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


It is currently Jul Sun 21, 2019 2:03 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 22 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Wed 12, 2019 12:27 pm 
Member

Joined: Aug Sat 19, 2017 6:55 am
Posts: 52
Location: Glendale, AZ, USA
Hi.

I'm picking up one of these Thursday. I've already found a place that sells the re-cap kit. :o
But I am not having any luck so far finding a schematic for this. I had thought I found a place, but seems they don't go this new.

I'm new to this older radio restoration stuff. Is an isolation transformer the best way to go for safety, or are there other ways that are considered better these days?

I learned electronics with vacuum tubes my first year of high school electronics, but that was a LONG time ago. :oops:
Been a working tech for most of the last 30 years, but has been almost all newer surface mount type circuits. Looking forward to getting back into tube circuits.

Any help appreciated.

Thanks,
Russ


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Wed 12, 2019 2:57 pm 
Member
User avatar

Joined: Jan Mon 05, 2009 4:09 am
Posts: 1354
Location: Hudson, MA
Here you go:

https://www.radiomuseum.org/r/hallicraf ... sw500.html

_________________
Eddy


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Wed 12, 2019 3:57 pm 
Member

Joined: May Wed 06, 2009 7:01 pm
Posts: 826
http://bama.edebris.com/manuals/hallicra/sw500/ (in djvu format)

Schematic is same as Hallicrafters S-120
http://bama.edebris.com/manuals/hallicra/s120/ (in pdf format)

Isolation transformer recommended for safest approach. The only unique glitch in these sets is the R-20 "globar" voltage dependent resistor which slows the current rush in the filament string, increasing the life of the tubes and pilot lights.

-- Rich


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Wed 12, 2019 4:49 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
Replace all electrolytic caps and paper caps.

Also replace all carbon comp resistors.

The last bit is a personal preference of mine, but it can make a device more reliable over time.

Also the speaker itself to me doesn't sound too good for the size speaker it is. Just use whatever speaker you have laying around that is the same size and is 4-8 ohms and fairly efficient.

Once you have everything done, do an alignment.

I recently restored one for a friend of my dad's and I found an oval speaker which fit and made the radio sound so much better.

The radio itself should be ok to use without an isolation transformer, but if you would rather use one build it per this diagram.

Attachment:
transformer connections 2.jpg
transformer connections 2.jpg [ 25.85 KiB | Viewed 340 times ]


Attachment:
transformer connections 3.png
transformer connections 3.png [ 30.89 KiB | Viewed 340 times ]


Use a polarized plug on the radio with the wide blade being the neutral.

The .01uF capacitor should be a safety rated capacitor. The purpose for that capacitor is to provide a path to ground for RF as using the transformer breaks the path that is normally through the neutral of the radio's power cord and without a path to ground, reception will not be as good.

The 12uF film cap is there because for a 120Vac input to the transformer it outputs 126Vac under the light load most AC/DC radios draw and the capacitor reduces the voltage down to 120Vac.

You can simplify things by getting one of those outlets with built in switch.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Thu 13, 2019 10:00 am 
Member

Joined: Aug Sat 19, 2017 6:55 am
Posts: 52
Location: Glendale, AZ, USA
Thanks, all.

Might have to pay to join that radio museum site. Hate to be a leach. Was expecting to have to buy the schematic.

RE the outlet with a built in switch, is that just to turn power off when not in use, or is there some other purpose? I'm more worried about frying myself while poking around tuning and such, although having a quick way to kill the power isn't a bad thing.

ETA I just realized that those two diagrams are slightly different. Is one way better than the other?

Thanks, again.
Russ


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Thu 13, 2019 1:34 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
The switch serves to turn the power on and off. That way the isolation transformer is not on 24/7 and it saves wear and tear on the radio's power switch along with no longer having to remember where the volume control is set as it will not have to be moved anymore given an external switch turns the radio on and off.

Which you use depends on if you use a grounded cord to the outlet box or not. For safety if the box is metal use a grounded cord and ensure the box is grounded.

If using a plastic box a grounded cord is not necessary unless code requires a grounded cord be used when using a grounded outlet.

Also I didn't show a fuse, but a 500mA slow blow should be fine placed right before the power switch.

