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


It is currently Oct Sun 25, 2020 5:50 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 11 posts ] 
Author Message
 Post subject: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Tue 08, 2020 3:31 am 
Member

Joined: Apr Sat 27, 2019 3:30 am
Posts: 157
SO my Hallicrafters s-38 is almost completely finished now. A touch more of paint on one side and just the electrolytics and it'd be finished. Technically it's working fine now so I might hold off just a bit on the electrolytics since the originals don't seem to be giving me any trouble atm. With all that said though...One thing i'd like to do is use headphones on it. Problem is it uses two pin jacks that can't really be used with modern headphones. I don't really want to buy antique headphones, partly cuz the few I've seen don't look all that comfortable, but also simply because I've got a few really comfortable modern ones I don't really use much anymore for anything else.


Ideally I want to do this in a way without modifying the actual radio itself which is why I'm curious if there's a way to mod some current headphones in a way that would make work AND be safe to use. While I will be looking into other safety measures for this one (like a new polarized cord) eventually, since I know the only thing standing between me and a nasty shock are 4 rubber feet on the bottom, I still want to avoid modding it too much.


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Tue 08, 2020 4:28 am 
Member

Joined: May Tue 30, 2006 4:46 pm
Posts: 10199
Location: Santa Rosa, CA
You will likely need a matching transformer and a way to connect the "modern" phones, probably stereo, to serve as mono headphones. Modern phones are likely to be around 32 ohms. Don't know about your S-38, but guessing it was used with 2000 ohm phones.

http://makearadio.com/misc-stuff/t-725.php

Rich


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Tue 08, 2020 5:24 am 
Member

Joined: Jan Sat 25, 2020 5:23 am
Posts: 158
Location: Colorado Springs, CO 80917
There was another discussion of this same topic here:
https://www.antiqueradios.com/forums/vi ... 6&t=310418
and the statement was made:
"According to the S-38 manual, headphones in the impedance range of 50 to 5000 ohms are recommended. 4 or 8 ohm phones should work but the mismatch would probably result in reduced volume."

I note on the schematic & parts list that the audio output transformer is a 15 ohm secondary with a 3 ohm tap. The speaker is cited in parts list as a 3.2 ohm speaker & it connects to the 3 ohm transformer tap.

For headphones, there is a resistor, R-15 of 15 ohms, placed across the secondary and the headphones connect across (parallel with) R-15. So, any headphone impedance that in parallel with R-15 doesn't change the total from around 15 ohms much, should work.

To use low impedance cans (e.g., 4 to 32 ohms etc) one really should get a little transformer to transform the low impedance to something pretty high (e.g., 500 ohms or higher). A 500 ohm headphone load would only shift R-15 to about 14.6 ohms, unlikely to be any problem & anything higher is just better.


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Fri 11, 2020 4:19 am 
Member

Joined: Jan Tue 16, 2007 7:02 am
Posts: 3914
Location: Lexington, KY USA
Hook them up directly and see how they work. Just connect the L and R channels on the phones together.

If the results are OK, then you are done.

If the results are poor, then you can look for a fix.

Ted


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Thu 24, 2020 6:00 am 
Member

Joined: May Mon 25, 2020 7:37 pm
Posts: 237
Location: Boston, MA
Fair Radio Sales has some surplus military headsets (Korean War era) with impedance in the 300-600 ohm range. I bought a pair for my Atwater Kent Model 20 restoration. Prices were in the $12-$20 range, plus shipping.


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Fri 25, 2020 10:53 pm 
Member

Joined: Feb Wed 12, 2014 4:25 pm
Posts: 153
Location: Southeast Kans. - KA0HCP
https://www.radioshack.com/products/rad ... LeEALw_wcB

Radio Shack Audio Transformer 1k/500 to 8 Ohm. $4.00. A little bigger than a sugar cube. I used to buy these half a dozen at a time to keep in my parts box. YES, Radio Shack is still in business. BTW, price on this item hasn't gone up in 35 years! bill


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Fri 25, 2020 11:44 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 8690
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Keeta wrote:
I know the only thing standing between me and a nasty shock are 4 rubber feet on the bottom, I still want to avoid modding it too much.


Amazing ..... after all the discussions we've had about the need to "complete a circuit", this old wives tale is still making the rounds.

Have a look at the schematic. If it was mine, I'd simply wire an headphone jack into the wires going to the speaker so that the circuit is interrupted when the headphones are plugged in. Then either mount that jack on the rear cover or run the leads out thru' the back cover vent holes into a little box that the jack is mounted in.

And no ..... it's not a hot chassis. There's a capacitor between B- and chassis.


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Sat 26, 2020 6:03 pm 
Member

Joined: Apr Sat 27, 2019 3:30 am
Posts: 157
John Bartley wrote:
Keeta wrote:
I know the only thing standing between me and a nasty shock are 4 rubber feet on the bottom, I still want to avoid modding it too much.


Amazing ..... after all the discussions we've had about the need to "complete a circuit", this old wives tale is still making the rounds.

Have a look at the schematic. If it was mine, I'd simply wire an headphone jack into the wires going to the speaker so that the circuit is interrupted when the headphones are plugged in. Then either mount that jack on the rear cover or run the leads out thru' the back cover vent holes into a little box that the jack is mounted in.

And no ..... it's not a hot chassis. There's a capacitor between B- and chassis.

Does that still hold true for the s-38c model? I forgot to add the c to the end when i made that post.


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Sat 26, 2020 9:50 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 8690
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Keeta wrote:
Does that still hold true for the s-38c model? I forgot to add the c to the end when i made that post.


I am not going to answer that until you look at the schematics and tell us what YOU think.

Learning is always a good thing.

cheers


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Sun 27, 2020 2:20 am 
Member

Joined: Apr Sat 27, 2019 3:30 am
Posts: 157
a simple yes or no would have sufficed simply because I just got to work at the time and didn't really have time to go looking through a schematic. How's about learning not to be a smartass?

Considering that almost every place I looked up info on this radio listed it as a hot chassis one, from youtube channels of folks who restore radios all the time, to even a couple posts here, you can't fault me for assuming it was one.


Top
 Profile  
 
 Post subject: Re: Converting Normal headphones for my S-38 Hallicrafters?
PostPosted: Sep Sun 27, 2020 2:47 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 8690
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Keeta wrote:
a simple yes or no would have sufficed simply because I just got to work at the time and didn't really have time to go looking through a schematic. How's about learning not to be a smartass?


No smartass about it. You asked a question, but you didn't give us the correct info the first time, got a straight answer and then you expect us to do your checking for you the second time?? How about getting off "your" ass and doing your own homework?


Top
 Profile  
 
Post New Topic Post Reply  [ 11 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 14 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB