Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

"Mark Fortune" wrote in message
...
Greetings to the collective.

For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50) and
deliver up to 5amps of current. if my estimates are right i'll need a
600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had
a look at some transformers in this range, and they're a little out of my
price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Not really worth the effort, IMHO. However, take a look at All Electronics,
Hosfelt Electronics, MCM Electronics. There are others also. They have over
run surplus trannys with really good prices. The other alternative is try to
find an old high power am fm receiver which is kaput and not worth fixing.
They have a transformer with the approximate outputs you seek. You're right,
if you have the time, building your own power supply is fun and saves lots
of loot.
regards,
Tom

On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

By the time you have bought the core, be it toroid or E I lams, bought the
bobbin (if you use E I) bought two lots of wire, insulating fabric tape etc etc
etc., you may as well go and buy the right thing.

We make our own up to 3kVA, and we have all the bobbins, wire, varnish, tapes
etc., but before you ask, we don't do one-offs. Most of ours are specials that
we have designed by an outside consultant. Above 3kVA we go outside for them as
it isn't worth keeping all the steel strip, special wire and bigger winders,
varnish dip etc etc.

We have a pair of winding machines plus a hand winder which we can wind up to
3mm copper wire or small rectangular tape.

You may have to look around for what you want, but I promise you it will save
you a lot of time and trouble.

Peter
--
Peter & Rita Forbes
Email:
Web: http://www.oldengine.org/members/diesel

On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune
wrote:

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well.

No, it won't :-)
Your math is right. But what do you expect if you decide to draw
1 Volt at 5 amps from that beast ?
Who / what is going to dissipate the 600 - 5 = 595 VA for you ?

Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.

Here's your advice: don't even think of starting at 600 VA if you
want to roll your first transformer :-)


--
Kind regards,
Gerard Bok

On Tue, 8 Aug 2006 15:01:26 -0400, "t.hoehler"
wrote:


"Mark Fortune" wrote in message
.. .
Greetings to the collective.

For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50) and
deliver up to 5amps of current. if my estimates are right i'll need a
600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had
a look at some transformers in this range, and they're a little out of my
price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Not really worth the effort, IMHO. However, take a look at All Electronics,
Hosfelt Electronics, MCM Electronics. There are others also. They have over
run surplus trannys with really good prices. The other alternative is try to
find an old high power am fm receiver which is kaput and not worth fixing.
They have a transformer with the approximate outputs you seek. You're right,
if you have the time, building your own power supply is fun and saves lots
of loot.
regards,
Tom



I had 3 toroids made by Tortran a couple years ago for a homemade
audio amp, they where very reasonable. I recommend you tell them to
give you a non-thermo protected primary.

Mark Fortune wrote in
:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

By a lot of cheap toroidals on eBay, 5A at some low voltage that doesn't
sell well. Outputs in series, inputs in parallel. Switch-select to get
coarse adjust, variable regulate over one output's voltage range to get any
voltage over a large range with little loss.

In message , dated Tue,
8 Aug 2006, t.hoehler writes

Not really worth the effort, IMHO. However, take a look at All
Electronics, Hosfelt Electronics, MCM Electronics.

A bit difficult for a person based in UK, perhaps. And 60-0-60 V at
around 9 A is a BIG receiver or amplifier. Around 300 W/channel.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

I would recommend reading up from every source. I have built torroids
using the winding which was orginally a variac. These were 110 volt
units. You automatically have a primary so all you need to do is wind
the secondaries on top. I have also done the other type of transformer,
schelacing.the iron plates. I would also recomend what others have, buy
surplus on the market. Combine transformers if you can't find them.

greg

On Tue, 8 Aug 2006 20:51:44 +0100, John Woodgate
wrote:

In message , dated Tue,
8 Aug 2006, t.hoehler writes

Not really worth the effort, IMHO. However, take a look at All
Electronics, Hosfelt Electronics, MCM Electronics.

A bit difficult for a person based in UK, perhaps. And 60-0-60 V at
around 9 A is a BIG receiver or amplifier. Around 300 W/channel.

Sounds about right.

Years ago I had a neighbor kid who needed tutoring in Algebra.

I couldn't get him really interested until I sweetened the pie by
offering to help him build a 400W guitar amplifier IF he got an "A" in
Algebra.

