30-0-30 Transformer, home brew or buy
 

its you / Steve:
Check the thrift stores or garage sales........ buy an old or "not so old"
stereo receiver...... and presto..... a transformer and other parts for
cheap.
If you shop around you can pay almost next to nothing and of course it
probably won't work, but you may be surprised and it just may work fine.....
if it does work fine you may not need to build an amplifier.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
-----------------------------------------


its you wrote in message
...
Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$) I realize that
purchasing one would of course be the ideal situation, but I don't
particularily feel like spending 35$ for just a transformer... Anyone
have any recommendations where to look to buy one of these? Is
homebrewing one of these transformers relatively complicated? All
thoughs, including negative, are appreciated. Thanks in advance,
Steve

30-0-30 Transformer, home brew or buy
 

Don't try to wind your own mains transformer, it's just not a good idea. Buy
or salvage a commercially available one, it'll be much safer and easier.

its you wrote in message
...
Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$) I realize that
purchasing one would of course be the ideal situation, but I don't
particularily feel like spending 35$ for just a transformer... Anyone
have any recommendations where to look to buy one of these? Is
homebrewing one of these transformers relatively complicated? All
thoughs, including negative, are appreciated. Thanks in advance,
Steve

30-0-30 Transformer, home brew or buy
 

It's probably cheaper to buy some scrap, there is usualy in each bigger city
some elctronics surplus store, try garage sales with odd equipment. Wires, core
and all that will probably cost more.

You can do it yourself, the biggest problem is inability to test the voltage
while you are making it, in order to test it you must almost complete it, then
you find that the voltages do not match with or without the load and then you
must take it apart again.

its, you wrote:

Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$) I realize that
purchasing one would of course be the ideal situation, but I don't
particularily feel like spending 35$ for just a transformer... Anyone
have any recommendations where to look to buy one of these? Is
homebrewing one of these transformers relatively complicated? All
thoughs, including negative, are appreciated. Thanks in advance,
Steve

30-0-30 Transformer, home brew or buy
 

Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$)

Steve-

You would need a large, tape-wound toroidal core to operate at the power
frequency. A ferrite core is not likely to be adequate for your needs.

If I were trying to make my own transformer, I'd look for a junker that had the
desired power rating (120 watts in your case), and replace the secondary. To
be sure there is enough room to wind the new secondary, perhaps a higher power
transformer would give some margin.

You can wind a test secondary, measure voltage, and calculate the required
number of turns to get the voltage you want. Give it a little extra to account
for IR drop.

To ensure an exact center tap, you might wind two pieces of wire at once
(bifilar winding) and connect them in series-aiding.

Good luck.

Fred

30-0-30 Transformer, home brew or buy
 

its you wrote in message
...
And, just out of curiousity, how would one go about winding a
torroidal transformer?

Assuming you could obtain a toroidal mains transformer core (those ferrite
rings are not the same thing at all) you would have a nightmare trying to
wind it. They are factory wound using a long thin spool holding the
enamelled wire which is fed through the hole in the middle of the toroid
over and over to get the right number of turns. You'd have to be a very
determined hobbyist to build a toroid winder in the home!

Unless, of course, someone knows another way of doing it...

Dave

30-0-30 Transformer, home brew or buy
 

There are a lot of design issues involved in winding a transformer - too
many to get into here in detail. Your basic issues a

1) Core material and saturation level
2) Enough primary windings to get sufficient field but not saturate core.
3) Thickness of primary winding.
4) Isolation between primary and secondary.
5) Secondary winding - turns and thickness.
6) Losses and temperature rise.
7) Change of characteristics as temperature rises.
8) Making it fit on a particular core/bobbin.

Best would be to find a transformer of similar power level where the primary
is wound first and you can remove the secondary and replace with your own.

