Randy,

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I’ve been working on a SX-110, which uses the same type of instruction, and it’s confusing and seems counter-intuitive for peaking the first IF transformer.? Once you’ve identified the crystal frequency, you want to make sure that adjustment U is tuned for the center of the DIP you found – in other words, a MINIMUM of the beat note at the IF frequency.? At that point, the audio note will be much lower, and you’ll hear much more of a “swishing” sound than the beat note.? If you don’t find it, then you turn adjustment U a little bit one way or the other to try to bring the transformer into the range of the crystal frequency.

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To find the crystal frequency, I connected a VTVM to the 500 ohm speaker output and put my signal generator into a slow sweep between 450 and 460 KHz.? Watching the VTVM, I found a beat note dip on the slope of one of the passes – that got me into the “ballpark”.? I then stopped the sweep and set the generator for the approximate frequency where the dip was found, and then began manually adjusting the generator frequency in very small steps.? Once located (in my case, it was 453.48 KHz), I “peaked” the transformer for “minimum” beat note and maximum swishing sound.?

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Honestly, I believe there are easier ways to find the actual crystal frequency.? The instruction in the manual is too much voodoo for my taste.? My SX-110 is a bit of a fun test radio, and one thing on my agenda (for today, in fact) was to simply discover the crystal frequency by running the signal generator through it and monitoring for a peak on the oscilloscope.? The crystal will have maximum output at its resonant frequency.? Then, I’ll try peaking up the 1^st IF using that frequency, using a modulated signal and with the BFO turned off.

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73 – Steve, KW4H

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Hi Richard ?and friends too

I don’t know where they reside other than somewhere in the clouds. ?I just put “qst 1946” into google and that’s what I got …Oct came first and amazing there was the 42. Just lucky for once, or google knew I was going to look inside for a Halli 42 ?due to a flurry of previous requests

I did not look in detail in Dec issue ; Ilooked only about july to dec 46? ,, no doubt there is more in 47 but if found? what I wanted

The QST early pics have the R-42 , not the pm-23 that somebody Steve? Said was in radio news.

I thought QST was part of ARRL and ?i almost signed up to ARRL, a while back but they demanded to know more than the government and ?all the banks and the depth of my pants pockets ! ?…So I hit the top right X

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I will sneak this in here, but my understanding is that it receives AM , and CW all the way to the top, leaving a question, I guess a mode switch must be able to direct 88.1 Mc to either 10.7 Mc fm or 455 kc AM/cw ..dunno yet

Don VA3DRL

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Steve; and dedicated followers; I see no indication of variations or changes to the 42 in MY second edition Ostermans or in MY Dachis 1996 printing.

They managed to find the later revision info to list for the receiver tube functions.

I did see that FM ?went from 27 to 110 MHz [but ?I’ll bet the dial is in “Mcees”] allowing the SX-42 to do old and new FM bands

Seems to me I read somewhere about the 6^th band but? my take was that by production time, there were 6 bands so that was fixed.

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I just ran into the June 47 service bulletin on BAMA and on the ?first page under TUBE TYPES AND FUNCTIONS, it says for the first 7h7 ?“1^st f-m limiter amplifier” ?, the other is? “2^nd f-m limiter-amplifier” ???but the schematic strips the “f-m” and the “amplifier” leaving only “limiter” Old or not there should be a hint here.

Richard’s comment just arrived now, as to first produced year, I see both Dachis and Osterman showing 1947, and the first manual I have seen says January 1947 at the top. What I have seen on BAMA information has no 1946 dates, so I looked in QST and near the top found Halli adds:

Sept 46 and before see s-38 and s-40 no sx -42 then

Oct 46 ..Sx 42 first add ?I found in qst ?coming soon? look at the first simple sketches

???

nov 46? says first reviews

???

dec 46? first indication that it is/WILL BE ?is for sale? ..seems to be available

???

so other than the early test units it must have been 1947 before any consumer units ?went out the door, but it is close.

We can wonder if any of those 1946 early units are around ?

