Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Oct Wed 27, 2021 2:22 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 59 posts ]  Go to page Previous  1, 2, 3
Author Message
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Thu 12, 2021 1:59 pm 
Member
User avatar

Joined: Oct Thu 04, 2018 2:11 pm
Posts: 825
Location: Suburban Chicago
Cosmetically your SX16/17 appears to be a 17 at a glance because it does have two toggle switches where the 16 has only one. However there does not appear to be any labeling for the second switch so BobE's speculation is plausible. The 17 has that switch labeled so yours could be a modified 16. The dead giveaway is to count the tubes. The 17 has 13, the 16 has 11. I only see 11 in your photo but two more could be hidden.

At a glance the SX-18 appears to have a bandspread dial and an S meter but Dachis assures us that it has no S meter. Thus the socket on the back for one. I haven't looked a your photos closely yet and the one in the Dachis book is too low in resolution to tell but I assume that the second auxiliary dial is either a second bandspread dial or possibly associated with the image rejection circuit that Dachis mentions. That feature makes the 18 interesting to me and I would be tempted to restore it rather than to part it out but your radio, your choice!


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Thu 12, 2021 9:32 pm 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
I just checked, and counted the tubes - 11, so it's a SX16, and in clean condition. I will not part this out for a xfmr that I will eventually find.

Frank


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Fri 13, 2021 5:30 pm 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
khutch wrote:
Cosmetically your SX16/17 appears to be a 17 at a glance because it does have two toggle switches where the 16 has only one. However there does not appear to be any labeling for the second switch so BobE's speculation is plausible. The 17 has that switch labeled so yours could be a modified 16. The dead giveaway is to count the tubes. The 17 has 13, the 16 has 11. I only see 11 in your photo but two more could be hidden.

At a glance the SX-18 appears to have a bandspread dial and an S meter but Dachis assures us that it has no S meter. Thus the socket on the back for one. I haven't looked a your photos closely yet and the one in the Dachis book is too low in resolution to tell but I assume that the second auxiliary dial is either a second bandspread dial or possibly associated with the image rejection circuit that Dachis mentions. That feature makes the 18 interesting to me and I would be tempted to restore it rather than to part it out but your radio, your choice!


Excuse me, but who is Dachis?

Thanks, Frank


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Fri 13, 2021 9:28 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3779
Location: Seattle WA US
Frank-
Chuck Dachis is a well known collector, and author of "Radios by Hallicrafters"

GOTO https://www.amazon.com/Radios-Hallicraf ... 0764308076

-Chuck K7MCG


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Fri 13, 2021 11:13 pm 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Oh! Interesting!

Thank you


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Sat 21, 2021 3:39 am 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
I've been side tracked for awhile. Now back on this project, it's time for troubleshooting.

Receiver is basically back together electrically and I have applied power through my isolation xfmr, variac and dim bulb.

All tube filaments are lit.

Bringing up voltage slowly while monitoring B+ and AC on pwr xfmr primary.

B+ starts to build off when AC is at approx. 40 vac, then quickly as I approach 75 vac and levels off at approx. 115 vac, with a final value of 340 vdc. on the 1st filter cap and 320 vdc on the 2nd filter cap.

Checking ac ripple and I'm surprised to read 35 vrms at 1st filter cap. Something is wrong! I connect the speaker at this point and get blasted by a loud hum! Quickly disconnect speaker and power down.

Check dc power section wiring - I find a connection which I forgot to solder - ground end of second filter cap. I correct this and power up again.

When the speaker is re-connected there is very little hum. I check ac ripple on DC. I measure approx. 35 mv. That seems to have corrected the high ripple voltage.

At this point I notice that the two 15k divider resistors are running very hot. I power off. I don't have a convenient way to measure the temperature of these resistors, but I can't leave my finger on them with out burning them. They are rated 2 watts. I decide to double the resistor rating to 4 watts. I remove the 15k resistors and replace each of them with two parallel 30k resistors giving me 15k but at 4 watts. Now, that's better. They get warm, but not hot!

At this point, I have rated B+, but the radio is deaf.
Start playing with the audio gain (volume control), 500k pot sounds scratchy. I do the soldering iron trick and touch it to the volume control wiper. Something is weird. When turning the pot clockwise, the noise gets quieter and when turned counter clockwise the sound gets louder. This area of the radio is as I received it. So, is the volume control pot wired backwards?





However, it appears that the 1st and 2nd audio stages are functional.



Please comment.


Attachments:
audio.jpg
audio.jpg [ 246.46 KiB | Viewed 1033 times ]
Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Tue 24, 2021 1:53 am 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
Hello all!

At this point, I'm measuring/recording tube voltages. I have all but three tubes to check, V1 , V2 and V3. These tubes are not easily accessible from the bottom of the chassis. I ordered a tube socket extender with test points and hope to have it later this week.

Question, did Hallicrafters publish tube voltages? I can't find anything in the SX-25 manual or from J. Riders pubs. When I did the S20R and S-38 the tube voltages and resistances were available in the manuals and helped to narrow down problems.

If someone on this forum is currently working on or has completed restoring an SX-25 , an would be willing to share tube voltages I would be grateful.

I do have another question regarding the variable caps for main tuning and band spread. In the manual these caps are listed as:

C1, Maini Tuning Gang
C2, 2 PL. Bd. Spr. Sec.
C3, 5 PL. Bd. Spr. Sec.

what do the '2PL' and '5PL' designate ?



Best regards, Frank


Attachments:
tuning caps-1.jpg
tuning caps-1.jpg [ 55.82 KiB | Viewed 984 times ]
tuning caps.jpg
tuning caps.jpg [ 499.33 KiB | Viewed 984 times ]
Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Thu 26, 2021 2:27 pm 
Member
User avatar

Joined: Oct Thu 04, 2018 2:11 pm
Posts: 825
Location: Suburban Chicago
I am tempted to think that 2 PL means the two plate section of the bandspread and 5 PL means the 5 plate section. However from the photos that I see it is not obvious that there would be a 5 plate section. It looks like the one section could have 1 or 2 plates on the stator but the other looks like it would be 4 plates, or 3. I'm at work, I can't dig mine out and look at it right now. Tracing out the circuit should tell you which is which.

There are some voltage charts in the manuals on BAMA. Hallicrafters did publish them.

I don't know about the volume control other than that nothing that either Hallicrafters or previous owners did would surprise me! Hallicrafters at least did some fine engineering work but when it came to putting it into the factory the results can vary somewhat. Generally good but not always.


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Fri 27, 2021 12:39 pm 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
khutch wrote:
I am tempted to think that 2 PL means the two plate section of the bandspread and 5 PL means the 5 plate section. However from the photos that I see it is not obvious that there would be a 5 plate section. It looks like the one section could have 1 or 2 plates on the stator but the other looks like it would be 4 plates, or 3. I'm at work, I can't dig mine out and look at it right now. Tracing out the circuit should tell you which is which.

I'm still a bit confused by these variable caps. My problem is I don't understand how
the physical capacitor details are depicted in the schematic. I plan to shoot some detailed pics so I can ask better questions.


There are some voltage charts in the manuals on BAMA. Hallicrafters did publish them.

Found them - thanks :D

I don't know about the volume control other than that nothing that either Hallicrafters or previous owners did would surprise me! Hallicrafters at least did some fine engineering work but when it came to putting it into the factory the results can vary somewhat. Generally good but not always.

It was me. I must have reversed the start and end terminals during re-cap. I re- reversed them and it is now as it should be.





Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Fri 27, 2021 1:52 pm 
Member
User avatar

Joined: Oct Thu 04, 2018 2:11 pm
Posts: 825
Location: Suburban Chicago
I dug mine out again last night and looked at the bandspread tuning cap. It is comprised of two caps joined by a common shaft and each of the two caps is divided into two sections, one has three moveable plates, the other has one. The three moveable plates mesh with two (a number I did not consider previously!) fixed plates so five total and that is undoubtedly what the 5 PL is referring to, C3. I actually could not see how many plates the one moveable plate meshed with but I am guessing it is one for two total and that is the 2 PL section, C2. Tracing the circuit out should confirm this since C2 and C3 connect to different places.

It is always a bit difficult deciphering these old schematics. They are loaded with terms and abbreviations of terms that have gone obsolete in the years since. Back then everyone would have just known what they referred to. It was tribal knowledge. That tribe has long since died out and we are left on our own, like archeologists trying to read some dead language. And then in some cases we discover that the terms were not even common to the industry tribe, but were dialects of the Hallicrafters tribe, the National tribe, the Zenith tribe, ....

It's all part of the fun!


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Sat 28, 2021 12:48 am 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
khutch wrote:
I dug mine out again last night and looked at the bandspread tuning cap. It is comprised of two caps joined by a common shaft and each of the two caps is divided into two sections, one has three moveable plates, the other has one. The three moveable plates mesh with two (a number I did not consider previously!) fixed plates so five total and that is undoubtedly what the 5 PL is referring to, C3. I actually could not see how many plates the one moveable plate meshed with but I am guessing it is one for two total and that is the 2 PL section, C2. Tracing the circuit out should confirm this since C2 and C3 connect to different places.

It is always a bit difficult deciphering these old schematics. They are loaded with terms and abbreviations of terms that have gone obsolete in the years since. Back then everyone would have just known what they referred to. It was tribal knowledge. That tribe has long since died out and we are left on our own, like archeologists trying to read some dead language. And then in some cases we discover that the terms were not even common to the industry tribe, but were dialects of the Hallicrafters tribe, the National tribe, the Zenith tribe, ....

It's all part of the fun!


The reason for my concern about C1,2,3, is that I removed them to better clean de-gunk the chassis.
I'm concerned about whether or not I reconnected them properly.
Here are the pics I took today.

The 1st photo looking down shows the band spread on the left outside and the main tuning on the right inside.

Band spread consists of caps C2 and C3 with two separate units connected by a coupling. The rear unit has two C2 sections and two C3 sections.
This is duplicated in the forward unit, two C2's and two C3's.

C1, the main tuning cap also consists of two units connected by a coupling. There are two sections of C1 in the rear and two in the front.

The next two photos show the caps from the side and it is possible to count the number of plates in the rotor and stator of each cap.

So based on these close up photos, are your caps identical?
Is the nomenclature , i.e., 2PL, 5PL more obvious?

Thanks for your interest

Frank


Attachments:
Variable Caps ID -TOP.jpg
Variable Caps ID -TOP.jpg [ 378.41 KiB | Viewed 886 times ]
Variable Caps ID BS.jpg
Variable Caps ID BS.jpg [ 572.54 KiB | Viewed 886 times ]
Variable Caps ID MAIN.jpg
Variable Caps ID MAIN.jpg [ 531.53 KiB | Viewed 886 times ]
Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Sat 28, 2021 9:16 pm 
Member
User avatar

Joined: Oct Thu 04, 2018 2:11 pm
Posts: 825
Location: Suburban Chicago
I just spent some quality time with my SX-25 cradled lovingly in my lap. You cannot trace the circuit out on yours because it is disassembled. It is difficult to trace mine because it is fully assembled. If I had the chassis out of the housing it might be easier. That would take more time than I have this afternoon and would risk losing parts. But even so I am certain that you have the sections of the tuning caps identified correctly. Each section of C2 should be tied to the corresponding section of C1 and then to the corresponding section of the bandswitch common. Each section of C3 goes to three lugs on the corresponding section of the bandswitch. All three caps are in parallel on three of the bands but only C1 and C2 are used on the others.


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Sat 28, 2021 10:54 pm 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
khutch wrote:
I just spent some quality time with my SX-25 cradled lovingly in my lap. .


khutch: You must have a very sturdy lap! :shock:

Thanks, Frank


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Sun 29, 2021 1:36 am 
Member
User avatar

Joined: Oct Thu 04, 2018 2:11 pm
Posts: 825
Location: Suburban Chicago
The odd thing is that I was trying very hard to verify visually that your capacitor IDs were correct and it was basically impossible other than by looking at the plates as they mesh the 2PL and 5PL designations had to be as you marked them. Then sometime after lunch it hit me that, DUH, there should be continuity between C1 and C2 all the time but only on some bands between C1 and C3. So, just now an Ohmmeter easily told me what a visual inspection would not do with the degree of certainty that I hoped to achieve. The markings that you have in your photos are correct.

But at least I got some quality time with my SX-25 and I assured her that retirement is coming. She will get her chance to sing again soon enough!

Enjoy yours. I may have said this here before but my SX-11 continues to impress and delight me. Depending on how you count them the SX-25 is perhaps 3 generations more advanced, it has to be a pretty nice radio!


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Aug Sun 29, 2021 1:50 am 
Member

Joined: Jan Tue 10, 2012 8:39 am
Posts: 2820
The SX-25 was a poor man's SX-28. I used a 25 for many years in my ham station. At one point I was tempted to replace it with an NC-173 but didn't do it.

Recently I repaired a friend's SX-25 and it brought back nice memories.


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Sep Mon 20, 2021 10:17 am 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
bob91343 wrote:
The SX-25 was a poor man's SX-28. I used a 25 for many years in my ham station. At one point I was tempted to replace it with an NC-173 but didn't do it.

Recently I repaired a friend's SX-25 and it brought back nice memories.


Bob, your friend is fortunate to have your help! :D

I have been distracted by some other issues, but this past week I did make some positive progress with this receiver. I'm now receiving stations on band 1 and 3. Band 2 and 4 are very quiet almost silent. :cry: I not sure how to proceed at this point.
Do you have any suggestions?

Thanks, Frank


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Sep Thu 23, 2021 4:11 pm 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
BUMP! :)


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Sep Wed 29, 2021 4:32 pm 
Member

Joined: Oct Sun 12, 2014 1:02 am
Posts: 346
Location: SE PA 19335
angelfj1 wrote:
BUMP! :)


I haven't received any response on this topic. To follow this SX-25 restoration, you may want to go here:

viewtopic.php?f=5&t=402626

Regards, Frank


Top
 Profile  
 
 Post subject: Re: Hallicrafters SX-25 restoration
PostPosted: Oct Sun 03, 2021 6:14 am 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3050
Location: N. Vancouver B.C. Canada
Please confine discussion to one thread.

viewtopic.php?f=5&t=402626


Top
 Profile  
 
Post New Topic Post Reply  [ 59 posts ]  Moderator: Sandy Go to page Previous  1, 2, 3

All times are UTC [ DST ]


Who is online

Users browsing this forum: hipcheck50 and 16 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB