Building a transformer
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From: James Sweet on 8 Aug 2006 23:14 Jim Thompson wrote: > 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 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.
From: John Woodgate on 9 Aug 2006 02:10 In message <bqcCg.16233$l95.10256(a)trnddc08>, dated Wed, 9 Aug 2006, James Sweet <jamessweet(a)hotmail.com> 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
From: John Woodgate on 9 Aug 2006 02:17 In message <44d92793_2(a)x-privat.org>, dated Wed, 9 Aug 2006, ArameFarpado <a-farpado.spam(a)netcabo.pt> writes >Does nobody knows howto calculate transformers anymore? > >this will be a 600Watt transformer Does nobody know how to calculate rectifier circuits any more? This will need to be a 900 W transformer. -- 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
From: Phil Allison on 9 Aug 2006 03:00 "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
From: John Woodgate on 9 Aug 2006 03:48
In message <4jtfg7F9hi9fU1(a)individual.net>, dated Wed, 9 Aug 2006, Phil Allison <philallison(a)tpg.com.au> writes >RCA 38494 and 40411 used in the famous Quad 303 hi-fi amplifier. 38494 is a custom part number, but 40411 looks like a standard part. What substitute devices are used for repairs? My 303 suffered its second elco failure recently, and an elco in the 33 preamp came out in sympathy. Coincidence. Of course, I put new elcos in both channels. -- 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 |