I have a big Excel spreadsheet somewhere which assists in transformer design
but I'm not sure I can still find it and it does require some knowledge and
experience to use.


its you wrote in message
...
Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$) I realize that
purchasing one would of course be the ideal situation, but I don't
particularily feel like spending 35$ for just a transformer... Anyone
have any recommendations where to look to buy one of these? Is
homebrewing one of these transformers relatively complicated? All
thoughs, including negative, are appreciated. Thanks in advance,
Steve

30-0-30 Transformer, home brew or buy
 

I thought of stacking two commonly avaliable 30VCT transformers, but
didn't know if this was good practice. Any thoughts?
And, just out of curiousity, how would one go about winding a
torroidal transformer? would the primary and both secondaries all be
parallel windings, or would you wind one on one side and the other two
on the other? I probably won't do it myself, as I have a spare
amplifier with a transforemr that'll give me the voltages I need, but
the reason I'm building is to make a portable monitor, and space is
kind of tight...kind of really tight Thanks for the replies, Steve
On Sun, 20 Jul 2003 14:28:34 GMT, lcoe
wrote:

its wrote:
Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$) I realize that
purchasing one would of course be the ideal situation, but I don't
particularily feel like spending 35$ for just a transformer... Anyone
have any recommendations where to look to buy one of these? Is
homebrewing one of these transformers relatively complicated? All
thoughs, including negative, are appreciated. Thanks in advance,
Steve

how about stacking two bell xfmrs? the 18v model s/b close to what
you need and s/b cheap at Hdepot of Lowes. --Loren

30-0-30 Transformer, home brew or buy
 

how about stacking two bell xfmrs? the 18v model s/b close to what
you need and s/b cheap at Hdepot of Lowes. --Loren


You won't get enough current out of that for an amplifier, well unless it's
a rather small one.

Transformers can be stacked just fine though.

30-0-30 Transformer, home brew or buy
 

"Dave D" wrote to "All" (20 Jul 03 16:26:52)
--- on the topic of " 30-0-30 Transformer, home brew or buy"

DD From: "Dave D"

DD its you wrote in message
DD ...
And, just out of curiousity, how would one go about winding a
torroidal transformer?

DD Assuming you could obtain a toroidal mains transformer core (those
DD ferrite rings are not the same thing at all) you would have a nightmare
DD trying to wind it. They are factory wound using a long thin spool
DD holding the enamelled wire which is fed through the hole in the middle
DD of the toroid over and over to get the right number of turns. You'd
DD have to be a very determined hobbyist to build a toroid winder in the
DD home!
DD Unless, of course, someone knows another way of doing it...

Sure start with a transformer with a higher voltage rating than needed
and remove as many turns as required from the secondary. I've done this
a few times with big 1:1 transformers to bring them down to 50Vct. It's
solidly mounting the lead's that's the real bugger.

.... I know flyback, ultor, and 47 other dangerous words.

30-0-30 Transformer, home brew or buy
 

"Asimov" wrote in
message ...
"Dave D" wrote to "All" (20 Jul 03 16:26:52)
--- on the topic of " 30-0-30 Transformer, home brew or buy"

DD From: "Dave D"

DD its you wrote in message
DD ...
And, just out of curiousity, how would one go about winding a
torroidal transformer?

DD Assuming you could obtain a toroidal mains transformer core (those
DD ferrite rings are not the same thing at all) you would have a
nightmare
DD trying to wind it. They are factory wound using a long thin spool
DD holding the enamelled wire which is fed through the hole in the
middle
DD of the toroid over and over to get the right number of turns. You'd
DD have to be a very determined hobbyist to build a toroid winder in the
DD home!
DD Unless, of course, someone knows another way of doing it...

Sure start with a transformer with a higher voltage rating than needed
and remove as many turns as required from the secondary. I've done this
a few times with big 1:1 transformers to bring them down to 50Vct. It's
solidly mounting the lead's that's the real bugger.


I actually meant another way of winding a toroidal transformer...

Dave

30-0-30 Transformer, home brew or buy
 

James Sweet wrote:


how about stacking two bell xfmrs? the 18v model s/b close to what
you need and s/b cheap at Hdepot of Lowes. --Loren


You won't get enough current out of that for an amplifier, well unless it's
a rather small one.

Transformers can be stacked just fine though.

Bell transformers that I am failure with are designed to limit current
in case the secondary should become shorted. As such they have poor
voltage regulation with changing loads.

Bill K7NOM

30-0-30 Transformer, home brew or buy
 

its wrote:
As I expected, way more effort than I wanted to put into it. I can
get good quality 30VCT transformers very easily. According to James
Sweet it would be fine to stack these. Sounds like the solution I
need, these xformers are the right size and current I need, and
cheap...probably just do this. Thanks for all the good posts, Steve
On Sun, 20 Jul 2003 16:57:42 GMT, "Peter Gottlieb"
wrote:

the actual output of a bell xfmr is higher w/no or light load, and as
others point out, drops significantly w/increased/short loading. but
with only a 1a requirement, you may still consider this option.
they also make (commonly avail) 24vac models designed for a/c, where
control wiring is longer. these put out about 36vac unloaded.

good luck, --Loren

There are a lot of design issues involved in winding a transformer - too
many to get into here in detail. Your basic issues a

1) Core material and saturation level
2) Enough primary windings to get sufficient field but not saturate core.
3) Thickness of primary winding.
4) Isolation between primary and secondary.
5) Secondary winding - turns and thickness.
6) Losses and temperature rise.
7) Change of characteristics as temperature rises.
8) Making it fit on a particular core/bobbin.

Best would be to find a transformer of similar power level where the primary
is wound first and you can remove the secondary and replace with your own.

I have a big Excel spreadsheet somewhere which assists in transformer design
but I'm not sure I can still find it and it does require some knowledge and
experience to use.


its you wrote in message
. ..
Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$) I realize that
purchasing one would of course be the ideal situation, but I don't
particularily feel like spending 35$ for just a transformer... Anyone
have any recommendations where to look to buy one of these? Is
homebrewing one of these transformers relatively complicated? All
thoughs, including negative, are appreciated. Thanks in advance,
Steve

30-0-30 Transformer, home brew or buy
 

I wouldn't use bell transformers for this project, a local shop sells
good xformers designed for projects such as this at about 6$, just at
30VCT instead of 60. Kind of related, I've been using a bell
transformer for a power supply for quite some time now (simple LM317
circuit), provides a good 1.5A at around 22V continuiously. I'm sure
if I upped the current w/ a more hefty regulator circuit it would fail
quickly, but it's worked for a few years now w/ no sign of giving up
(I don't really care if it does, no big loss, but it's a nice under
table supply w/ the switched potentiometer sticking out, provides for
a quick 1.2-22VDC. Again, thanks for the posts, especially for
driving me away from the torroidal idea, i'm sure it would have ended
up in a headache and much wasted wire. Thanks, Steve
On Sun, 20 Jul 2003 23:41:03 GMT, lcoe
wrote:

its wrote:
As I expected, way more effort than I wanted to put into it. I can
get good quality 30VCT transformers very easily. According to James
Sweet it would be fine to stack these. Sounds like the solution I
need, these xformers are the right size and current I need, and
cheap...probably just do this. Thanks for all the good posts, Steve
On Sun, 20 Jul 2003 16:57:42 GMT, "Peter Gottlieb"
wrote:

the actual output of a bell xfmr is higher w/no or light load, and as
others point out, drops significantly w/increased/short loading. but
with only a 1a requirement, you may still consider this option.
they also make (commonly avail) 24vac models designed for a/c, where
control wiring is longer. these put out about 36vac unloaded.

good luck, --Loren

There are a lot of design issues involved in winding a transformer - too
many to get into here in detail. Your basic issues a

1) Core material and saturation level
2) Enough primary windings to get sufficient field but not saturate core.
3) Thickness of primary winding.
4) Isolation between primary and secondary.
5) Secondary winding - turns and thickness.
6) Losses and temperature rise.
7) Change of characteristics as temperature rises.
8) Making it fit on a particular core/bobbin.

Best would be to find a transformer of similar power level where the primary
is wound first and you can remove the secondary and replace with your own.

I have a big Excel spreadsheet somewhere which assists in transformer design
but I'm not sure I can still find it and it does require some knowledge and
experience to use.


its you wrote in message
...
Kind of an off question, but I'm searching for a 60V CT (30-0-30)
transformer (1-2A is fine) for an amplifier I've been building. Would
I be better off just shelling out the cash and getting one, or is it
realtively easy to build your own (there are all sorts of torridial
cores avaliable at a local store, all for under 5$) I realize that
purchasing one would of course be the ideal situation, but I don't
particularily feel like spending 35$ for just a transformer... Anyone
have any recommendations where to look to buy one of these? Is
homebrewing one of these transformers relatively complicated? All
thoughs, including negative, are appreciated. Thanks in advance,
Steve