Biz WD=?ISO-8859-1?B?2A==?=HCO 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.

Depends on the tubes you're using. Some tube designs have real problem with
noise coupling from the filament, some do not.

Sometimes it varies, too. The Russian 6SN7 and 6SL7 tubes have serious
coupling issues, the old Raytheons do not. But the old GEs do. If you
run DC, you don't have to worry about it.

Running DC filaments also means you can ramp the filament supply up more
slowly too, by using big filter caps for a long time constant. This tends
to make tubes last longer.

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.

You CAN drill large holes in aluminum with a hole saw intended for wood.
Not one of the adjustable ones, but one of the formed metal ones like Black
and Decker sells, where you have one center assembly that holds a centering
bit and then a formed metal blade for each size that screws into the center
assembly. Run very, very slow and keep the blade as wet as possible with
cutting oil or automatic transmission fluid. If you are careful you can get
a nice cut this way. It will wear the blade a lot more quickly than wood,
of course.

However, if you do this a lot, a Greenlee punch is the way to go. You don't
need a hydraulic one either, just one of the screw-in ones that you crank down
by hand. Even so, a 4" punch will run you over a hundred bucks, as opposed
to fifteen or twenty bucks for a cheap hole saw kit.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:

You CAN drill large holes in aluminum with a hole saw intended for wood.
Not one of the adjustable ones, but one of the formed metal ones like Black
and Decker sells, where you have one center assembly that holds a centering
bit and then a formed metal blade for each size that screws into the center
assembly. Run very, very slow and keep the blade as wet as possible with
cutting oil or automatic transmission fluid. If you are careful you can get
a nice cut this way. It will wear the blade a lot more quickly than wood,
of course.
--scott

You want to cool the cutting tool, not lubricate it. The ATF is not a
great idea. Cutting oil is intended to cool the tool, to extend its
life. When you lube a bit or saw it tries to slide over the metal,
rather than cut it.

--


Michael A. Terrell
Central Florida

Scott Dorsey wrote:

You CAN drill large holes in aluminum with a hole saw intended for wood.
Not one of the adjustable ones, but one of the formed metal ones like Black
and Decker sells, where you have one center assembly that holds a centering
bit and then a formed metal blade for each size that screws into the center
assembly. Run very, very slow and keep the blade as wet as possible with
cutting oil or automatic transmission fluid. If you are careful you can get
a nice cut this way. It will wear the blade a lot more quickly than wood,
of course.
--scott

You want to cool the cutting tool, not lubricate it. The ATF is not a
great idea. Cutting oil is intended to cool the tool, to extend its
life. When you lube a bit or saw it tries to slide over the metal,
rather than cut it.

--


Michael A. Terrell
Central Florida

Biz WD=?ISO-8859-1?B?2A==?=HCO 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.

Depends on the tubes you're using. Some tube designs have real problem with
noise coupling from the filament, some do not.

Sometimes it varies, too. The Russian 6SN7 and 6SL7 tubes have serious
coupling issues, the old Raytheons do not. But the old GEs do. If you
run DC, you don't have to worry about it.

Running DC filaments also means you can ramp the filament supply up more
slowly too, by using big filter caps for a long time constant. This tends
to make tubes last longer.

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.

You CAN drill large holes in aluminum with a hole saw intended for wood.
Not one of the adjustable ones, but one of the formed metal ones like Black
and Decker sells, where you have one center assembly that holds a centering
bit and then a formed metal blade for each size that screws into the center
assembly. Run very, very slow and keep the blade as wet as possible with
cutting oil or automatic transmission fluid. If you are careful you can get
a nice cut this way. It will wear the blade a lot more quickly than wood,
of course.

However, if you do this a lot, a Greenlee punch is the way to go. You don't
need a hydraulic one either, just one of the screw-in ones that you crank down
by hand. Even so, a 4" punch will run you over a hundred bucks, as opposed
to fifteen or twenty bucks for a cheap hole saw kit.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

That would cut down on hum or the potential for heater cathode leakage
induced hum. I have never heard hum on a battery operated radio.

Michael A. Terrell wrote:

Biz WDØHCO wrote:

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

That would cut down on hum or the potential for heater cathode leakage
induced hum. I have never heard hum on a battery operated radio.

Michael A. Terrell wrote:

Biz WDØHCO wrote:

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

I'll be damned if I wouldn't call around to some sheetmetal shops and
see if one of them has a punch press that would cut that out! I
wouldn't mess it up! Good luck...Blue On Tue, 28 Oct 2003 18:38:05
-0600, 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

On 4 Nov 2003 21:37:23 -0600, Blue Crown wrote:

I'll be damned if I wouldn't call around to some sheetmetal shops and
see if one of them has a punch press that would cut that out! I

Try some of the local electricians.
Turned out one of my neighbors had a set all the way up to 4 inches.
When I was running conduit for the coax in the shop last week end.

You can also do the same with a bi-metal hole saw, but that takes a
lot of clamping and a very sturdy drill press to get a neat hole. The
hole punches are by far the better choice.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)

wouldn't mess it up! Good luck...Blue On Tue, 28 Oct 2003 18:38:05
-0600, Biz WDØHCO wrote:

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

snip