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 Post subject: Silvertone battery radio + battery eliminator
PostPosted: Mar Sat 07, 2009 10:47 pm 
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Posts: 4248
Location: MS
Me and a friend went to a "pre-estate" sale by some people that someone that he knows knew (yeah, one of those deals) to see about buying an "old record player". It turns out that the record players were BPC and a late '60's cheap Symphonic console stereo. NOT INTERESTED!

While I was looking around, I saw this Silvertone battery radio on a shelf. I turned it around and saw a battery eliminator inside! This sale was actually a living estate. The homeowner's husband recently passed away after 63 years of marriage and the lady was moving into a retirement home. I asked about the radio and figured I'd get the usual "that's not for sale, the kids want it" reply. The lady said to make her an offer. I offered $15 and she asked if I would go $20, which I did.

The radio case has some veneer damage; but, it can be fixed by someone who knows what they are doing. I was more interested in the power supply than the radio as these power supplies are getting scarce and usually not very cheap on greedbay.

There is a model number inside the radio; but, I can't see it without removing the chassis. It's a basic 4 tube battery radio that runs on a 1.5V-90V pack.

Image

Image


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 Post subject:
PostPosted: Mar Sun 08, 2009 4:02 am 
Silent Key

Joined: Jan Tue 16, 2007 11:48 pm
Posts: 9664
Location: Hueytown, AL
I'd say you and the lady both did well! Eliminator probably worth what you paid if it doesn't take too much to restore.


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 Post subject:
PostPosted: Mar Sun 08, 2009 4:17 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34328
Location: Sandpoint, IDAHO 83864
Heck,even with this tightwad, I would go $20 on that set. They are not the prime interests of me, but they are seeming to be becomming that way. And with the battery eliminator included, that's even better yet.

I would start the restoration efforts with the eliminator to make sure you have something to power the set when you get around to restoring it.
Curt

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(Connoisseur of the cold 807) CW forever!


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 Post subject:
PostPosted: Mar Sun 08, 2009 5:01 am 
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Joined: Dec Sun 07, 2008 7:05 am
Posts: 4248
Location: MS
Up until recently, these types of battery sets were usually not given a second look by collectors mainly due to the difficulty in powering them up.

Since AC sets are becomming more scarce and expensive, these battery sets may be the next best option since most can still be had for a reasonable price.

I have several of these types of battery radios and I've already restored a few. Many work very well to have such simple circuitry.


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 Post subject:
PostPosted: Mar Mon 09, 2009 3:15 am 
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Joined: Dec Sun 07, 2008 7:05 am
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Location: MS
Looks like the radio is a model 2441, which I can't find in any of my books or on nostalgiaair.org. The battery eliminator is an Electro Products model P. I opened it and they were nice enough to paste a schematic inside the case. The date on the schematic is March, 1946. It has a power transformer and a 5Y3 rectifier for the B+ and some type of solid state bridge rectifier for the filament supply.


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 Post subject:
PostPosted: Mar Mon 09, 2009 4:10 am 
Silent Key

Joined: Jan Tue 16, 2007 11:48 pm
Posts: 9664
Location: Hueytown, AL
Probably copper oxide rectifier. Some stay good, some bad. Also has some hi capacity low voltage filters for the filament supply, like 1500 mfd. Probably need replacing.


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 Post subject:
PostPosted: Mar Fri 13, 2009 4:23 am 
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Joined: Jan Fri 23, 2009 1:10 am
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radiotvnut wrote:
Looks like the radio is a model 2441, which I can't find in any of my books or on nostalgiaair.org. ....

It's on page 210 of Mark Stein's "Sears Silvertone Catalogs"
It is a model 2941 and was from 1941. It cost $13.95.


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 Post subject:
PostPosted: Mar Fri 13, 2009 5:15 am 
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Location: MS
jimsp wrote:
radiotvnut wrote:
Looks like the radio is a model 2441, which I can't find in any of my books or on nostalgiaair.org. ....

It's on page 210 of Mark Stein's "Sears Silvertone Catalogs"
It is a model 2941 and was from 1941. It cost $13.95.


Thanks for the information. That $13.95 price tag would equal a heck of a lot more in today's dollars.


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 Post subject:
PostPosted: Mar Fri 13, 2009 7:58 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 9739
Location: Omak,wa,usa
Hello radiotvnut
I just received a Silvertone farm radio to part of my early Bday gift
it's a model 2511 like 1940
Sincerely Rich


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 Post subject:
PostPosted: Jul Sat 10, 2010 2:48 am 
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Joined: Dec Sun 07, 2008 7:05 am
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Location: MS
I thought I'd give an update on the battery eliminator. This radio has long been fixed (just needed the usual bad caps, some resistors, and some rotten wiring replaced) and it works well. However, I just got around to repairing this particular battery eliminator.

The circuit design is such that it uses a power transformer with one 5V winding for the B+ rectifier (5Y3) and a 3.5V winding for the filament supply. The plates of the 5Y3 are tied together, making it a half wave rectifier; and, the tube gets it's plate voltage directly from the AC line. In this case, the B+ ground is "hot". Every cap was, of course, bad (a .05 uf "across the line" cap, a 20-10uf@160V electrolytic can, and a dual 1000uf,6.3V cardboard tubular cap). Also, the B+ filter resistor had risen from 2.5 Kohms to nearly 4Kohms and the bridge rectifier for the filament supply was dead. I replaced the 2.5Kohm resistor with a 2.2Kohm, 2W and I made a bridge rectifier from standard 1N4007 silicon diodes.

There is a tapped wirewound resistor in the filament line, which is connected to the three screw terminals on the front. The screw terminals are for a jumper which can be connected to bypass part, or all, of the resistor in order to obtain proper filament voltage for various tube counts. I had to bypass the resistor completely in order to achieve 1.5 VDC on an ordinary 4 tube RCA radio.

I did replace the power cord with a polarized type, with the neutral side going to ground. This power supply originally had an in-line power switch and I will place such a switch in the hot side of the line.

The only other thing that I might end up doing is replace the 5Y3 with a 1N4007 and a suitable dropping resistor. That should cut down on the amount of heat produced.

This now makes 3 battery eliminators. The other one being a similar Perma-Power unit and then there's one that I crudely built using a transformer from AES and an LM317 for the filament voltage regulator. The one I built is safer and more stable, since it uses a transformer both B+ and filament supplies and has voltage regulation.


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 Post subject:
PostPosted: Jul Sat 10, 2010 5:20 am 
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Location: Aurora Colorado
Glad to see you got it going. Those battery sets are really good players. :)

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 Post subject:
PostPosted: Jul Sun 11, 2010 1:28 am 
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Location: MS
There is one thing that's a little annoying with this Electro power supply. When connected to this Silvertone radio, there is a little 120 cycle hum and I can hear some slight oscillation when I tune off a station.

I have a Perma-Power eliminator and the problem is not there when I use that one.

On the electro unit, I've tried bridging electrolytic caps as well as clipping in a .01 uf cap across the various outputs and nothing helps. The only thing I have not done is remove the .047 uf "across the line" cap. Like I said earlier, the filament supply uses a transformer and is isolated. The B+ supply is rectified directly from the AC line.

On the perma-power unit, both filament and B+ supplies are derived from a power transformer and are isolated from the power line. There is also no AC line cap in this unit.


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 Post subject:
PostPosted: Jul Sun 11, 2010 1:41 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34328
Location: Sandpoint, IDAHO 83864
Try adding a .01uF, 1000 vdc capacitor across the diode that provides the B+ and see if that quiets it down.
Curt

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Curt, N7AH
(Connoisseur of the cold 807) CW forever!


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 Post subject:
PostPosted: Jul Mon 12, 2010 3:25 am 
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Joined: Mar Mon 16, 2009 12:57 am
Posts: 100
Location: ottawa ON
I have the same battery eliminator but the circuit diagram is unreadable. Did you find a diagram other than the one inside the metal case?


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 Post subject:
PostPosted: Jul Mon 12, 2010 4:19 am 
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Location: MS
No; but, I'll see if I can get a picture of the one inside the case and post it. It's still somewhat readable.


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 Post subject:
PostPosted: Jul Mon 12, 2010 4:37 am 
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Location: Livermore, CA
Sears called these battery eliminators "Power Shifters". Here are some of their schematics. A lot are similar.

http://www.nostalgiaair.org/PagesByMode ... 017907.pdf

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 Post subject:
PostPosted: Jul Mon 12, 2010 12:22 pm 
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Location: Warren, MI, USA 48093-6744 N42.50973 W83.02633
I have a model 2541

Image

My knobs were seriously rotted Tenite. I got some nice repro wood knobs from Mark Oppat, yes I know they don't match but I think they look better.

Mine has a Silvertone Power Shifter. The twisted battery cable looked like some local fauna had made a tasty snack, but it was near the end. I cut it off and had a tough time trying to resolder the plug. About the same time I was working on another radio that had a 6SA7 with a H-K short. The Power Shifter had an octal socket...so a little presto-chango and this is what I have now.

Image

It works well!

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 Post subject:
PostPosted: Jul Mon 12, 2010 8:07 pm 
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Joined: Apr Thu 12, 2007 3:24 am
Posts: 669
Location: Milwaukee,WI
My power shifter has a different schematic than the ones posted in the link a few posts above. I re-capped mine and used it for at least a year or so. One day I turned on the radio and had no sound. Brought the radio and supply to the bench and measured high B+ voltage at the filament wires. Wiring was in good shape and nothing touching together inside that should not have been. Further testing showed that windings inside the power transformer shorted and pumped about 60 volts to the filaments. Luckily I had a spare of the tube set and power shifter.

I too, love those Silvertone Farm radios. They are perfect for running in the summer when you don't need any more heat build up in your listening area.


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 Post subject:
PostPosted: Jul Wed 14, 2010 4:26 pm 
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Joined: Mar Mon 16, 2009 12:57 am
Posts: 100
Location: ottawa ON
You mentioned that the AC line feeds the rectifier directly. Would you run this device through an isolation transformer, or is there another workaround?


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 Post subject:
PostPosted: Jul Wed 14, 2010 5:13 pm 
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Joined: Dec Sun 07, 2008 7:05 am
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Location: MS
For maximum safety, you'd need to run this with an isolation transformer. I don't think shock from a hot chassis was a big concern back then. I have a late '40's kiddie record player that has one side of the AC line connected to the chassis. Which means the volume control shaft stands a 50/50 chance of being hot, depending on the plug position in the AC outlet. I don't think this arrangement would fly today.

As far as getting around the problem, AES sells a small transformer that has an HV winding and a 6.3 volt winding. I could remove the old transformer and rectifier tube, install the new transformer and use a silicon diode in place of the tube. The 6.3 volt winding could be used for the filaments. Instead of resistors for dropping the voltage to 1.5, I could use an LM317 voltage regulator to give me a regulated 1.5 volt output.


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