "New SWL" version of the SX-42 (which is of course the SX-62) for $269.50; the SX-42 is listed on the same page at $275.00.  For $5.50 more I would definitely give up the calibrator built into the SX-62 and take the nicer tuning mechanism, variable BFO, and crystal phasing controls of the SX-42.  I used an SX-62A for one week as a novice before moving up to an SX-101 and given the backlash and the fact that the 40 meter novice band only covers 1/8" of dial the crystal filter is pretty much useless on the SX-62.  But the SX-62 is a great broadcast, shortwave, and FM band cruiser and is one of the radios that "non-radio" guests flock to.

Another nice sounding Halli on FM broadcast is the S-36A.  If you get the common Navy version of this set bypass the "radiation suppressor" tube added to the front end and the sensitivity is much better (and you will have a spare acorn tube for use in the receiver).  The S-36A uses a lower frequency IF (in the 5 megahertz range as I recall) and needs to have the "demphasis" changed for current FM BCB standards.  My S-36A has less warm up and detector drift than my SX-42 and 62 receivers and after 1 minute of warmup it stays in place with no retuning needed.  It is probably also the heaviest Halli receiver I own (or at least ties the SX-88) but they seem to show up cheaply at times and are worth grabbing.

Rodger WQ9E

[WZ1M]

The problem with the three 42's I have is that none of them are the same underneath. Production changes up the ying yang. I now have, I think, five different schematic digrams for the SX-42.
Gary...WZ1M