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

Biz WDØHCO wrote:

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

A jig-saw should be able to cut a 4 inch dia hole.
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..
73 de VE3JUA

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

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 writes:

On Tue, 28 Oct 2003 18:38:39 -0600, Biz WDØHCO wrote:

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 ?

AC will work fine, but here's the key: Don't ground either side of
the 6.3 volt line. Many hum problems are caused by ground loops
where one side of the filament voltage is run through the chassis.
Manufacturers used to do this to save a few pennies by having only
one filament wire. In a mass production situation this can be made
to work, but for one-off design it's easier and better to just keep
the filament voltage isolated from the chassis or anything else.
Use a twisted pair and run it from socket to socket.

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.

What about an inadvertent short between the cathode and filament?

Allen

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

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

Biz WDØHCO wrote:

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

A jig-saw should be able to cut a 4 inch dia hole.
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..
73 de VE3JUA