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 Post subject: SX-42 Begun - At Last!
PostPosted: May Mon 29, 2017 9:17 pm 
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Having creatively procrastinated for the 2 years (almost exactly) that I've had possession of this feared and revered old beauty, I have finally begun its electrical restoration. I am about 1/3 of the way through the process of recapping it, and replacing many resistors as well.

Figuring I'd go for the low-hanging fruit first, I began in the power supply section and then moved physically vertically through the V10, V8, 7, 6, 5 circuits (Sam's designations). All was going well schematic-wise until I reached the V7, 6, 5 areas and began to see discrepancies between what I saw and what Sam's showed.

I will post a longer post later with issues that others may find helpful, but for purposes of this cry for schematic help, I offer the following information as to what I've done and believe I can do:

- I've probably read about every thread on ARF about this and related receivers (SX-43, 62, etc.)
- I have also read a number of non-ARF restoration pieces on this unit on the net
- I can read schematics without a problem and use my considerable stable of test eq. as needed
- I have read and used Chuck's (K7MCG) info to determine that my SX-42 is a "later" version calling for the 89D257 schematic, which as I understood to be what Sam's used and I'm using the latter.

- Here's the info on my SX:
S/N 93750 Number on chassis: 70E825 Number on back of front panel: 68D072

- Have downloaded BAMA copies of 89D257-G and -F but these are nearly unreadable using both irfanview and adobe. I was just able to make out that they both show 3 I.F stages, while my SX has only two.

In this latter respect, mine appears to match Sam's. However, the wiring from the selectivity switch more closely matches the 89D257 schematic connections to the 2nd I.F. (A6/A15) in Sam's.

This will only make sense to those familiar with the SX-42 and its schematic /production anomalies.

My reason for posting at this point is to request help obtaining readable copies of any schematics relevant to the "later" SX-42 production. I welcome any other input from anyone, up to and including, "Give it up, old man!" Color me discouraged for now, as without documentation I'm not sure I want to continue to put in the effort this will require.

I'm strongly commited to reviving her because she is what drew me back into the hobby 2 years ago, but the way forward isn't clear at the moment.

Thanks in advace for any help you can offer.

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Chuck K4CCW
Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


Last edited by WoodchuckTN on May Wed 31, 2017 3:21 pm, edited 1 time in total.

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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Mon 29, 2017 10:18 pm 
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Chuck,

When going through SX-42 and various flavors of SX-62 Halicrafters I basically restore to stock without paying much attention to the schematic so if you have an unmolested one then I would just replace capacitors part for part and check for out of value resistors as you go through it.

Don't rely too much on the identification of the two vs three IF stages since the schematics showing 3 IF stages has the the third stage also functioning mostly as a limiter as it is identified in the later schematics. The difference between an IF amplifier and a limiter is at what point the stage goes into hard clipping versus being a linear amplifier and with a limiter stage the goal is to have sufficient signal to drive it pretty quickly into hard clipping to strip off the amplitude modulation (primarily noise) from the FM signal.

Particularly for the SX-42 Hallicrafters couldn't decide whether this was a communications receiver doubling as a home entertainment receiver or vice versa and I think that drove some of the ongoing production changes.

So obviously I vote to go ahead and restore it :)

Rodger WQ9E


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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Mon 29, 2017 10:30 pm 
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Thanks, Rodger. I was hoping you'd be able to offer encouragement.

It has seen a number of not-so-skillful repairs, so I'll need to puzzle out some areas as I proceed.

I guess I'll have to rely on the brains here more than I'd figured on.

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Mon 29, 2017 10:48 pm 
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Chuck, the SX 42 has some inherent issues construction-wise which you should be aware of, but is still a great radio and worth the effort. My first 42 went fairly well so I undertook a second which was in even worse shape. Here are a few things I learned:

1.) The bandswitch is very densely packed and hard (impossible) to access. This really becomes a problem for the cathode resistors (R3 and R15) for the first and second RF amp tubes. They are smaller value resistors which are underneath the bandswitch and have invariably gone significantly high in value. In my second receiver, I clipped the wire to these and left them in place but substitute a new resistor at another location. They affect the RF gain if they are not as specified.
2.) Most of these receivers have had resistors replaced at some time in the past. I made the mistake of just changing out of spec resistors with the same value. This is fine as long as the first person did not make a mistake. In the case of my second receiver, there were several in the audio output that were wrong. Fortunately, this is not one of the areas in the schematic that had a lot of production changes and I was able to trace the schematic and fix what had been incorrectly done in the past and then repeated by me when I initially went through the radio.
3.) The trimmers for the lower band's antenna and RF coils are 2p to 6p ceramic variable capacitors. That is a total of 4p of range. some of mine had been replaced, I replaced a few more that were badly cracked. I do not like the adjustment I had for several bands, where the trimmers were basically set to minimum and did not peak. I fiddled with the main tuning capacitor position for hours, trying to find a setting where I could get all of the trimmers to at least find a peak in their range--but was unsuccessful--so even though the radio works on all bands--I am still not happy with the performance on the low bands.

My first SX 42 went so well, I embarked on the second which has taught me quite a bit more because of its problems. A radio that works well after changing a few parts is great--but a poor teacher.

Norm

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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Mon 29, 2017 10:54 pm 
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Take a look at Service hint #21 because a previous owner might have mistakenly tried to apply these to your receiver even though they should not have done so since it was produced after Service hint #21. This might give you a clue to some of the changes that were done by a previous owner.

As long as the band switch and tuning mechanism are in good shape nothing else should be a fatal flaw. I spent 3 hours in tall grass repairing a fence followed by a couple of hours on the tractor mowing so right now any non-physical work seems not so bad. I much prefer high voltage to mowing on a steep slope; several times today I had the tractor in 4WD with the steering wheel turned well off center to keep mowing in a straight line. Next year I think I may use some herbicide to do some of the mowing.

Rodger WQ9E


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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Tue 30, 2017 1:58 am 
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Norm,
thanks for the thorough reply - and for your previous restoration threads on the '42, which I have read cover-to-cover at least twice. In fact I've read enough about restoring this radio that would have scared off an sane person. :D I think one of the first articles I read was Phil's bandswitch saga. I think that's what motivated me to re-build my troubleshooting and repair skills before tackling the SX-42.

Rodger,
The idea of looking at Service Bulletin 21 is a good one, especially since there was a notebook tucked inside the case when I got it that contained that bulletin, a copy of the original manual, the Sam's folder copy, and several pages of a previous troubleshooter's notes.

I'm thankful both for the knowledge and skill of guys like you two, and for your willingness to take the time to help those of us who need it.

Rodger, I'm in a similar grounds keeping situation on our 5 acres here with hills, etc. I've had to exchange my Kubota tractor and Dixie Chopper for a more sedate -and probably safer for me- Cub Cadet. One must adapt as life's changes come along.

I just hope I haven't waited too long to get started on this SX-42. :D

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Tue 30, 2017 3:04 am 
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Chuck,

You haven't waited too long for the SX-42, like every other boat anchor restoration it will have it easy parts and perplexing parts but in the end it will all come together.

It was probably good that I didn't grow up on a farm because I would have a little more tractor skill but a lot less caution. I am using a Deere compact utility (33 horse model 955) that I bought in 1995 and it has served me well. It is small enough to be maneuverable and big enough to handle a field mower and loader while the 72" finish deck makes pretty fast work of the 5 acre property. As of today the engine hours just rolled over 800 so I expect the diesel engine has a lot more life in it. My 13 year old daughter will start doing some of the safe stuff on level ground but even with the roll over protection bar there is no way I will let her get near the creek or the steep slope by the road. I did teach her how to operate the loader last year so she will know a lot more about it than I did at her age.

Keep us updated on the SX-42. I think Hallicrafters did a nice job with the styling and feature set of the SX-42 since it would have worked well both for the family ham and as a very good quality family entertainment receiver. Adding those features and style probably made it a much easier item to sell and they obviously sold a lot of them.

Rodger WQ9E


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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Tue 30, 2017 3:45 am 
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Just always keep,your wits about you with the tractor as there are plenty of ways to hurt yourself. I had a couple of really scary incidents with mine, long before I ever gave it up, and while I still had the agility and strength to recover from my mistakes in judgment.

Now that I'm past my "threescore and ten", I would likely no longer be able to get myself out of trouble as I did then. Thus, time to adapt to change and go back to the slower, less-powerful riding mower and hire others to do the parts I ought no longer to be messing with.

As for the SX-42, it is special to me because it was a life-changer for me. Researching its value for a nephew so he could possibly sell it, I became totally intrigued by it, and by the test equipment of the same vintage that I encountered in my research. I had decades before abandoned electronics as a hobby in favor of woodworking, as I was making my living in electronics and needed a hobby that was a diversion, not a continuation.

Well, the SX-42 showed up just as arthritis was beginning to make woodworking both painful and even unsafe. My nephew made me a gift of the SX and before I knew what hit me, I began to accumulate vintage test equipment and boatanchors, building an electronics workshop in what had been a woodworking shop, and spending a lot of time reading the old classic vacuum tube texts to refresh my electronic skills.

Early in my SX research I discovered ARF and I've spent untold hours learning from the masters here. What a treasure have Alan and the contributors here at ARF created!

Sorry, that was a very long-winded way of telling you why this special radio is extra-special to me.

If you've made it this far, thanks for listening. I'll try to be more succinct in further chronicles of this project.

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Tue 30, 2017 6:36 pm 
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Chuck, Roger, and Norm,

I have been reading your posts on the SX-42 with great interest as I have one too, that has been waiting restoration for at least 10 years. It worked when it was given to me but I have not powered it up in almost as long. I am happy that I have put off the restoration for all these years given what I have been reading here. Mine came out of a local college physics department, where it was used mostly for time signals from WWV for experiments in the department. I suspect that it has had little, if any modifications done to it. Or so I was told at the time that I received it. I am going to put off, still further, any work on it until after some of these restoration threads are complete. (Perhaps, just procrastinating on my part). But I am glad I did. I am reading with great interest! But have nothing to offer in constructive comment. Best of luck to both Chuck and Norm.

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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Tue 30, 2017 7:00 pm 
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When re-capping, don't forget about the two line bypass caps under the bottom pan of the power transformer (if it uses one).

My SX-42 was my favorite bedside radio for many years. The FM band is a welcome feature at times and sounds great when working properly.

Dave


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 Post subject: Re: SX-42 Begun - At Last! Continue??
PostPosted: May Wed 31, 2017 2:55 pm 
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N9,
Thanks for weighing in. Now at least I won't go down as the longest procrastinator. :D
The search feature at the top left will bring up many good completed threads on the SX-42 which I have found very educational - and inspirational.

Dave,
I started with the power supply area, as I wanted to quickly get the nasty electrolytic kludge out of there. This area was kind of "low-hanging fruit" as well. My SX doesn't use the cover on the transformer and someone had installed huge 1600 volt paper caps for the line caps. Replacing them with modern safety caps right away have me much better accessibility to clean up other wiring messes in that area.

My plan is to install a 3-wire power cord, fuse, and in-rush thermistor when the other surgery is done.

I am excited to report that I discovered a very clear copy of schematic 89D257-D in my accumulated paperwork. Using a magnifying glass to check it against some of the areas surrounding the 2nd IF and limiter (or 3rd IF) I found that it appears to match what I have!

Tiring very quickly of the magnifying glass, I took the schematic to my wonderful little local print shop and paid a few bucks to have them blow it up 300% to about 24x36. I then used spray adhesive to mount it to cardboard like I've done with several other large restoration schematics. It makes the work much easier.

I'm also keeping a list of any anomalies to aid any later troubleshooting I may need to do.

Thanks to all for your interest and input. Now if someone can just come up with some magic for getting at those caps and resistors in the rf section that I'm saving for last. I've read several techniques but none of them sound like fun.

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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: May Wed 31, 2017 5:12 pm 
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Keep up the good work, I too have one that I have been procrastinating on. I had also hoped to gain knowledge and experience before I cracked it open. I always read the SX-42 threads on ARF and have also read a bunch online including Phils Bandswitch saga. Maybe next winter, lol.


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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: May Wed 31, 2017 6:12 pm 
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Thanks, K8...
Phil's article was one of the first that I read and it nearly scared me off. Not too much later, I read Primitiveradiogod's thread here on ARF and it made me think, "Well, if he can do the impossible, maybe I can do the difficult."

