The power supply in my radio has audible hum in the background
and bypassing the diode rectifiers with capacitors does not eliminate the
hum. There is no hum when using battery power. The solution is to
build my own power supply. Does anyone have a design for a compact 6V
supply that I could build for this purpose?

Behold, author signalled from keyed 4-1000A filament:

The power supply in my radio has audible hum in the background and
bypassing the diode rectifiers with capacitors does not eliminate the
hum. There is no hum when using battery power. The solution is to build
my own power supply. Does anyone have a design for a compact 6V supply
that I could build for this purpose?

Indeedy I do!

http://geek.scorpiorising.ca/schematics/6vFilPower.png

Origionally designed for tube filaments, but will suit your purpose just
fine :-)

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

What is the DC current requirement of your radio (i.e. 500mA)? A very simple
supply can be made up of a common 9V walwart with some additional
components. Just open the walwart and add a 7805 regulator, a couple of
diodes (do increase the 7805's voltage to 6V), and a couple of caps.
Actually, it is possible to improve on the radio's built-in supply by adding
this circuit to it.

Let me know if you'd like instructions.

Noel
"author" wrote in message
news:01c3d31c$aa2c97a0$53c44a43@gwg1...
The power supply in my radio has audible hum in the background
and bypassing the diode rectifiers with capacitors does not eliminate the
hum. There is no hum when using battery power. The solution is to
build my own power supply. Does anyone have a design for a compact 6V
supply that I could build for this purpose?

"author" wrote in message news:01c3d31c$aa2c97a0$53c44a43@gwg1...
The power supply in my radio has audible hum in the background
and bypassing the diode rectifiers with capacitors does not eliminate the
hum. There is no hum when using battery power. The solution is to
build my own power supply. Does anyone have a design for a compact 6V
supply that I could build for this purpose?

First, don;t bother repsonding to the r2000swler@hotmail account, I
have
abandoned it because of all the porno spam I was receiving.

I am assuming you are talking about a modern, low power receiver, and
not some sort of ancient tube boat anchor. While high current, low
ripple
supplies can be built, they are very complex and expensive.
I would suggest a metal case, aluminium is easy to work.
For a 6V output I would start with 120V to 12V transformer. Radio
Shack
transformers will work, but if you could find a 30+ year old one made
by
Stancor or Triad, it will run much cooler (more iron in the core).
Buy or build a full wave brigge rectifier, and bypass each diode
with a 0.01uF cap. Use as large a filter cap, at least 1000uF(@20V),
but
as large as 20,000uF(@20V) will not hurt. Also use a
10uF(@20V)tantalum in parallel with the main capacitor. Then use a
7806 (or a LM317 or LM338 for higher current with the correct
programing resistors to set the output at 6.0V)
Add a 100uF(@10V or 12V) across the output of the 7806. I have found
the LM317, with the voltage set point bypassed by a 10uF(@12V) to be a
little quiter
then a 7806. Either will be much quiter then almost any "store bought"
power supply. If you want to get fancy, put a corecom RFI filter on
the AC
mains input and do not use a neon pilot light, they often add a lot of
hash.
I have had good luck not connecting the ground of the DC out to the
power mains ground, it seams to always add a lot of noise. I prefer to
only ground my radio to a "real" ground.
You may have to mount the 7806 regulator on a heatsink, but for most
modern
SWs the metal case will work fine. Oh and be sure to add a 1amp fast
blow fuse on the input. You could also just get a 12V DC wallwart and
build a 7806 add on
regulator. The main issue with that approach will be the difficulty of
gaining
access to bypass the internal diodes. A better approach would be to
find a 12V AC (lots of modems use these) wall wart and then you will
use a bridge internal to your regulator.
Go to your local library and look for the ARRL handbook, or for any
"electronic
project" book, they all should have similar diagrams.
Good listening.

Nice schematic diagram, Gregg, but quite a complex circuit for use on a solid
state receiver

I have a simple one I built for my DX-392, using an LM317T, a pot for setting
the desired voltage, and the usual parts, including a center tapped 6.3 vac
transformer. I bought all of the parts, including the minibox, at Radio Shack.

