On Sat, 25 Oct 2008, raypsi wrote:

Date: Sat, 25 Oct 2008 10:25:23 -0700 (PDT)
From: raypsi
Newsgroups: rec.radio.amateur.homebrew
Subject: I built a 7.5VAC 21Amp transformer now it has lots of buzz

Hey all:

I tore down a transformer I got from ebay it was a Zenith TV power
transformer from days gone by. Re wound it with 17AWG wire on the
secondary and primary. It powers up my 4-1000A filament nicely with
7.25VAC from 120VAC mains. I used a penta-filar winding on the
secondary. Shimmed the bobbin in the core window with some 1/8 thick
virgin teflon. Epoxied the windings to the bobbin. This was a 240VA
transformer and now is a 83watt buzzer / 157watt filament transformer.

So what is the cheapest I can gits away with sealing these laminations
from buzzing, I used up all my epoxy sealing the windings.

73

n8zu


This might be a little "far-out" but, besides just buying more epoxy and
just doing it right, maybe you could find a can or metal box, put the
transformer into the box, and fill the box up with enough sand that you
have 1-2 inches all around the transformer, and that might muffle the
buzz. You'll need to worry about heat dissipation through that sand which
will act like an insulator, but if you are on the air only a couple of
hours per day, it should not get dangerously hot (however, many of the old
hermetically sealed transformers were burried in a waxy-tar that was
quite hard at room temperature).

Your other option is to figure out some clamping arrangement so that the
laminations are held close and tight.

Re-winding transformers is fun, but next time you want some off-beat
voltage, maybe scrounge up higher voltages (eg. car battery chargers)
and use either a variac or power resistor (with sufficient heat
dissipation) to bring the voltage down to where you want it and save
yourself the headaches and earaches. Or, don't take the laminations apart
but feed the wire (stranded) through the holes that are left.

Or, other kludge-cheapskate approaches.

Good luck.

Howdy Hank,

Thanks for the follow-up! Perhaps they used a voltage regulating
transformer. I think some of the telcom rectifiers used them.
I know some mainframe computers did.

It's still a curiosity to me. Though I've seen enough occult
behavior from wound magnetic devices that I wouldn't discount it,
I'm tempted to wonder if there's another variable that was
coincident with the welded laminations.

73



"Henry Kolesnik" wrote in
:

Grumpy
Years ago in 93 or so on a Telco fiber system by Alcatel we took severe
hits when the air conditioner came on and it was traced to the station
rectifier. The Gould rectifiers had a weld bead and when we replaced
them another make which I can't recall that didn't have weld beads the
problem went away. Its quite strange since the rectifiers floated big
batteries but a vco in system was sensitive to the spike. After doing
some research I found an explanation that I can't recall because I was
too busy with other problems and mine had gone away. Alcatel spent
several hundred thousand trying to find the problem and I stumbled on to
it by shear luck.

73
Hank WD5JFR

It's not so far out of a suggestion. One of my Zenith console
radios has some remote control solenoid mounted inside a metal
box that's lined with rubber.

The sand is a pretty good thermal conductor (compared to air),
better than epoxy. In fact they fill the cheaper type of epoxy
potting material with coarse quartzite or powdered limestone
to improve its the thermal conductivity. It's the air trapped
between the grains of sand that provide some thermal insulation.
Mixing sand with epoxy or oil fills the interstaces which would
otherwise be filled with air.

Some one mentioned coating the laminations with nail polish as you
stack them up to glue them together. Either that or little varnish
would most likely have prevented any buzzing laminations.

Not taking the laminations off is a good suggestion too if it's
possible. For instance microwave oven transformers just chisel
off the secondary and wind a new one. Though for smaller
transformers that often isn't possible.




Stray Dog wrote in
.org:


This might be a little "far-out" but, besides just buying more epoxy
and just doing it right, maybe you could find a can or metal box, put
the transformer into the box, and fill the box up with enough sand
that you have 1-2 inches all around the transformer, and that might
muffle the buzz. You'll need to worry about heat dissipation through
that sand which will act like an insulator, but if you are on the air
only a couple of hours per day, it should not get dangerously hot
(however, many of the old hermetically sealed transformers were
burried in a waxy-tar that was quite hard at room temperature).

Your other option is to figure out some clamping arrangement so that
the laminations are held close and tight.