Actually, so far, the most difficult part was the identification of a useable schematic. However, I know the tuning mechanism and rf components are still lurking in the weeds - not to mention whatever else may pop up.

Meanwhile I'll try to focus on eating this elephant one bite at a time - with a little help and encouragment from my friends here.

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: Jun Mon 05, 2017 5:42 pm 
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Not sure if this belongs here, but I bought these online over the weekend in anticipation of the tight quarters in the RF section. Even though I'm just moving from the IF section into the audio section to its right, I have already used these Channellock 748 Long Reach End Cutter Pliers this morning. I believe they'll find a lot of use going forward.

They're not cheap, but there's nothing like having the right tool.
Attachment:
2017-06-05 11.16.07.jpg
2017-06-05 11.16.07.jpg [ 87.41 KiB | Viewed 2361 times ]

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: Jun Tue 06, 2017 3:49 am 
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You won't need it often, but when you do it is sure nice to have. I have the same tool and have used it once. It is worth the "price of admission "!!!

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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: Jun Tue 06, 2017 3:46 pm 
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You will also find a pair of very long reach miniature diagonal cutters will help because they can be angled in to places where the end snips won't fit. I have often used both types in tight chassis spots where the disassembly otherwise needed to reach a component provides far too great a chance of expensive collateral damage.

Completely removing the side cover over the L/C components for the top two ranges greatly improves access and also lets in much needed light while working on the front end. This cover MUST be back in place before you start alignment because it changes the stray capacitance in the circuit.

Rodger WQ9E


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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: Jun Tue 06, 2017 10:07 pm 
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Hi Rodger,

Do you mean like these?

Attachment:
2017-06-06 14.46.14.jpg
2017-06-06 14.46.14.jpg [ 45.47 KiB | Viewed 2281 times ]


I actually bought these last year some time based on a thread over in the Test Equipment Forum here, and in anticipation of this project as well as a Hickok 155 Traceometer rebuild coming up. The latter, like the SX-42 has a number of components sandwiched between the front panel and an internal shielded RF box.

I have already used these on the SX42 to replace a cap under the xtal filter area. I don't often work in tight places, but when I do... :D

As for the side panel you mention, are you talking about the smaller panel that attaches to the main side gusset, which in turn binds the chassis to the front panel? If so, that was missing on mine. I'll need to find or fabricate one for this one.

That will be one of the last things needed, so I'm kind of making a list of things like that which I'll need to locate.

Thanks form your help.

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: Jun Wed 07, 2017 4:15 pm 
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Hi Chuck,

Those cutters are exactly what I was describing.

I believe that the cover over the fifth and sixth band coils is the same for the SX-62 and SX-42 but I have never measured it. Perhaps someone who has a SX-62 out of its case could measure it but I would be astonished if they aren't the same. There were a lot more of the various SX-62 flavors sold so it would probably be easier to find one from a SX-62 parts unit.

Rodger WQ9E


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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: Jun Wed 07, 2017 4:53 pm 
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Thanks as always for your valuable input, Rodger.

I also meant to mention that those long-reach side cutters were actually purchased from a supplier of Bonsai gardening tools and are meant for snipping usage in that hobby. They are very well made and I believe are stainless steel of some type.

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: SX-42 Begun - At Last!
PostPosted: Jun Wed 07, 2017 5:19 pm 
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My hint for deep down in bandswitches (my SX-88!) is twofold!

Cuticle scissors! Go to Walgreens and buy a few cheap ones. They are great for
clipping wires deep down, and while they soon get too sprung to work, who cares they are so cheap.
I was able to cut surprisingly stiff cap and resistor leads.

Second ... get yourself a soldering gun and some number 8 to 12 bare copper wire. Places like Home Depot or Lowe's
have short pieces of it. Make yourself a very long tip out of the wire. You can bend this to get
way down in the weeds. I found some suitable thick (.5 to 1mm) wall PTFE Teflon tubing that I use
to make electrical/thermal insulation for the wires. Amazon has it.

I was able to replace a cathode resistor down in the darkest, deepest 1st RF stage.


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