The fuse protects the radio and also protects the isolation transformer should someone try to plug anything into the outlet that draws over 500mA.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Thu 13, 2019 1:42 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7848
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
russosborne wrote:
Thanks, all.

Might have to pay to join that radio museum site. Hate to be a leach. Was expecting to have to buy the schematic.

RE the outlet with a built in switch, is that just to turn power off when not in use, or is there some other purpose? I'm more worried about frying myself while poking around tuning and such, although having a quick way to kill the power isn't a bad thing.

ETA I just realized that those two diagrams are slightly different. Is one way better than the other?

Thanks, again.
Russ



Russ,

All this hype about isolation and three wire plugs .... it's paranoia. Just do your radio restoration properly, using correctly rated parts, and ......... try not to touch one side of a power line while you stand in a puddle in your bare feet when you are working on it .... kidding :) !!

Despite all the hoopla about radio safety ... nobody who promotes the hoopla has ever documented one single case of a person being killed while working on or using old radios. Just use your brain.

Restore the radio according to the schematic and enjoy it.

cheers

EDIT :: don't go changing a whole pile of parts until you've checked to see if it works. Have a quick visual, change out the power supply filter caps and test run it. If there's any issues, fix those first, then do your restoration. If you are new to this, do one or two restoration parts at a time and then test it. That way you catch your mistakes quickly. You don't have to change all the resistors ... some people (very few) do ... it's a choice.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Thu 13, 2019 2:03 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
In this instance the cabinet is metal and I forget how the cabinet is isolated from the AC line, but that is the only thing that is isolating it and if it unknowingly fails, radio operation won't be affected, but one may get a nasty shock.

The isolation transformer is just something I do to make me feel more safe.

Plus given that one puts out 126Vdc it can be an easy way to boost the audio output of an AA5 some given the B+ is then higher provided a resistor is used to drop 6Vac in the heater string and a resistor is used to drop the screen grid voltage to stock which puts the other tube voltages to stock value.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Thu 13, 2019 2:43 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7848
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Tube Radio wrote:
In this instance the cabinet is metal and I forget how the cabinet is isolated from the AC line, but that is the only thing that is isolating it and if it unknowingly fails, radio operation won't be affected, but one may get a nasty shock.


If, might, may, could .... not likely, especially if the repair work is done correctly.

Stay at home .... the odds are much better that you'll become a hood ornament for a texting driver than being killed by your radio.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Thu 13, 2019 11:29 pm 
Member
User avatar

Joined: Oct Sun 18, 2009 5:38 am
Posts: 3634
Location: Tyler, Texas 75707-4212
[rant]All of the safety talk we read on this Forum makes it seem that the original engineers were idiots, or at least reckless, unnecessary risk takers with little or no regard for the end user, be they adults, little children or even babies who "might" get killed or at least shocked by any old radio playing around the house. If I were them, I would be insulted, highly offended and probably more than a little angry that now, in the nanny world we live in, their professionalism and competency was questioned and even outright condemned by a bunch of largely self taught, judgmental radio "experts", despite the fact that the UL was established to ensure product safety in 1894. [/rant]

_________________
I'm right 97% of the time. Who cares about the other 4%!

-.-. --- .-.. -.. / ---.. ----- --...


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Fri 14, 2019 2:35 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
I don't think that anyone advising using an isolation transformer is saying the engineers didn't know what they were doing.

It's just that using one provides another level of safety.

Most AC/DC radios as wired switch the neutral meaning the chassis is live through the tube heaters when the switch is turned off.

One can rewire so the switch is in the hot wire, but in some instances that can introduce hum in the audio.

To each their own though.

If using an isolation transformer makes the OP feel safer then he should use one.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 8:39 am 
Member

Joined: Aug Sat 19, 2017 6:55 am
Posts: 52
Location: Glendale, AZ, USA
I think I touched a nerve. Sorry.
Kind of like on the Vintage Mustang Forum I'm on, some like to add modern things like better brakes, overdrive transmissions, etc, and some prefer to drive them as they came off the showroom floor over 50 years ago.

I will be adding an isolation transformer, but might not be in the radio itself. I've seen on you tube someone who built a dbt with isolation, and he has a switch to make it isolation only. Something to look into at least. I'm not doing it tomorrow, but somewhere down the road. I just have to remember for now not to play with it when it isn't in the cover.