I guess I'd better get busy and post my drawing as a web page. I first wanted
to refine it with notes so others could build it.

Bill, K5BY

(WShoots1) with the help of 999 monkeys eventually
managed to type:

Nice schematic diagram, Gregg, but quite a complex circuit for use on a solid
state receiver

I have a simple one I built for my DX-392, using an LM317T, a pot for setting
the desired voltage, and the usual parts, including a center tapped 6.3 vac
transformer. I bought all of the parts, including the minibox, at Radio Shack.

I guess I'd better get busy and post my drawing as a web page. I first wanted
to refine it with notes so others could build it.

Do you heatsink the LM317T? I've been using a similar circuit
(substituting a wall wart for the transformer) as a battery charger
and the heatsink barely gets warm. I wonder if it'd be possible to
build a really compact unit without the heatsink, maybe even putting
it inside the wallwart package.


--
A lie gets halfway around the world before the truth has a chance to
get its pants on, but what was the truth doing with no pants on in the
first place? --Winston Churchill

On Tue, 6 Jan 2004 19:44:01 -0600, Charles Hawtrey wrote


I'm in the middle of slightly rebuilding a couple of old radios and I need a
very few parts (our only electronics store is gone because of the health of
the owner [sigh].


What are y'all's recommendations for a component mail order house?

I'm specifically looking for one where there won't be a $15 shipping charge
on five dollars worth of parts.

As always/Thank you very much.



Gray Shockley
--------------------------
Entropy Maintenance Technician
Tao Chemical Company
--------------------------

http://www.compcomm.com/
Vicksburg, Mississippi US




wonderful .sig line!

--
A lie gets halfway around the world before the truth has a chance to
get its pants on, but what was the truth doing with no pants on in the
first place? --Winston Churchill

"Gray Shockley" wrote in message
.com...
On Tue, 6 Jan 2004 19:44:01 -0600, Charles Hawtrey wrote

I'm in the middle of slightly rebuilding a couple of old radios and I
need a very few parts (our only electronics store is gone

It's been several years but I have ordered from Digikey in the past, have
you looked at them??? If you find a good place for small oders let me know
(or post it) as I have several small projects I need to wrap up this winter.
I've ordered too many circuit boards from Far. Rob Mills ~

"Gray Shockley" wrote in message
.com...
On Tue, 6 Jan 2004 19:44:01 -0600, Charles Hawtrey wrote


I'm in the middle of slightly rebuilding a couple of old radios and I
need a
very few parts (our only electronics store is gone because of the
health of
the owner [sigh].


What are y'all's recommendations for a component mail order house?

I'm specifically looking for one where there won't be a $15 shipping
charge
on five dollars worth of parts.

As always/Thank you very much.



Gray Shockley

Here's a few places I've done business with:

http://www.danssmallpartsandkits.net/

Dan has great prices and usually has a good turnaround time. I've been
100% satisfied. However, it's a one man operation, and there have been
times when he's been so backlogged that there have been newsgroup
threads wondering if Dan is still in business or even still alive.

http://www.oselectronics.com/

Ocean State Electronics offers a huge stock of odd hobbyist/repair
items. Unfortunately, sometimes they are out of stock of the things
they offer. I also had one of my orders delayed for no known reason.
But, overall, they're not bad. They offer the stuff I wish Radio Shack
would have carried.

http://www.digikey.com/

Excellent service. Their web order page shows how many of a particular
item they have in stock. Very quick turnaround. $5 fee if the order is
under $25, if I recall.

http://www.partsexpress.com/

Great for speakers. Some of their other parts such as electrolytics are
a pretty good deal. More excellent service.

Frank Dresser

Do you heatsink the LM317T?

Yes, just out of practice. Too, everthing is mounted on and in an aluminum box.

I think there'd be too much too put inside a wall wart.

As for small amounts of small parts that were inquired about by another...

I've had great succes in ordering non-Shack stuff from All Electronics:

http://www.allelectronics.com

I have a mail order catalog of theirs, too. In it is listed a multi-volt/1-amp
wall wart, but it is a switching power supply, which would probably cause noise
on the bands.

73,
Bill, K5BY