Building a transformer
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From: Jim Thompson on 8 Aug 2006 16:37 On Tue, 8 Aug 2006 20:51:44 +0100, John Woodgate <jmw(a)jmwa.demon.co.uk> wrote: >In message <qI-dnR0veMUYQkXZnZ2dnUVZ_radnZ2d(a)insightbb.com>, dated Tue, >8 Aug 2006, t.hoehler <t.hoehler(a)insightbb.com> 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 Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: RST Engineering (jw) on 8 Aug 2006 16:44 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.
From: Ancient_Hacker on 8 Aug 2006 16:50 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 !!!
From: Jim Thompson on 8 Aug 2006 16:52 On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)" <jim(a)rstengineering.com> 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 Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Lostgallifreyan on 8 Aug 2006 16:57
"Ancient_Hacker" <grg2(a)comcast.net> wrote in news:1155070223.658521.134190(a)h48g2000cwc.googlegroups.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. |