He did get the "A".

We built this beautiful thing (in 1975) that was so heavy that it took
two people to carry it, and I had to use fans on the heat-sinks ;-)

Put out 400W RMS into 4 x 16 ohm speakers in parallel.

For my effort his father, President of Anthony Pools, built me a
swimming pool at a bargain price.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim



I couldn't get him really interested until I sweetened the pie by
offering to help him build a 400W guitar amplifier IF he got an "A" in
Algebra.

He did get the "A".

We built this beautiful thing (in 1975) that was so heavy that it took
two people to carry it, and I had to use fans on the heat-sinks ;-)

Put out 400W RMS into 4 x 16 ohm speakers in parallel.

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need

Do you have lots of time and money and power transistors to blow?

It's not too hard to build a power supply to your specs. It's a lot
harder to build one that will have a MTTF of a week or more. Are you
sure you can design a power supply that can survive the accidental
short circuit, reverse polarity across a car battery, static
discharges, inductive kicks, thermal cycles, and all the things that
bench power supplies have to tolerate?

In my experience, bench power supplies blow out about once a year.
Blown pass transistors, driver transistors, yuck.

You might consider just souping-up a PC power supply. Put a LM350 and
a foldback current limiter, switchable to the +5 and +12v outputs. Add
a hefty diode and low ESR capacitor to voltage-double the 12 volts to
give you a 24VC source. You can even add a pot where the
voltage-sensing wire senses the +3.3 at the motherboard end to get a
variable voltage power supply. And the PS specs require over-current
and foldback protection on all PC power supplies.

Put two in series (with careful separation of the grounds) and you're
up to+48 volts at many man y amps, at very low cost and weight. For
example, MPJA has nice brand new 180 watt supplies for $8.95 !!!

On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim

[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

"Ancient_Hacker" wrote in
oups.com:

In my experience, bench power supplies blow out about once a year.
Blown pass transistors, driver transistors, yuck.


Therein lies another nice thought. Lots of people use bench supplies, but
not everyone who does knows how to repair them. So if you find a decent one
broken you might buy it for peanuts and get it working. If you do, you'll
have learned a bit, and saved a lot.

"Jim Thompson" wrote in
message ...
On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim

[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Was it Ge or Si ?

"John Woodgate" wrote in message
...
In message , dated Tue, 8 Aug
2006, Mark Fortune writes

So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

You need more than 5 A AC to get 5 A DC. The rough rule is that a bridge
rectifier needs a factor of 1.6 times, but with modern huge filter caps,
think of at least 1.8 times. That's a BIG transformer, with THICK
secondary wire. Not a project to learn on, I would say.

It's not even easy to buy parts for transformers now. Maplin used to do
kits - bobbins, laminations etc. , but not now.

To learn about transformer design, you need a textbook and one of the best
is a classic - Radio Designer's Handbook, by F Langford Smith, which was
reprinted by Newnes (Butterworth-Heinemann/Reed) a few years ago. ISBN0
7506 3635 1.

Modern core material (silicon-iron) is better than the materials mentioned
in the book. You may be able to get the information on current materials
(maximum recommended induction, core loss power/kg, magnetizing VA/kg)
from the web.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

You can't beat a microwave oven transformer with a secondary transplant!

On Tue, 08 Aug 2006 21:19:21 GMT, "ian field"
wrote:


"Jim Thompson" wrote in
message ...
On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim

[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Was it Ge or Si ?


It was Silicon. I didn't use any Germanium power devices since I
boosted my car radio back when I was a junior in high school.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

I would look at cheap battery chargers.

Note that you can put the primaries in parallel and the secondaries in
series to get a higher output voltage by using multiple transformers. Check
phasing if you do this.

John Woodgate wrote:
In message , dated Tue, 8 Aug
2006, Mark Fortune writes


You need more than 5 A AC to get 5 A DC. The rough rule is that a bridge
rectifier needs a factor of 1.6 times, but with modern huge filter caps,
think of at least 1.8 times. That's a BIG transformer, with THICK
secondary wire. Not a project to learn on, I would say.

I think what you're saying is "try learning on some smaller transformers
first" I might just do that, cos it'd be a PITA if I screw up on a big
one and have to unwind it all again :]


It's not even easy to buy parts for transformers now. Maplin used to do
kits - bobbins, laminations etc. , but not now.

To learn about transformer design, you need a textbook and one of the
best is a classic - Radio Designer's Handbook, by F Langford Smith,
which was reprinted by Newnes (Butterworth-Heinemann/Reed) a few years
ago. ISBN0 7506 3635 1.

Thanks for the info, i'll try and get my library to order a copy.


Modern core material (silicon-iron) is better than the materials
mentioned in the book. You may be able to get the information on current
materials (maximum recommended induction, core loss power/kg,
magnetizing VA/kg) from the web.

I'll have a look, thanks

ian field wrote:

You can't beat a microwave oven transformer with a secondary transplant!


And I see plenty of old microwaves just laying out on the street
destined for the scrap heap around here. thanks for the idea.


Mark

Jim Thompson wrote:
On Tue, 08 Aug 2006 21:19:21 GMT, "ian field"
wrote:


"Jim Thompson" wrote in
message ...

On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:


What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim


[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Was it Ge or Si ?



It was Silicon. I didn't use any Germanium power devices since I
boosted my car radio back when I was a junior in high school.

...Jim Thompson

Correction: it _is_ silicon.
http://www.onsemi.com/pub/Collateral/2N3055-D.PDF.

Digi-Key has them for $2.10 a pop, in the TO-3 case, no less.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Tue, 08 Aug 2006 14:48:15 -0700, Tim Wescott
wrote:

Jim Thompson wrote:
On Tue, 08 Aug 2006 21:19:21 GMT, "ian field"
wrote:


"Jim Thompson" wrote in
message ...

On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:


What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim


[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson


Was it Ge or Si ?



It was Silicon. I didn't use any Germanium power devices since I
boosted my car radio back when I was a junior in high school.

...Jim Thompson

Correction: it _is_ silicon.
http://www.onsemi.com/pub/Collateral/2N3055-D.PDF.

Digi-Key has them for $2.10 a pop, in the TO-3 case, no less.

I said it was silicon. The Ge device I used in HS was a Delco
doorknob power device. I did 10W class-A ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Jim Thompson wrote:
On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim

[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.


They were, and were already pretty cheap. I used them at work in a big
current regulator in '74 or '75.

John Perry

"Mark Fortune" wrote in message
...
For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

So......

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

**** man! Switch that ****!

Nope, nothing else I can say without profanity.

SMPS, use a range of supplies, or just go SOL.

I mean, are you really planning on water cooling the maximum 600W you'll
dissipate? Heatsinks that size can get pricey. Don't say it won't happen
(the full dissipation).

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Jim Thompson wrote:

On Tue, 08 Aug 2006 14:48:15 -0700, Tim Wescott
wrote:


Jim Thompson wrote:

On Tue, 08 Aug 2006 21:19:21 GMT, "ian field"
wrote:



"Jim Thompson" wrote in
message ...


On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:



What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim


[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson


Was it Ge or Si ?



It was Silicon. I didn't use any Germanium power devices since I
boosted my car radio back when I was a junior in high school.

...Jim Thompson

Correction: it _is_ silicon.
http://www.onsemi.com/pub/Collateral/2N3055-D.PDF.

Digi-Key has them for $2.10 a pop, in the TO-3 case, no less.


I said it was silicon. The Ge device I used in HS was a Delco
doorknob power device. I did 10W class-A ;-)

...Jim Thompson

I was only taking issue with your tense -- the 2N3055, while venerable,
appears to be in current production. So it's an 'is' part, not a 'was'
part.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

In article ,
Mark Fortune wrote:
Is this even a feasable project to undertake (moreso on the money side
than timewise). Any other advice also greatly appreciated.

Put a search in Ebay and store that page. Keep looking - odd and large
transformers come up often, and go for quite reasonable prices. But what
you want (roughly) is common on large audio power amps, so shouldn't be
difficult to find.

Because of economies of scale buying the materials needed to make one will
cost you much more than a factory - and that's without the time and
difficulty involved.

--
*Don't worry; it only seems kinky the first time.*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Jim Thompson wrote:
What primitive semiconductors did you use in the output stage, or was
it a toob device? Did we have 2N3055s in '75? I don't memember.

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

Yup - Quad were using them in the 'late '60s in the 303.

--
*Be more or less specific *

Dave Plowman London SW
To e-mail, change noise into sound.

Do you need both + and - power at the same time? If not, just have 0-50V
would save you half the power.
If you need to use 1V at 5A, your power supply would become pretty
inefficient (supplying 5W and wasting 300W). Are you planning to fan cool
it? If not you need a huge heat sink.

If you use a switching design, it would be a lot more efficient.


"Mark Fortune" wrote in message
...
Greetings to the collective.

For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50) and
deliver up to 5amps of current. if my estimates are right i'll need a
600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had
a look at some transformers in this range, and they're a little out of my
price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Get a copy of the 1980 book:
Practical Transformer Design Handbook
Eric Lowdon
Howard W. Sams & Co. book publisher
ISBN: 0-672-21657-4

peter wrote:
Do you need both + and - power at the same time? If not, just have 0-50V
would save you half the power.

I would need the option of both +v and -v in respect to ground, but only
sometimes at the same time (ie when testing audio circuits, but not when
doing logic circuits) if I switched one of the secondary windings off...
would I still be saving half the power?

If you need to use 1V at 5A, your power supply would become pretty
inefficient (supplying 5W and wasting 300W). Are you planning to fan cool
it? If not you need a huge heat sink.

Wastage is becoming more apparent as I read more and more posts... and
am considering rethinking to a more energy efficient design now.

I was (originally) thinking big heatsink with some thermal controlled
fans screwed on.


If you use a switching design, it would be a lot more efficient.


switching psus I know nothing about, but think I will research this. Any
good places to start (apart from the obvious google)?

On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A


Well, it's theoretically possible to build a transformer from scratch,
BUT! You have to make a bobbin, find a lamination vendor that will sell
you only a few hundred lams, assemble the damn thing, hypot it, and
test it, to determine that you didn't get the lams tight enough so your
leakage inductance is unacceptable, redo it, redo the windings, interleave
the lams again, whack it a few times, pot it - - -

After about two weeks of this crap, you might want to go check surplus
dealers - they usually have surprisingly good bargains on transformere -
sometimes, you can buy them by the pound.

Good Luck!
Rich

Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Does nobody knows howto calculate transformers anymore?

this will be a 600Watt transformer

you will need iron of 150mm EEE and III (a standard dimension)
a form of 50x54mm

primary:
use 1.35mm diameter wire
roll 377 spirals

secondary:
use wire of 1.77mm diameter (if this does not exist, get the after next in
diameter)
weld first out line (60v)
roll 104 spirals
weld second out line (0v)
roll 104 spirals
weld third out line (60v)


put the irons one by one always alternate positions
tight as much as you can the irons
dive it into hot varnish and let it dry

this is just the transformer, i guess you will also want to pass AC to DC
and maybe a voltage regulator controlled by a variable resistor, but that
is another story


regards
ArameFarpado

On Tue, 08 Aug 2006 13:21:34 -0700, zekor wrote:
Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

I would recommend reading up from every source. I have built torroids
using the winding which was orginally a variac. These were 110 volt
units. You automatically have a primary so all you need to do is wind
the secondaries on top. I have also done the other type of transformer,
schelacing.the iron plates. I would also recomend what others have, buy
surplus on the market. Combine transformers if you can't find them.


I used to work for a battery charger manufacturer who made their own
transformers. They had a machine to stack the lams, alternating, of course,
and a big machine to spin the bobbin while the guy hand-wound the windings
on it. Then, when it was all stacked, they'd whack it to make sure all of
the lams were as tight as they could get them, bolt it up, hypot it, and
then bake them and dip them in hot varnish.

BTW, I don't think there are many USENETizens who would consider
themselves part of any "collective" - that's the Borg. =:-O

Good Luck!
Rich

Tim Wescott wrote:
Jim Thompson wrote:
On Tue, 08 Aug 2006 21:19:21 GMT, "ian field"
wrote:


"Jim Thompson" wrote in
message ...

On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:


What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim


[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Was it Ge or Si ?



It was Silicon. I didn't use any Germanium power devices since I
boosted my car radio back when I was a junior in high school.

...Jim Thompson

Correction: it _is_ silicon.
http://www.onsemi.com/pub/Collateral/2N3055-D.PDF.

Digi-Key has them for $2.10 a pop, in the TO-3 case, no less.

2N3055s are as common as 2N2222s. Salvage them from junked
supplies or amps, and the cost is nothing.

On Tue, 08 Aug 2006 22:53:34 +0100, John Woodgate wrote:

In message , dated Tue, 8 Aug
2006, ian field writes
You can't beat a microwave oven transformer with a secondary
transplant!

That depends on how the leakage inductance is produced, and whether you
can remove it, which you must in order to use it as a conventional
transformer

Taking out the old secondary is almost trivial, with a hacksaw and a
chisel. ;-)

But apparenlty, you need to add windings to the primary to bring the
magnetizing current down, or somethiing like that. I have an old MOT
that I've been experimenting with, and the idling current is just way
too much for any self-respecting 60 Hz trannie, albeit they do have
to account for the shunts, which current-limit the output.

On and off, I've been poking around with this thing, but now I'm at
a crossroads with it - do I cut it open, take the bobbin out, and
enhance the primary that way, or do I thread more #18 Formvar wire
through it until I build up another layer of windings? So far,
threading the new wire through has turned out to be much more of
a PITA than I had expected, so it's kind of on the back burner for
the moment.

Good Luck!
Rich

On Tue, 08 Aug 2006 23:26:31 -0300, YD wrote:

On Tue, 08 Aug 2006 13:52:26 -0700, Jim Thompson
wrote:

On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim

[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson

It's in my GE handbook from 1973. ISTR some magazine article from 1971
using it, but I'm not going up in the attic dusting off that pile of
old mags.

- YD.

I've run out of library shelf space, so I've been donating out of date
books (like "Mother of All Windows" for Win95) to charity book sales
;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Tue, 08 Aug 2006 13:52:26 -0700, Jim Thompson
wrote:

On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim

[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson

It's in my GE handbook from 1973. ISTR some magazine article from 1971
using it, but I'm not going up in the attic dusting off that pile of
old mags.

- YD.

--
Remove HAT if replying by mail.

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark


Look for a surplus transformer, you won't save any money trying to build
one yourself.

That's a BIG supply to be using a linear regulator for, I suggest
looking at some of the switcher IC's available now days, National
Semiconductor makes a series called Simple Switchers which are FAR
easier to work with than designing a switcher from scratch and they have
HV versions which are good to 80V or so.

Jim Thompson wrote:
On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:


What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim


[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson


Wasn't that around the time the Dynaco ST-400 came out? I rebuilt one of
those once, seems like it used a bunch of big Motorola power
transistors, I forget the numbers but they weren't 3055's. Seems like
there were 4 of each polarity per channel, or maybe it was 2, I do
remember the heatsinks were HUGE.

In message bqcCg.16233$l95.10256@trnddc08, dated Wed, 9 Aug 2006,
James Sweet writes

Wasn't that around the time the Dynaco ST-400 came out? I rebuilt one
of those once, seems like it used a bunch of big Motorola power
transistors, I forget the numbers but they weren't 3055's. Seems like
there were 4 of each polarity per channel, or maybe it was 2, I do
remember the heatsinks were HUGE.

Many manufacturers used 'custom' devices which were allegedly tested to
custom specifications by the device manufacturer. The Vcc max might be
higher than for the normal device, and/or beta range might be less.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

"James Sweet"


Wasn't that around the time the Dynaco ST-400 came out?


** 1973, according to this schematic:

http://www.audio-circuit.dk/Schematics/Dynaco_ST400.pdf



I rebuilt one of those once, seems like it used a bunch of big Motorola
power transistors, I forget the numbers but they weren't 3055's.


** Nope - more like the 100 volt, 200 watt, 30 amp MJ802 / 4502 devices.


Seems like there were 4 of each polarity per channel, or maybe it was 2, I
do remember the heatsinks were HUGE.


** The power devices were operated in *series* instead of parallel mode as
used in other high power amps. Made the Vcc and SOA requirements of the
output devices sooooo much easier.

2N3055s and the similar BDY20 appeared in the late 1960s, as did the RCA
38494 and 40411 used in the famous Quad 303 hi-fi amplifier.




........ Phil