Seems we are off-topic again a bit

Don VA3DRL

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Per the Osterman book, the SX-42 was on the market from 1947 – 1950.? However, information on another site shows that it was advertised as far back as the December ’46 issue of Radio News (see attached).? AND – looking at the 1946 advertisement, the advertised frequency range was 540 kc to 110 MHz!? Therefore, my hypothesis was entirely incorrect.? Disclaimer:? I was born in ’59 and didn’t get into SWL’ing until I was about 12 years old – so I rely on online sources for historical information.? The site that stated that Hallicrafters added the higher frequency range later wasn’t exactly correct.? Anyway, Osterman states that there were circuit changes during the life of the SX-42.? Have a look at this site:

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73 – Steve, KW4H

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On the SX-42:? Osterman’s book indicates that there were several circuit changes during the production years of this model.? One of the back stories appears to be what happened with FM radio.? From 1936-46, FM was in the 42 – 50 Mhz band.? However, the FCC required FM stations to move to the new frequencies of 88 – 108 MHz by 1948.? In response, Hallicrafters added a sixth band, to bring the coverage up to 110 MHz.? What’s really confusing is that the model number stayed exactly the same despite all the circuit changes.

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73 – Steve, KW4H

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Jacques; Holy Moly! as we used to say, no wonder we? are in no-mans’ land.

Continuing the SX-42 diversion…I saw some of the detailed changes sheets on the BAMA site ?too, and they seem to address much of this.

It seems clear that at some point there were significant changes beginning at the secondary of the 3^rd IF transformer and ongoing, and the major rev must be adding that switch so that both the AM and FM go thru the first 7H7, whatever it is really doing.

Wonder why the change/changes?? Makes one think the original circuit did not have enough amplification on AM. ??

I am still trying to make sense of the circuit; is ?the 7H7 really amplifying or what?

Getting back to Sterves Original question about why one tube, not the other: One wonders Why use a Loctal when most are octals? The S-47 uses a 6SG7 in the same spot? but is called ??“FM 3^RD IF AMP –AM DET” and it is produced at the same time.

How is your band switch doing?

Don VA3DRL

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Jacques; Holy Moly! as we used to say, no wonder we? are in no-mans’ land.

Continuing the SX-42 diversion…I saw some of the detailed changes sheets on the BAMA site ?too, and they seem to address much of this.

It seems clear that at some point there were significant changes beginning at the secondary of the 3^rd IF transformer and ongoing, and the major rev must be adding that switch so that both the AM and FM go thru the first 7H7, whatever it is really doing.

Wonder why the change/changes?? Makes one think the original circuit did not have enough amplification on AM. ??

I am still trying to make sense of the circuit; is ?the 7H7 really amplifying or what?

Getting back to Sterves Original question about why one tube, not the other: One wonders Why use a Loctal when most are octals? The S-47 uses a 6SG7 in the same spot? but is called ??“FM 3^RD IF AMP –AM DET” and it is produced at the same time.

How is your band switch doing?

Don VA3DRL

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Hi Don,

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The different produced versions of the SX-42 made me scratch my head big time…

Let’s say that in the first versions (according to the schematic 89D210) the first 7H7 is identified as a “1^st 濒颈尘颈迟别谤”.

Probably because it is used only for the 10.7 MHz IF signal and then feeds the 2^nd 7H7 tube identified as the “2^nd limiter and 10.7 MHz AM detector”.

The 455 kHz signal from the 3^rd IF transformer is not coupled to the 1^st 7H7 but applied to half of a 6H6 used as a detector, the other half of the same tube supporting the Noise Limiter function.

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In the late production versions (according to the 89D257 schematic) both the 455 kHz and 10.7 MHz signals are applied to the first 7H7 tube grid, and it’s designation was changed to “3^rd 滨贵”.

Both 455 kHz and 10.7 MHz AM signals are then “detected” by the second 7H7 tube (control grid to cathode) and the right part of the 6H6, used as a detector in the first versions, is completely disconnected.

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And A LOT of components values and circuitry topology changed between the first and the last SX-42 made.

The one I restored last spring was something of a mix between the first and the last versions already (stamped May 12, 1947) and was more or less conform to the XXXX production run, so I decided to rebuild it to be compliant to the schematic 89D257E.

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Let’s figure here that there was 20 engineering changes applied successively to the production runs X, XX, XXX, XXXX and 1, updating the related schematics from 89D210 to 89D210K.

Then the 89D257 come, with more engineering changes creating versions from A to G.

The 89D257F required a change to the SW 1 (the Band switch), sections K and KK, and this is why I had not been able to implement this one.

But the Rev. G change, which added a 6.8 ohms resistor (R108) in series with the 6H6 noise limiter heater was doable.

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At the end, I do not know if my own “version” of the SX-42 work better (or worse) than any other…

But, at least, it works on all bands and modes !

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Jacques ?and the gang

Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp?

don

I have a suspicion that Hallicrafters, seeking their necessary profits, sought to design the best receivers they could using the most economical parts available to them, which may have varied from time to time.? Sales, marketing, and supply chain may have driven engineering, except on certain high-end models which may have been the personal pets of the engineers.

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73 – Steve, KW4H

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Jacques ?and the gang

Do you/we believe that an early version of the schematic was much the same as later versions BUT the old drawing was in error by calling the 7H7 a Limiter, when all the time it was an IF amp?

don

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Hi all,

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There is no 6SC7 in the SX-42.

The tubes used are (from the 89D257 latest schematic).

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1^st RF and 2^nd RF: 6AG5

Local Oscillator & Mixer: 7F8

1^st IF: 6SK7

2^nd IF: 6SG7

3^rd IF: 7H7

Limiter & AM detector: 7H7

Noise Limiter: 6H6

FM Discriminator: 6H6

BFO and S meter Amp: 7A4

Audio Inverter (phase splitter + driver): 6SL7

Audio Output: 2 x 6V6

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Scott, and ?Steve and the gang:

I think Steve clarified a mistake re the sx-110 , but he listed IF tubes for others ?and never said anything about my comment on the sx-42 .

he listed?? “SX-42 (1947-50) 6SK7, 6SG7”?

?my? ?1996 Dachis ?book and my ?Osterman? book says ?6SK7,? 6SC7, 7H7

I also said “Wonder if we have the same printing…”

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Now I wonder if ? my? ?1996 Dachis ?book and my ?Osterman[ second edition]? books ?are wrong ??about the 42

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For the 62 you mentioned ?,Osterman ?lists the same IF tubes as it lists for the 42, [6SK7,? 6SC7, 7H7] and also says the A version seems to be the same except for the speaker impedance,, BUT Dachis says? 6SK7?6SG7?6SG7?

I guess I must be off-track, and/or cant read these details so maybe somebody else can check these books?

Don VA3DRL

Depend on WHICH diagram…

I.E. which production version of the SX-42…

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The SX-42 schematic shows a 7H7 as the third IF, printed on the diagram.

73 – Steve, KW4H

The SX-42 schematic shows a 7H7 as the third IF, printed on the diagram.

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73 – Steve, KW4H

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Hello n7qmm25 and others

YES; Depending on font etc and goobers in printing C and G look quite similar

Let’s just say the C ?that I see in Dachis was a poor print of a G ?or my eyes are really tired so the second tube is REALLY a? 6SG7.

that agrees with most and just now I am reading ??James’s …sx-42 repair ?which lists?? ….edited
6SK7 - 1st IF
6SG7 - 2nd IF
6H6 - 2nd detector / Noise Limiter
7H7 (two) - FM Limiters? ………

Now ?I just looked at the BAMA schematic ?again and see that the 7H7’s are called “Limiters” [for the FM] and don’t see any sign of a “3^rd IF” …But …

Dachis ?says ?????“7H7 3^rd IF Amp “
Osterman ?says ?“7H7 IF Amp “

… Beginning not to believe the gurus.

Don VA3DRL?