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 Post subject: Hallicrafters SX-25 restoration
PostPosted: May Mon 31, 2021 11:51 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Just acquired an SX-25 and my plan is to restore it electrically. One of the first things I want to check is the power xfmr. It has 10 terminals which are labeled 1 - 10. I have at least two versions of the schematic, Hallicrafters and Riders and unfortunately terminal numbers are not shown. Although I could figure it out through testing, does someone have the windings and terminal assignments?

Thanks in advance!

Frank


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Mon 28, 2021 6:57 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
I never did get a response to my original post - kind of disappointing, so I figured it out my self. So for the benefit of others who need the power transformer terminal connection details see the attached schematic.

Frank


Attachments:
schematic - power-R1.jpg
schematic - power-R1.jpg [ 87.38 KiB | Viewed 2487 times ]
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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Mon 28, 2021 7:00 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
oops! I just noticed that terminal 10 and 6 voltage were omitted. They are approximately 350v - CT - 350V.

Frank


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Mon 28, 2021 7:05 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
I'll be ordering a replacement electrolytic filter cap for this restoration. Unfortunately, I damaged the original filter cap flange when removing the original cap. I did not realize that removing the flange wasn't necessary, so I removed it. it was riveted and soldered to the chassis. Does anyone know of a source for a replacement.

Thanks, Frank


Attachments:
Filter Cap -SX25-flange.jpg
Filter Cap -SX25-flange.jpg [ 236.36 KiB | Viewed 2486 times ]
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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Mon 28, 2021 7:21 pm 
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Joined: Jan Tue 10, 2012 8:39 am
Posts: 2815
That is what I call a mounting plate. They come in various sizes and I may have a few. They also come in steel or phenolic; I see yours is steel.

If you can send me a drawing or template I will see if I have one. An SASE into which I can stuff it if I find the right one.


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Mon 28, 2021 11:40 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Thanks bob91343!

Let me see if I can make a rough sketch and I'll post it here.

Frank


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Tue 29, 2021 12:16 am 
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Joined: Nov Sun 29, 2020 5:59 pm
Posts: 279
Location: Northeast Illinois 60188
If Bob doesn't have the style that you need, check here:

https://www.amplifiedparts.com/products ... rs=746a130

They also sell on eBay.

- Jim


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Tue 29, 2021 12:45 am 
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Joined: Mar Thu 04, 2010 3:09 am
Posts: 127
When I recap an old tube radio I leave the old cans in place for appearance and disconnect them under the chassis. There is plenty of room in an SX24 and 25 to hang the modern electrolytics under the chassis and I have done one of each. This method is inexpensive and works well. You could put the old one back in if you did not damage the base too badly.

Rich


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Tue 29, 2021 2:49 am 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Jim, Rich, many thanks for your suggestions. The Hayseed filter cap is expensive, so I think I will try to stuff the original one. Boy, they sure look cruddy inside, when you remove the paper/foil roll. Is that crystalized stuff toxic? If stuffing doesn't work out very well, I'll put the can back on top empty and add a terminal strip for new caps.

Best regards, Frank :D


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jun Tue 29, 2021 11:33 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Questions concerning tuning capacitor connections.

I removed the main tuning and bandspread caps to facilitate the cleaning and inspection of these. I see three types of connections, braided tinned copper between the stator and chassis at several points; insulated solid wire connections from rotor to underside via holes in the chassis, and the same but via bare solid copper wire. I understand the use of the braided conductor and insulated wire, but why the use of bare wire, which in some cases comes very close to the edge of the hole. When reconnecting, can I just use insulated wire or add heat shrink to avoid shorting out these connections?

Thanks, Frank


Attachments:
20210623_114412-R1.jpg
20210623_114412-R1.jpg [ 758.95 KiB | Viewed 2372 times ]
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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Thu 01, 2021 2:02 am 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Re-capping: I'm preparing to start the re-cap of this receiver. I need to make a decision regarding removal of the antenna and oscillator coils, along with the band switch. If you examine the photos below, you can see that access to three tubes and several wax-paper caps are obstructed by this structure. So, do I replace all of the easy to reach caps and hope that the radio comes back to life, or do I attempt to loosen the mounting of the coils and band switch enough so that I can replace those caps deep underneath and also evaluate the other components associated with the three tubes that are behind this structure.

Note: I'm a bit intimidated by the thought of removing the coils and band switch. Has anyone here done this with an SX-25 or similar receiver? Is anyone aware of any documentation regarding such a tedious process?

P.S. If you click on the photos and enlarge them you can see how some of the wax paper caps are deep underneath the coil and band switch structure, not to mention three of the vacuum tubes.

Thanks, Frank


Attachments:
20210529_094532.jpg
20210529_094532.jpg [ 198.52 KiB | Viewed 2315 times ]
File comment: Several wax paper caps and three tubes are behind this structure.
20210526_160853.jpg
20210526_160853.jpg [ 221.48 KiB | Viewed 2315 times ]
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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Thu 01, 2021 4:06 am 
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Joined: Jan Tue 10, 2012 8:39 am
Posts: 2815
Not a job for the faint hearted. I did some work on a similar area in a model S-20R and there were problems getting stuff where it was supposed to be. In particular, the bandswitch wafers had deteriorated with age and needed to have the right mechanical preloading to get them to make contact.


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Thu 01, 2021 4:18 am 
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Joined: Mar Thu 04, 2010 3:09 am
Posts: 127
With care I was able to replace every paper cap in both an SX24 and 25. I might have used a very small pencil iron but do not really remember.

Coils and switches can be verrrrry brittle and if you crack one you are done so I do not move them unless absolutely necessary. I have cracked the BFO coil in an SX42 and the wafer mode selector switch in an HW100. Did not really need the BFO in the SX42 so got over it. Found an HW100 switch for $5 and returned it to good function.

The 24 and 25 are pretty robust radios though so a little care will get you through. If you are really concerned about the caps under the switches let them be and hope they are ok. Some of them you can live with if only a little leaky. I did that in the SX42 and 62 in the RF section and they work fine.

The caps in the audio section do need to be replaced so get to those. Especially in the SX25 as there is an audio phase shift circuit and push pull 6V6 tubes. If any one of the caps around there is bad the audio will be badly distorted. The SX25 has wonderful audio that you will enjoy. I found an R42 speaker for it and it can rattle the windows!

Rich


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Thu 01, 2021 1:39 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Sounds like good advice!
Don't mess with those coils unless its the last resort

Frank


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Tue 13, 2021 4:46 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
I’ve made good progress with the re-capping. With a bit of patience and a new slim soldering iron, I actually replaced all of those wax=paper caps. Even the ones under the coils. I just started on replacing out of spec resistors. The 2W ones seem to be the worst. But now I found a new challenge – an unidentified 2W, 100 ohm resistor. Not shown in the component list or the schematic. This resistor does not look like a replacement made by a repairman or owner. It looks very original. Photo later if needed. I am using the Hallicrafters reference shown below. I have read about the agony that others have experienced due to multiple versions of other Halli receivers, so can anyone tell me if there are other versions of this SX-25, with alternative components, etc. I plan to proceed with replacing out of spec, identified resistors BUT I hope one of you can shed some light of this issue I have found.

Thanks in advance, Frank


Attachments:
SX-25 Opp Inst - cover page.jpg
SX-25 Opp Inst - cover page.jpg [ 446.87 KiB | Viewed 2060 times ]
resistor list.jpg
resistor list.jpg [ 323.31 KiB | Viewed 2060 times ]
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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Tue 13, 2021 4:48 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
see schematic


Attachments:
Hallicrafters Original Schematic - SX-25-R1.pdf [153.18 KiB]
Downloaded 82 times
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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Tue 13, 2021 5:58 pm 
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Joined: Apr Wed 01, 2020 7:22 pm
Posts: 333
Where is it connected in the ckt..?? A pic or two would be of great help too...!

73...Jordan


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Tue 13, 2021 6:17 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Thanks Jordan. I'll take a pic soon.

Frank


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Tue 13, 2021 7:37 pm 
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Joined: Oct Thu 04, 2018 2:11 pm
Posts: 821
Location: Suburban Chicago
angelfj1 wrote:
I have read about the agony that others have experienced due to multiple versions of other Halli receivers, so can anyone tell me if there are other versions of this SX-25, with alternative components, etc.


I won't be any direct help because while I have an SX-25 I have not started to work on it yet. I know what you are saying however. I've done an S-38 which is much simpler but there are (at least) two different versions of the BFO circuit even though it was only produced for about a year and the separate BFO requiring a sixth tube was dropped entirely in the follow on S-38A the next year. My current project is an SX-11 which is approaching completion. There were some minor deviations from the available documentation and then one major deviation that has been seen in at least one other example here on ARF. My radio has a switchable BW IF circuit like that seen on the SX-16 and -17 and in increasingly sophisticated form in many of the later higher end Hallicrafters models even into the 1960s. I have used the SX-16 schematic as a guide to work on that part of my -11 and that has worked well for me so far. I had to borrow part of the alignment procedure from the -16 as well.

It is all part of the challenge and joy of restoring a Hallicrafters!


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 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Jul Tue 13, 2021 7:46 pm 
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Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Here's a pic of the resistor in question.

Frank


Attachments:
unknown 2W, 100 ohm resistor.jpg
unknown 2W, 100 ohm resistor.jpg [ 622.14 KiB | Viewed 2033 times ]
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