Re-winding transformers is fun, but next time you want some off-beat
voltage, maybe scrounge up higher voltages (eg. car battery chargers)
and use either a variac or power resistor (with sufficient heat
dissipation) to bring the voltage down to where you want it and save
yourself the headaches and earaches. Or, don't take the laminations
apart but feed the wire (stranded) through the holes that are left.

Or, other kludge-cheapskate approaches.

Good luck.

On Oct 27, 11:29*pm, Stray Dog wrote:
On Sat, 25 Oct 2008, raypsi wrote:
Date: Sat, 25 Oct 2008 10:25:23 -0700 (PDT)
From: raypsi
Newsgroups: rec.radio.amateur.homebrew
Subject: I built a 7.5VAC 21Amp transformer now it has lots of buzz

Hey all:

I tore down a transformer I got from ebay it was a Zenith TV power
transformer from days gone by. Re wound it with 17AWG wire on the
secondary and primary. It powers up my 4-1000A filament nicely with
7.25VAC from 120VAC mains. I used a penta-filar winding on the
secondary. Shimmed the bobbin in the *core window *with some 1/8 thick
virgin teflon. Epoxied the windings to the bobbin. This was a 240VA
transformer and now is a 83watt buzzer / 157watt filament transformer.

So what is the cheapest I can gits away with sealing these laminations
from buzzing, I used up all my epoxy sealing the windings.

73

n8zu

This might be a little "far-out" but, besides just buying more epoxy and
just doing it right, maybe you could find a can or metal box, put the
transformer into the box, and fill the box up with enough sand that you
have 1-2 inches all around the transformer, and that might muffle the
buzz. You'll need to worry about heat dissipation through that sand which
will act like an insulator, but if you are on the air only a couple of
hours per day, it should not get dangerously hot (however, many of the old
hermetically sealed transformers were burried in a waxy-tar that was
quite hard at room temperature).

Your other option is to figure out some clamping arrangement so that the
laminations are held close and tight.

Re-winding transformers is fun, but next time you want some off-beat
voltage, maybe scrounge up higher voltages (eg. car battery chargers)
and use either a variac or power resistor (with sufficient heat
dissipation) to bring the voltage down to where you want it and save
yourself the headaches and earaches. Or, don't take the laminations apart
but feed the wire (stranded) through the holes that are left.

Or, other kludge-cheapskate approaches.

Good luck.- Hide quoted text -

- Show quoted text -

I have always dunked them in varnish but only got some success with
this by
drawing a vaccum then applying pressure. I used an old compressor
from
a refrigarator to do this. The tank was made from from pipe and
fittings. The best
results I got was winding the core on a block of wood cut the same
size as
the core wrapping the wood with cardboard then windng the coil then
pushed
then put the core together. I was 18 at the time and a very talented
man
named Olin Griggs helped me with this project and let me use his
shop.
Olin was a retired engineer that had worked for GE at their
Bloomington plant.
Since then the onl transformers I have wound that havent bussed to
much
was by modifying a ready built transformer. USually this meant one
that I
on which I could keep the primary winding intact. Lately I have gotten
interested
in SMPSs for doing this sort of thing. It is very easy to see why
industry has
has made the move to them.

Jimmie

Hey Grump
A transformer is one of the simplest electrical machines and pretty well
understood in the classical design but when some of the parameters are
changed we don't have much experience or investigation and probably
wont. Hot swappable rectifier modules have made transformer based
rectifiers uneconomical kinda like carburetors and fuel injection. If
you have the time, check with some of the old time designers of
transformer rectifiers. Let me now what you find out. I had some notes
but those are long gone.
Hank
"Grumpy The Mule" wrote in message
...
Howdy Hank,

Thanks for the follow-up! Perhaps they used a voltage regulating
transformer. I think some of the telcom rectifiers used them.
I know some mainframe computers did.

It's still a curiosity to me. Though I've seen enough occult
behavior from wound magnetic devices that I wouldn't discount it,
I'm tempted to wonder if there's another variable that was
coincident with the welded laminations.

73



"Henry Kolesnik" wrote in
:

Grumpy
Years ago in 93 or so on a Telco fiber system by Alcatel we took
severe
hits when the air conditioner came on and it was traced to the
station
rectifier. The Gould rectifiers had a weld bead and when we replaced
them another make which I can't recall that didn't have weld beads
the
problem went away. Its quite strange since the rectifiers floated
big
batteries but a vco in system was sensitive to the spike. After
doing
some research I found an explanation that I can't recall because I
was
too busy with other problems and mine had gone away. Alcatel spent
several hundred thousand trying to find the problem and I stumbled on
to
it by shear luck.

73
Hank WD5JFR

I left out switch based hot swappable
"Henry Kolesnik" wrote in message
...
Hey Grump
A transformer is one of the simplest electrical machines and pretty
well understood in the classical design but when some of the
parameters are changed we don't have much experience or investigation
and probably wont. Hot swappable rectifier modules have made
transformer based rectifiers uneconomical kinda like carburetors and
fuel injection. If you have the time, check with some of the old time
designers of transformer rectifiers. Let me now what you find out. I
had some notes but those are long gone.
Hank
"Grumpy The Mule" wrote in message
...
Howdy Hank,

Thanks for the follow-up! Perhaps they used a voltage regulating
transformer. I think some of the telcom rectifiers used them.
I know some mainframe computers did.

It's still a curiosity to me. Though I've seen enough occult
behavior from wound magnetic devices that I wouldn't discount it,
I'm tempted to wonder if there's another variable that was
coincident with the welded laminations.

73



"Henry Kolesnik" wrote in
:

Grumpy
Years ago in 93 or so on a Telco fiber system by Alcatel we took
severe
hits when the air conditioner came on and it was traced to the
station
rectifier. The Gould rectifiers had a weld bead and when we
replaced
them another make which I can't recall that didn't have weld beads
the
problem went away. Its quite strange since the rectifiers floated
big
batteries but a vco in system was sensitive to the spike. After
doing
some research I found an explanation that I can't recall because I
was
too busy with other problems and mine had gone away. Alcatel spent
several hundred thousand trying to find the problem and I stumbled
on to
it by shear luck.

73
Hank WD5JFR

Howdy Hank,

I've been designing switch mode magnetics for about
thirty years now. The more I learn the less I know.
It's true that the principles are well known but the
implementation is a morass of compromises. At the
power level many of my designs operate at, second
and third order effects can suddenly become serious
and unexpected design complications. Some people
enjoy puzzles. I guess that's why I like designing
this sort of stuff.

I've worked on a lot of weird stuff, big cap charging
supplies, pulse compressors, very high voltage or high
current, and tiny stuff with extremely low noise outputs.
But I don't have much experience with line frequency
magnetics beyond EMI filters. As you say there's
not much call for it now. But unfettered by
all the weak components the big iron can support
amazing overloads, so I think there's still a place
for it. At least for now. The cost of steel and
copper (and the transportation costs) for such heavy
beasts is certainly making them increasingly less
attractive.

Lately I've been working on equipment in the 10KW-60KW
output range switching at 75KHz range. The whole system
weighs much less than just the line frequency transformer
that would be required alone.

The only big iron guys I know are now retired or dead.
And the companies I've dealt with that make that stuff
tend to have very little engineering staff, not much new
going on, (other than some efficiency improvements from
amorphous cores) they just crank out the product in cook
book fashion. I think nuances of it may soon be a lost.


73


"Henry Kolesnik" wrote in
:

Hey Grump
A transformer is one of the simplest electrical machines and pretty well
understood in the classical design but when some of the parameters are
changed we don't have much experience or investigation and probably
wont. Hot swappable rectifier modules have made transformer based
rectifiers uneconomical kinda like carburetors and fuel injection. If
you have the time, check with some of the old time designers of
transformer rectifiers. Let me now what you find out. I had some notes
but those are long gone.
Hank

hey all:

A good trick for the lams is clear nail polish as you reassemble them.
Just a quick wipe, as it'll spread as you squeeze in the last few
lams
under a "Quick-Grip" clamp.

I could go to the nail shop get a peddicure and coat my lams at the
same time. A great idea if only I could handle the fumes.


Varnish is the best thing. Warm the varnish and the
transformer first before you dunk it. That will reduce
the viscosity and improve penetration. A little thinner
in the pot may help too.

I lucky I can stand the effects of epoxy but no way varnish. For nail
polish or varnish I gots to gits me a up or down draft venilator
exhastt system.

If you have bolts thru the lams have you torqued them to the point of
twisting them off? If you haven't you might want to loosen then and
add
some more varnish to the lams while they're loose and then torque
them

Thanks I retorqued them and that reduced the noise by 6db. Now I have
a less effecient buzzer

Bolts through the laminations should have insulators
(usually fiber board washers) under the heads. Just
one end will do, there's no need for them under the
nuts. But shoulder washers are best so the bolts don't
short any laminations together deeper into the core.

Good idea I seen many a transformer that had fiber spacers over the
whole length of the bolt plus fiber washers..


put the
transformer into the box, and fill the box up with enough sand that
you
have 1-2 inches all around the transformer, and that might muffle the
buzz. You'll need to worry about heat dissipation through that sand
which
will act like an insulator, but if you are on the air only a couple
of
hours per day,

I likes this one, but I gots alot of kittie litter that comes from
some place in Arkansas, it is mostly quartz and some other trace
minerals.

The only big iron guys I know are now retired or dead.
And the companies I've dealt with that make that stuff
tend to have very little engineering staff, not much new
going on, (other than some efficiency improvements from
amorphous cores) they just crank out the product in cook
book fashion. I think nuances of it may soon be a lost.

Yes lams are going the way of the dinosuars. Maybe that's why they
cost so much looky the price of a good audio output transformer for a
tube audio amplifier and they go up to at least 20Khz.

Your other option is to figure out some clamping arrangement so that
the
laminations are held close and tight.

Yes I think I will put together a vise of sorts. Custom made to fit
the transformer.

73 and thanks for all the good information.

n8zu

The only big iron guys I know are now retired or dead.
And the companies I've dealt with that make that stuff
tend to have very little engineering staff, not much new
going on, (other than some efficiency improvements from
amorphous cores) they just crank out the product in cook
book fashion. I think nuances of it may soon be a lost.

Yes lams are going the way of the dinosuars. Maybe that's why they
cost so much looky the price of a good audio output transformer for a
tube audio amplifier and they go up to at least 20Khz.

Your other option is to figure out some clamping arrangement so that
the
laminations are held close and tight.

Yes I think I will put together a vise of sorts. Custom made to fit
the transformer.
==============
Followed this thread with great interest .
Reason : I have an Astron RS-50A , 13.8V -50 Amperes unit for 220V-AC
input which is buzzing heavily. Upon switch-on the group circuit breaker
in the house sometimes trips due to the high switch-on current surge .
This can be overcome by adding a soft start circuit which initially puts
a say 25 Ohms-50Watts resistor in series with the primary transformer
winding ,shorting this resistor after a second or so.

However I fear that the main reason for the buzzing is that the
transformer (of US origin) was designed for 60 Hz ,whereas here in the
UK (like in all European countries ) the supply frequency is 50 Hz.
Can someone on this NG please confirm/reject my suspicion.

Another possible reason could be that the cabinet sheet metal which is
very close to the transformer is vibrating (transducer effect) .


TIA for any constructive advice/opinion

Frank GM0CSZ / KN6WH

On Oct 29, 8:21*am, Highland Ham wrote:
The only big iron guys I know are now retired or dead.
And the companies I've dealt with that make that stuff
tend to have very little engineering staff, not much new
going on, (other than some efficiency improvements from
amorphous cores) they just crank out the product in cook
book fashion. I think nuances of it may soon be a lost.

Yes lams are going the way of the dinosuars. Maybe that's why they
cost so much looky the price of a good audio output transformer for a
tube audio amplifier and they go up to at least 20Khz.

Your other option is to figure out some clamping arrangement so that
the
laminations are held close and tight.

Yes I think I will put together a vise of sorts. Custom made to fit
the transformer.

==============
Followed this thread with great interest *.
Reason : I have an Astron RS-50A *, 13.8V -50 Amperes *unit *for 220V-AC
input which is buzzing heavily. Upon switch-on the group circuit breaker
in the house sometimes trips due to the high switch-on current surge .
This can be overcome by adding a soft start circuit which initially puts
a say 25 Ohms-50Watts resistor in series with the primary transformer
winding ,shorting this resistor after a second or so.

However I fear that the main reason for the buzzing is that the
transformer (of US origin) was designed for 60 Hz ,whereas here in the
UK (like in all European countries ) the supply frequency is 50 Hz.
Can someone on this NG please confirm/reject my suspicion.

Another possible reason could be that the cabinet sheet metal which is
very close to the transformer is vibrating (transducer effect) .

TIA for any constructive advice/opinion

Frank * * GM0CSZ / KN6WH- Hide quoted text -

- Show quoted text -

Frank I emailed XXXXXXX's address to you. He designed the Astron Power
supply.


Jimmie