the 6.3 VAC is ok ,no need to go into the fuss for dc.
dont take my word for it, after making the nice rig put some diodes on the
ac line and you will not see anythig special..
73's




--
http://www.qsl.net/sv1hao


"Biz WDØHCO" wrote in message
...
After 31 years and a bunch of parts in the garage, I am finally building
my
dream CW receiver from scratch.

Just wondering if I converted the 6.3 VAC filament voltage to a DC voltage
if doing so would be worth the effort to reduce hum.

Opinions ?

Also I would like to cut a round 4" diameter hole in the 1/8" aluminum
front
panel for the speaker grill. Is there a way to do this without a Greenlee
Pneumatic punch? I have a jig saw which I can cut square holes but round
holes are another matter. Is there a better way? I can drill round holes
up
to 7/8" with a unibit but I think 7/8" is as big as they get.

Thanks

Biz - WDØHCO

the 6.3 VAC is ok ,no need to go into the fuss for dc.
dont take my word for it, after making the nice rig put some diodes on the
ac line and you will not see anythig special..
73's




--
http://www.qsl.net/sv1hao


"Biz WDØHCO" wrote in message
...
After 31 years and a bunch of parts in the garage, I am finally building
my
dream CW receiver from scratch.

Just wondering if I converted the 6.3 VAC filament voltage to a DC voltage
if doing so would be worth the effort to reduce hum.

Opinions ?

Also I would like to cut a round 4" diameter hole in the 1/8" aluminum
front
panel for the speaker grill. Is there a way to do this without a Greenlee
Pneumatic punch? I have a jig saw which I can cut square holes but round
holes are another matter. Is there a better way? I can drill round holes
up
to 7/8" with a unibit but I think 7/8" is as big as they get.

Thanks

Biz - WDØHCO

On Wed, 29 Oct 2003 19:54:51 GMT, Allen Windhorn
wrote:


If I did this I would put a 0.01 uF capacitor to ground at each
filament pin, to keep RF from propegating through the wires. I would
also put a resistor to ground somewhere in the string to bleed off any
stray leakage current (maybe 1000 ohms or so), otherwise you might get
voltage buildup that could cause problems.

In many audio amplifiers, the filament was powered from a 6.3 V
winding with a grounded centre tap. If the centre tap was not
available, a potentiometer was connected across the filament winding
and the wiper was connected to ground and the wiper was adjusted for
minimum hum.

In RF applications, using bypass capacitors to ground at each tube is
a good idea.

Paul OH3LWR

On Wed, 29 Oct 2003 19:54:51 GMT, Allen Windhorn
wrote:


If I did this I would put a 0.01 uF capacitor to ground at each
filament pin, to keep RF from propegating through the wires. I would
also put a resistor to ground somewhere in the string to bleed off any
stray leakage current (maybe 1000 ohms or so), otherwise you might get
voltage buildup that could cause problems.

In many audio amplifiers, the filament was powered from a 6.3 V
winding with a grounded centre tap. If the centre tap was not
available, a potentiometer was connected across the filament winding
and the wiper was connected to ground and the wiper was adjusted for
minimum hum.

In RF applications, using bypass capacitors to ground at each tube is
a good idea.

Paul OH3LWR

Bill Janssen wrote:
Swells8044 wrote:

Go to Home Depot get a 4 in.hole saw.They are made for wood but will
cut a few
holes in al.
Steve


And use oil or something to keep the Al. from sticking to the teeth.

Bill K7NOM


And DON'T try to use a hand drill! MUST use a drill press!

Bill Janssen wrote:
Swells8044 wrote:

Go to Home Depot get a 4 in.hole saw.They are made for wood but will
cut a few
holes in al.
Steve


And use oil or something to keep the Al. from sticking to the teeth.

Bill K7NOM


And DON'T try to use a hand drill! MUST use a drill press!

W7TI wrote:
On Wed, 29 Oct 2003 08:33:36 -0500, Eskay wrote:


There are also drill held hole cutters that have a lathe type cutter on
the end of a rotating arm..Mean looking device when it rotates but it
does a good job..


__________________________________________________ _______

I have one of these but I would NOT recommend it. Way too hard to
control and dangerous to boot. Use a hole saw instead.


I have used one of these to cut a hole in an aluminum panel. The panel
was clamped to a piece of pine and the table on my drill press. The drill
press was set to the lowest possible speed and the chuck was lowered slowly.
Took a while to cut and the cutter did get stuck a few times requiring
me to raise
the chuck and clear the problem. Did cut a nice hole, but required a
chissel
to break out the center and a file to clean up afterwards.

W7TI wrote:
On Wed, 29 Oct 2003 08:33:36 -0500, Eskay wrote:


There are also drill held hole cutters that have a lathe type cutter on
the end of a rotating arm..Mean looking device when it rotates but it
does a good job..


__________________________________________________ _______

I have one of these but I would NOT recommend it. Way too hard to
control and dangerous to boot. Use a hole saw instead.


I have used one of these to cut a hole in an aluminum panel. The panel
was clamped to a piece of pine and the table on my drill press. The drill
press was set to the lowest possible speed and the chuck was lowered slowly.
Took a while to cut and the cutter did get stuck a few times requiring
me to raise
the chuck and clear the problem. Did cut a nice hole, but required a
chissel
to break out the center and a file to clean up afterwards.

Paul Keinanen wrote:
On Wed, 29 Oct 2003 23:28:28 +0200, "Deos"
wrote:


the 6.3 VAC is ok ,no need to go into the fuss for dc.
dont take my word for it, after making the nice rig put some diodes on the
ac line and you will not see anythig special..


Using a single floating 6.3V secondary winding with a potentiometer
connected across it and the wiper connected to the ground and adjusted
for minimum hum should be enough.

This kind of system works quite well when you have a single high
sensitivity input (such as in a radio receiver), but if you have
multiple sensitive inputs (as in audio mixing consoles) you would need
a separate filament winding for each input tube, in order to be able
to adjust the filament balance without compromises. In such situations
a DC filament system would be simpler to implement.

Paul OH3LWR


Except for high gain AF stages, a center tapped filament winding with the
center tap grounded should be ok. Otherwise a resistor of a few hundred to
a few thousand ohms from each side to ground (resistors of identical value).
Use of a pot is probably overkill, but if you have one in the junk box and
room to mount it ok.

Paul Keinanen wrote:
On Wed, 29 Oct 2003 23:28:28 +0200, "Deos"
wrote:


the 6.3 VAC is ok ,no need to go into the fuss for dc.
dont take my word for it, after making the nice rig put some diodes on the
ac line and you will not see anythig special..


Using a single floating 6.3V secondary winding with a potentiometer
connected across it and the wiper connected to the ground and adjusted
for minimum hum should be enough.

This kind of system works quite well when you have a single high
sensitivity input (such as in a radio receiver), but if you have
multiple sensitive inputs (as in audio mixing consoles) you would need
a separate filament winding for each input tube, in order to be able
to adjust the filament balance without compromises. In such situations
a DC filament system would be simpler to implement.

Paul OH3LWR


Except for high gain AF stages, a center tapped filament winding with the
center tap grounded should be ok. Otherwise a resistor of a few hundred to
a few thousand ohms from each side to ground (resistors of identical value).
Use of a pot is probably overkill, but if you have one in the junk box and
room to mount it ok.