I'm not saying the engineers of yesterday were bad, but things change, knowledge changes, etc.

Thanks again for the information, both for and against. It's all good to know.

Russ


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 8:56 am 
Member

Joined: Aug Sat 19, 2017 6:55 am
Posts: 52
Location: Glendale, AZ, USA
Another question.
More of a how does the forum work type question.

Is it ok to post pictures of our radios, and which forum would be the correct one if so?

On the car forums I am on, there are Project forums for posting progress on cars we are working on.
Granted, a radio shouldn't take months to restore/repair, but can I just post pictures in this forum seeing as mine is a communication receiver? I'm trying to catch up on reading here, but I have a long way to go.

I opened it up just now, and this thing is surprisingly clean. I was expecting a lot worse, or even a brick instead of a chassis. Now it is really hard to wait to power it up, but I don't want to risk blowing something up.

Thanks,
Russ


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 10:16 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
Sure the radio is fine without an isolation transformer just like a car with drum brakes will still stop.

But an isolation transformer makes the radio safer just like disc brakes make the car safer.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 10:28 am 
Member

Joined: Aug Sat 19, 2017 6:55 am
Posts: 52
Location: Glendale, AZ, USA
I definitely agree. It's worth it to ME, might not be to others.
Thanks,
Russ


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 10:36 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
You're welcome.

I too prefer an isolation transformer with any AC/DC radio that has a metal cabinet as the only thing between the cabinet and one side of the line is either chassis mounting grommets or when the ground buss is separate from the chassis and a single capacitor is used.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 2:25 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7848
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
russosborne wrote:
I definitely agree. It's worth it to ME, might not be to others.
Thanks,
Russ
.

This (above) is what counts. As long as the person doing the mods does them because they understand why they are doing them and it's for their reasons ... not because of some brainwashing by others in the paranoid crowd ... go for it. Having an external iso-trans is easy and there's no reversing to do later if you wish. Having done that, and no, I haven't researched it myself .... maybe examine how having the radio isolated affects RF grounding? ... now that the neutral connection has been lifted.

cheers


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 3:08 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
Having the neutral lifted affects RF grounding for sure.

That's why a safety rated capacitor should be used between the chassis and ground of the power cord going to the isolation transformer or neutral.

Or in instances where there's a ground rod just for radios the radio can be connected to that provided said radio has a terminal for ground that has a capacitor between it and the chassis or in instances where the chassis is isolated from the circuit by a capacitor the chassis can go straight to ground.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 3:14 pm 
Member
User avatar

Joined: Jul Mon 26, 2010 8:30 pm
Posts: 26024
Location: Annapolis, MD
Wow!!!---We always go beyond the question, but this has gotten pretty busy.....:)

Starting at age 13, I routinely repaired all manner of things--including AC/DC apparati--with no isolation transformer, DBT, Variac,---or even a GFCI. I'm still here because I somehow learned safe procedures---things that apply regardless of what you are working on.

There is a well-worn truism: If you try to "idiot-proof" something, there will be an idiot that can defeat your efforts.

I now use an isolation transformer on transformerless equipment because it is more convenient. If I abandon 65 years of experience, I can still get zapped...but, with the isolation transformer, making certain kind of test setups is easier.

There are all manner of things that can enhance safety. An overlapping set is the things that might give a false impression of safety. There is only one iron-clad rule: If you don't know what you are doing, no amount of equipment or tools is going to help you.

_________________
-Mark
"Measure voltage, but THINK current." --anon.


Top
 Profile  
 
 Post subject: Re: hallicrafters SW-500 schematic? And a safety?
PostPosted: Jun Sun 16, 2019 3:21 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20056
Location: Warner Robins, GA
I messed with a few transformerless radios and audio devices in my teens not even thinking about one side of the circuit being connected to one side of the line.

I'm quite lucky I didn't get killed.

I at one point took one device and added an aux input used with a transistor radio. I tried to feed an audio signal to said device as it could also record and the transformerless amp explains why one audio channel of my 8 track no longer worked after that.


Top
 Profile  
 
Post New Topic Post Reply  [ 22 posts ]  Moderator: Sandy Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: Exabot [Bot], rhrailfan and 8 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB