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 Post subject: Got a new toy today.
PostPosted: Jul Tue 12, 2011 6:03 am 
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Fired it up and it even works, sort of.

Looked it over for a while and it appears untouched. Checked voltages, with 117 AC in, on rectifier and some plates, most within 5% or so, that was a big surprise. I'll start the clean, adjust, align process tomorrow. The dial/tuning gear train is in need of serious cleaning for starters. First Hallicrafters I've owned in about 55 years, the other one was an S-38C.
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Last edited by Mikeinkcmo on Jul Wed 13, 2011 11:38 pm, edited 1 time in total.

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Tue 12, 2011 8:21 am 
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Very nice SX-101, I have one for at least 35 or more years although I have not turned it on in 25 or so years.

One receiver I would like to own is a SX-100 general coverage receiver.

Sal

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Tue 12, 2011 12:54 pm 
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My SX-101A is on the floor, apart... have too many other radios coming in
to do my own projects lately. I'll be interested to hear how you like that
receiver. I see it is the earlier model with 160 meters and no PD.

Pete

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Tue 12, 2011 1:53 pm 
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A SX-101 was my novice receiver in 1975, well actually it was my second receiver because the first week I used a SX-62A which had a bit of a lack of bandspread issue :) The SX-101 remains one of my favorites and it traces its heritage back to the S-76 which was the first of the Halli receivers with the 50 Khz. final IF.

You will want to replace the tubular paper caps before going far, the colorful bands are pretty to look at but it doesn't compensate for the leakage. You will probably find a number of these caps also have the bodies cracked open.

You may find some of the drive problem to be dried grease in the thrust bearing of the tuning capacitor, this is very common on Hallicrafters of this era. Turn the cap to full mesh and then remove the thrust bearing, the bearing itself may come off with the holder or it may remain in the shaft of the capacitor. Clean off the old grease completely, WD-40 is a handy solvent for this purpose. Re-lube with a good quality synthetic grease. Then reinstall and tighten the bearing only to the point that the rotor plates are centered between the stator plates. Look directly down from above to avoid parallax error while making this adjustment. Also use some light synthetic oil on the front bearing. You will also need to lubricate the various gear shafts in the drive mechanism.

One problem you may run into is that one or both of the second conversion oscillator crystals may have drifted off frequency. They should be exactly on 1600 and 1700 Khz and mix with the first IF to produce the final low IF. If one or both crystals have shifted slightly, you can compensate via modifying the alignment procedure. The final IF should be aligned at 1/2 the difference between the two crystal frequencies + .5 Khz. (changed to .75 Khz. in later models). Now assume you measure the 1700 Khz crystal as having drifted to 1702 while the 1600 has remained on frequency. The difference between the two is now 102 Khz half of which is 51 so your new target frequency for the final IF is 51.5 Khz. Note that the BFO must also be aligned to the new difference frequency which of 51 Khz.

The SX-101 is a very good AM receiver but sometimes people are thrown off by its filter/detection system. It is designed to only receive one sideband on AM and you can select either upper or lower to avoid interference. Once the receiver is properly aligned, turn the BFO on with pitch set to zero and tune the AM station in zero beat. Now turn off the BFO and choose whichever sideband has the least interference. The 5 Khz. selectivity position provides equivalent bandwidth to a conventional receiver with a 10 Khz. bandwidth. Properly tuned, the 2 Khz. position can be used under high QRM conditions on AM.

For quite a while I used a SX-101 with my Johnson Ranger/Desk KW station because I found the HRO I was using didn't have enough selectivity under really poor conditions. I am now using a SX-88 which is a nice receiver and looks great but it doesn't have the switch selectable sideband feature of the later family members; you have to use the band spread tuning to select the desired sideband on AM which isn't nearly as convenient.

Rodger WQ9E


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Tue 12, 2011 2:42 pm 
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You wont be dissapointed, it is still a Hallicrafters :lol:

Besides Rogers comments they are deeef on 10M as compared to the competition or the SX-115 which is the only real good Halli ham band radio.

I do use a SX-101A occassionally and its fine for nostalgia SSB use with the GSB-100 but the SX-115 gets the nod with the HT-32B.

Carl


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Tue 12, 2011 3:46 pm 
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You can improve AM distortion considerably if you clip one end of the .047 cap in the noise limiter circuit.

Also, figure on replacing the 12BY7 LO tube... they run hot and the fil is always on as I recall.

Carl, I never noticed a deafness on 10 with any of the SX-101As I've had. My standard weak signal at home was a 10M beacon in Baltimore on 28.297 - if it could hear that, it was about .5 uV sensitivity, and none ever failed to receive it fine.


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Tue 12, 2011 4:08 pm 
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Nice SX-101...I'll second Rodger's comments.

Sal Brisindi wrote:
One receiver I would like to own is a SX-100 general coverage receiver.

Sal


Sal:

I have a "spare" SX-100. It is in very good cosmetic condition, works, but has not been recapped, etc. I would be willing to trade it for Fisher tube stereo audio or a pair of mono blocks. Contact me via PM if you're interested and what you have for a straight up trade.

BR,

Terry


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Wed 13, 2011 6:14 pm 
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wow original bumble bees :shock:


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Wed 13, 2011 6:17 pm 
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tubeAMP wrote:
wow original bumble bees :shock:


and a raft full of red Tiny Chiefs which are probably just as bad as the bumbles.

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Wed 13, 2011 6:18 pm 
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http://shop.ebay.com/i.html?_from=R40&_ ... Categories
you can paint all your other caps to look like bumble bees and sell those too :shock:


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Wed 13, 2011 7:17 pm 
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Quote:
you can paint all your other caps to look like bumble bees and sell those too


Now that is a great idea, anything to help the audiofools to spend money :shock:


Quote:
Carl, I never noticed a deafness on 10 with any of the SX-101As I've had. My standard weak signal at home was a 10M beacon in Baltimore on 28.297 - if it could hear that, it was about .5 uV sensitivity, and none ever failed to receive it fine.


John, mine is nowhere near many of my sets on 10M for AM sensitivity. In the 60's I refurbed several that were trade-ins while I was moonlighting for a couple of dealers and noticed the same.
The biggest eye opener was a friend, K1SLZ, who had one (dont remember which version but didnt have the VHF scales). He wanted to downsize from the CE-100V/SX-101/HT-33B to something smaller and bought the Drake 4 Line and a NCL-2000. At one point he had some problem with the 100V and I loaned him a NCX-5/NCXA while awaiting parts. An A:B comparison with the 101 was night and day, even on 15M for SSB/CW. Granted the NCX-5 has 2 RF and 3 IF stages plus a great AGC but there were only a few years between them. About 3 years later he went with a NCX-5MK2/NCXA/VX-501 and used them and the NCL-2000 until he died about 10 years ago.

He offered the 101 to me for $50 but he knew I wouldnt budge! Id just bought the 74A4, hadnt done all the mods yet and was still suffering with a POS Drake 2B.
Then I bought that 100V and it and the 75A4 is about 10' away as I type.

Carl


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Wed 13, 2011 9:33 pm 
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yeah paint the Tiny Chiefs to look like Bumble Bees and sell them on eBay. just as good. "creamy sound"
black spray paint. color stripes and youre done :shock:


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Wed 13, 2011 11:10 pm 
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John,

You were right, the first L.O. was dead. The .o47 did help the distortion a bit as well. Distortion still seems high but that's for later, want to see how a general alignment goes first, then start on the details. I'm not one to do a complete replacement of caps or resistors, but prefer instead to just replace the defective components. Keeps the trouble shooting skills sharp, and costs less. :wink:

Need to remove the dial bezel so I can strip and repaint it, looks like someone used an acid brush and thick old paint on it. The meter glass is also dirty inside and out, I didn't look at the meter to closely yet, but I'm hoping its easy to open up.

Then need to strip, do a little body work, and repaint the cabinet.

