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 Power supply/ Battery Eliminator ripple Solution

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FrankB
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Join date : 2010-11-22

PostSubject: Re: Power supply/ Battery Eliminator ripple Solution   July 18th 2018, 6:35 pm

" Many so-called battery eliminators are unsuited to transistor power supply usage. "
 Too true!!!

I would like to add to Cliff's info:
This project will NOT provide enough current to run a car radio. The 1N4000 series is only good for 1A max current. Not to mention the tube tester transformer is not designed for continual high current loads.
 It will work great for most tabletop and pocket radios though.

 No sense letting the "factory smoke" out trying to over tax this unit current wise. 

REMEMBER: "A FUSE IS ELECTRICITY'S SAFETY VALVE". Use a fuse- or 2 for safety. 

Over the years I have run into a couple of cases where no matter how "pure" the DC is, you still get ripple noise in the radio, unless it is run from a real battery. I am not really sure why either.
 (It is a ...possibility... that the battery filtering 'lytic is bad in the radio. I never conclusively found out.)

If need be, you can make a capacitor multiplying circuit, to increase the filter capacitance with just a few low cost parts. These multiplier circuits are found in almost every schematics compendium book.

With minimal modification Cliff's PS would run a 1-2 tube radio also, and the higher voltage taps would provide enough B+ for it to work.
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Cliff Jones
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PostSubject: Power supply/ Battery Eliminator ripple Solution   July 10th 2018, 11:51 am

In a book I have-Repairing Transistor Radios by S. LIBES  Riders (# 270)
Chapter 9
 ...The A.C. ripple content of a battery eliminator should therefore be checked with a calibrated oscilloscope... A good eliminator should have less than a 1-volt (peak-to-peak) a-c ripple.
Since transistor power supplies require low voltage output, high capacitance electrolytic capacitors added to the filter system reduce the a-c ripple appreciably. Many so-called battery eliminators are unsuited to transistor power supply usage.


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Here is an illustration of a PACO B-10 battery eliminator designed to power transistorized equipment.   (ANALOG TYPE POWER SUPPLY)

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OF course you can use a switching power supply, with the caveat of RF noise being broad-band and difficult to suppress. And most switching power supplies are not multilevel voltage select-able.
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They also mention that you can construct your own.
Here are the parts needed.
1.  Silicon rectifier  maybe a 1N4000 series ( I would modify that to be a bridge type - less problems with filtering.
2.   Filament transformer (secondary taps of 1.5,3,5,6.3,7.5,12,20, 25, 30, 35,50 volts each) Similar to Stancore P-1834-3 or a scavenged tube tester power transformer.

3.  Switch for the primary (4 pole switch) switching from OFF-1 125V-2, 115V-3, 105V-4

4.  12 position Rotary switch ( to connect to each of the secondary filament winding's)
     the center switch conductor path connects to the diode ,
5.  a capacitor of 100ufd ,
6.  a resistor of 3.3kohms,
7.  and a 1000ufd 50v capacitor.
8.  two output connectors (your choice of style) banana sockets, binding posts, or alligator clips .

the resistor is connected to both capacitors positive leads between them.
the capacitors are connected to the common transformer ground on the secondary.
two output connectors , one goes to the 1000mfd electrolytic + and the other to common secondary transformer ground.

I thought this might be a fun construction project for those on a limited budget.

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