Halliscratchers SX-101 MK Nothing

[WA2OLZ]

FleaBay got me again. I just won (and overpaid for) a Hallicrafters SX-101, no MK, no letter suffix, no anything. At least, that's the way it was listed. I won't know for sure until it gets here. It is destined to become a stablemate to my SX-100 Mk II.

The listing said they know nothing about it but it pops their circuit breaker when turned on! That could be something simple or a world class issue. Again, we'll see! At any rate, I intend to pull the tubes before applying AC to the beast and go from there. Maybe even join Philip's capacitor replacing campaign he is doing on the transmit side of the equation on his Valiant.

I cannot seem to find a manual and schematic for the receiver anywhere online. They're available for the later Marks, but apparently not the mod zero. Any help out there would be appreciated.

-Jack

[n2bc]

Jack, wire a 60W 120V bulb in series with the SX's line cord.  If you have a short the bulb will be 60W bright but you'll not pop a breaker.

[WQ9E]

Hallicrafters made a lot of little running changes so even if it had the original manual there is a high probability there would still be differences between the manual and receiver.  I have never seen a "no mark" unit and I suspect the differences between it and a mark 1 would be very minimal.

Depending upon date of production the receiver may have a chassis heating resistor and later versions also added a separate filament transformer for the HFO.  One version of the manual has an addendum deleting the name "dampp chaser" and replaces it with resistor since Hallicrafters used the trademarked name of a  specific resistor product while they actually used a standard resistor.  In my receiver I found the separate filament transformer placed a significantly high voltage on the tube filament and I added a bit of resistance to bring it down.  The receivers are quite stable even without these added features.  

Be very careful with the dial, some of the SX-101 receivers have the same paint shedding common to the SX-62 series.

Once you get the electrical problems sorted out you probably will want to clean and lubricate the thrust bearing on the tuning capacitor.  I have 3 SX-101 series receivers and have worked on several and all had dry/crusty lube in the rear bearing leading to tuning that was far from smooth.

I had a SX-101 as my novice receiver and the Hallicrafters low IF variable selectivity system is one I like very much.  I use a SX-88 with my Ranger/Desk KW and have several other radio setups from this family of receivers (SX-96/HT-30; SX-115/HT-32B; SX-117/HT-44).  I much prefer the Hallicrafters method to that used by Hammarlund for their HQ-170/180/HC-10 gear.  The Heathkit RX-1 setup is a fairly close copy of what Hallicrafters used.

[K9DXL]

Jack, all variations of the SX-101 are nice receivers.  They just got a little more refined as time went on.  I'll second the comment about putting a lamp in series with the line cord. Ray, N0DMS wrote a several part article about the SX-101A starting in the September 2005 issue of Electric Radio.  Almost all of it will apply to your radio.  If you have a local AM station at 1600kHz in your area, you may have trouble with it getting into your IF, if so, try a wave trap on the antenna.  There's a lot about these radios on the internet.  Good luck!  (Hope you've got a strong back, it's a heavy beastie!)

[Pete, WA2CWA]

Briefly the differences:

SX-101 and SX-101 MK1: have 11 and 160 meters; no product detector.
SX-101 MK2: same as above plus improved stability.
SX-101 MK3: same as above plus oscillator filament is always on.
SX-101 MK3A: same as above except 160 meters dropped, 6 & 2 M converter position added, 11 meters retained.

SX-101A: 160 and 11 meters dropped, converter position added, product detector added, full 10 meter bandspread

And, as Roger pointed out, no one manual will be entirely accurate, even it you found the "exact" listed manual. Hallicrafters made a lot on the fly production changes, some of which were documented and some were not.
   

[WA2OLZ]

Lots of great info - all very much appreciated. Dampp chaser? wow! I call that a goldenrod in my gun safe 

I'll be doing the 60W bulb trick. Never heard of that one and it makes perfect sense.

Pete, I'll reach out for you when it actually gets here for docs.

I love this group!!!

Jack
WA2OLZ

[n3lrx]

Jack, wire a 60W 120V bulb in series with the SX's line cord.  If you have a short the bulb will be 60W bright but you'll not pop a breaker.

Ah yes, the poor mans variac! Sounds funny but it works because the circuit will see no more load than a 60 watt bulb even under dead short conditions..

[WQ9E]

If you have a local AM station at 1600kHz in your area, you may have trouble with it getting into your IF, if so, try a wave trap on the antenna. 

Very true but actually the IF is at 1650 Khz so that is where you need to check and the station doesn't have to be that close.  I had to put a wave trap on the one I use with my Valiant on 160 to get rid of low level interference from a "Disney station" on 1650 Khz. in Iowa that was over 150 miles away.  Pre-teen pop music didn't go well with vintage AM

The SX-101 uses a crystal controlled second conversion oscillator with crystals at 1600 and 1700 Khz. to convert the 1650 first IF to the ~50 Khz. second IF.  Properly aligned you can tune in an AM station and switch sidebands at will with no change in audio quality (other than hopefully avoiding interference).  But sometimes these crystals drift a little bit and if this happens you can align the final IF to a slightly different frequency to retain proper operation.  If one or both crystals are slightly off PM me and I will send you a brief explanation of the process.

[K9DXL]

Thanks for reminding me Rodger.  Yes, 1650.  New stations on the expanded AM BC band can create a problem.  I appreciate the correction.

[K9DXL]

Right on target, Rodger!  I understand that back in the 30s when WLW in Cincinnati was authorized 500,000 watts people in the area often heard the station on fixtures and devices that were not radio receivers at all.  One story even says the power meters at Cincinnati Gas & Electric sometimes bounced in sync with the VU meters at the station.  Imagine 250,000 watts of audio to plate modulate that beast!  There are some internet sites with pictures of WLW in its glory days, including modulation transformers, reactors and chokes the size of two story houses.

[n3lrx]

Wow.. 500 Kw. Those were the good old days of AM Radio! Was it WLW that had the lake out front to cool the finals or was that someone else?

[WA2OLZ]

 

It's not going to work out, unfortunately.

The seller on EBay was the ultimate honorable seller. After I bought the rig, and before it shipped, she contacted me and let me know the Pitch knob got broken as they prepared the rig for shipment. Ouch! A few photographs later it was apparent the shaft was broken off, not the knob. It must have been hit pretty darn hard. We reversed the sale.

Maybe some of you with far more experience and expertise could tackle it, but it's too much for me. Contact me offline if you want me to pass along the seller's info.

73
Jack
WA2OLZ

[Todd, KA1KAQ]

Food for future thought, Jack. I've had similar reports from people of radios 'popping the circuit breaker' that were actually popping the GFI outlet. A lot different as this is usually caused by leaky line bypass caps.

Just something to keep in mind, and sorry your radio got smacked. The good news is, there are a LOT of SX-101s out there. I'm still looking for a very late SX-101A with the later style knobs myself.

I understand that back in the 30s when WLW in Cincinnati was authorized 500,000 watts people in the area often heard the station on fixtures and devices that were not radio receivers at all. 

Similar stories abound about the big Marconi spark station MCC/WCC at South Welfleet MA back in the day. Stories of people picking up CW on all kinds of odd items, women getting RF burns while hanging out the wet laundry, etc etc.

Those were the days...when radio was radio, men were men, and sheep were nervous....

[WQ9E]

Todd,

Good point about the GFI breakers!  Even a bit of residue on an extension cord plug can trip them in humid weather and the leakage current from line bypass caps is certainly enough.

Damage to those BFO shafts is not uncommon, the shaft is of small diameter and fragile.  But the SX-101 series is common and there is no reason to go into purchasing one with issues unless the price is really low.  I had one as my novice receiver and it remains a favorite of mine.  I have been keeping my eyes out for a true parts unit in this family of receivers so that I can build a Hallicrafters version of the Hammarlund HC-10 external SSB adapter for use with other receivers.  I much prefer the Hallicrafters system.

[WA2OLZ]

Agreed, guys. They are nice receivers but fortunately (so far) not made of unobtainium. This one was a bit overpriced anyway but the shaft issue settled it for me.

So far as the popping breaker, I never thought about the possibility of it actually being a GFI. That could well be it. I was thinking maybe as simple as a frayed AC cord, sorted primary or something.