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Thu 14, 2011 2:00 am 
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Removing the .047 cap will kill the noise limiter. I'm thinking of using a DPDT switch to replace
the original SPST Hallicrafters part so it will put the cap back in the circuit when the NL is turned on.
Still have to verify that it will fit and that I can find a bat handle that looks like the original.

Pete

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Thu 14, 2011 3:24 am 
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Pete,

Having 160 coverage was one of the reasons I bought this particular receiver. Sure like the later knobs though.

I think you're right, and maybe the solution is to replace all the switches, If a pleasing bat can be found, then THOSE are shiny.

Read the entire manual this afternoon and was pleasantly surprised to find that after I remove the knobs, I only need to remove the nuts on the toggle switches, fone jack, and the four panel screws, to pull of the front panel. That's a lot less work than removing the nuts on ALL the controls.

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Last edited by Mikeinkcmo on Jul Thu 14, 2011 11:23 am, edited 2 times in total.

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Thu 14, 2011 3:28 am 
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Mike

My SX-101A was a local find, about 3 miles from my home! Came with a
B&W-5100 (a real boatanchor!) Front panel was rusted and damaged,
so I found a replacement. Be very careful with the glass dial scale, I've
seen them go for 100 bucks on ePay :shock: Mine is in the bottom of the
sock drawer in my bedroom dresser so it will be safe until I put the set back
together, LOL.

Pete

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Thu 14, 2011 3:37 am 
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Be sure to bring the entire sock drawer to the bench when the time comes. :wink:

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Thu 14, 2011 4:58 am 
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Location: Mt. Airy, Maryland
Peter Bertini wrote:
Removing the .047 cap will kill the noise limiter. I'm thinking of using a DPDT switch to replace
the original SPST Hallicrafters part so it will put the cap back in the circuit when the NL is turned on.
Still have to verify that it will fit and that I can find a bat handle that looks like the original.

Pete


Indeed, I forgot to mention that although IMHO the noise limiter is pretty worthless unless you encounter sharp pulse noise.

Getting rid of that .047 gives decent AM detector distortion performance to about 85% modulation index as opposed to about 60% before. I did some other mods on one I had, as i recall the audio gets routed thru the product detector when it's in AM mode and a few jumpers on the mode switch cured that, improving audio distortion further.


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 Post subject: Re: Got a new toy today.
PostPosted: Jul Mon 18, 2011 12:20 am 
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A little putty and paint, Then it is what it ain't.

Stripped the bezel casting and painted with auto store wrinkle black.
Image
I set it on a trash can in the sun for a couple hours to heat up, sprayed it, and came back 3 hours later and I'm impressed how nice it came out. At sundown, I set it in the garage over night. Opened the S meter up and cleaned both sides of the meter glass, spent maybe half an hour, with the heat of the soldering iron and took a lot of the warp out of the plastic meter scale. I remember that plastic from 40 or 50 years ago, and its very temp sensitive. A little too much heat and ITS HISTORY. Now the needle doesn't stick at about S5 or below.

Set the controls per the alignment preamble, fired it up and couldn't get a signal through it no matter what. Finally, after about 10 minutes of poking around, I discovered that, whom ever re-installed the standby switch years ago, installed it up side down. AGGRRRRGHHH!!!

It instantly worked fine, 10db S+N/N sens for 30% AM is between 0.4 and 0.7uV for from 1.9 - 28 Mc. Don't see a specification anywhere for claimed sensitivity, but the measured sens doesn't seem bad at all. Didn't do a MDS test or any high level tests. Only thing I've done so far is replace the 12BY7 first L.O. tube.

I'll let it "burn in" for the next few days while I work on the cabinet. Man, them switches still look UGLY.

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Last edited by Mikeinkcmo on Jul Mon 18, 2011 2:28 am, edited 2 times in total.

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 Post subject: Re: Got a new toy today.
PostPosted: Jul Mon 18, 2011 12:23 am 
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Looks purty. But, it looked purty in the box. What did you do to it?
Share a bit... :mrgreen: :mrgreen:

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