6v & 90v DC Power supply
in [Design]
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From: Joerg on 27 Dec 2005 13:59 Hello Jim, > Do it the way the original radio did it -- dynamotor. You can still find > them in the back room at a lot of military surplus electronics junk stores. > But then be prepared for some major restoration. The bearings of a lot of these are nearly shot, mostly from sitting in an attic for decades. It's like old pond pumps. They run fine for a few weeks and then the racket increases, some weird noises appear, things get hot and they seize up. I restored an old Hammond organ. These generate the tones in a similar manner. A motor (plus a start motor) and over a hundred pickup coils on the long secondary shaft. 20 hours of hard work got it going again but we have accepted the fact that some of the bearings are pretty much over the hill. So it needs 2-3 starts to coax it to run without that mild screeching in the background. Getting spare parts from a company that went out of business 30 years ago just isn't going to happen. Regards, Joerg http://www.analogconsultants.com
From: David Harmon on 27 Dec 2005 14:22 On Tue, 27 Dec 2005 05:58:18 GMT in sci.electronics.design, john_c(a)tpg.com.au (John Crighton) wrote, >This link tells you how to use the TL494 IC >http://focus.ti.com/lit/an/slva001d/slva001d.pdf So why is the guy from TI showing NTE transistors for the power switching? Nothing in the TIP line good enough?
From: Rich Grise on 27 Dec 2005 16:03 On Tue, 27 Dec 2005 18:59:56 +0000, Joerg wrote: > Hello Jim, > >> Do it the way the original radio did it -- dynamotor. You can still find >> them in the back room at a lot of military surplus electronics junk stores. > > But then be prepared for some major restoration. The bearings of a lot > of these are nearly shot, mostly from sitting in an attic for decades. > It's like old pond pumps. They run fine for a few weeks and then the > racket increases, some weird noises appear, things get hot and they > seize up. > > I restored an old Hammond organ. These generate the tones in a similar > manner. A motor (plus a start motor) and over a hundred pickup coils on > the long secondary shaft. 20 hours of hard work got it going again but > we have accepted the fact that some of the bearings are pretty much over > the hill. So it needs 2-3 starts to coax it to run without that mild > screeching in the background. Getting spare parts from a company that > went out of business 30 years ago just isn't going to happen. So, put the cam thingie on some sort of spindle, with some kind of depth gauge thingie, (maybe a slide pot and a stick), and map the disks, and just make the same waveform from ROM? Good Luck! Rich
From: Joerg on 27 Dec 2005 16:27 Hello Rich, >>I restored an old Hammond organ. These generate the tones in a similar >>manner. A motor (plus a start motor) and over a hundred pickup coils on >>the long secondary shaft. 20 hours of hard work got it going again but >>we have accepted the fact that some of the bearings are pretty much over >>the hill. So it needs 2-3 starts to coax it to run without that mild >>screeching in the background. Getting spare parts from a company that >>went out of business 30 years ago just isn't going to happen. > > So, put the cam thingie on some sort of spindle, with some kind of > depth gauge thingie, (maybe a slide pot and a stick), and map the > disks, and just make the same waveform from ROM? > That has been tried many times. Several rather expensive electronic organs have come out claiming to emulate a Hammond. So far the real enthusiasts do anything to get their hands on the real thing, knowing that there will come a day when the last one croaks. IIRC it was Paul Shaffer (the guy who makes the music at david Letterman's show) who spent the equivalent of a luxury car to have one restored. Regards, Joerg http://www.analogconsultants.com
From: James F. Mayer on 27 Dec 2005 18:02
"David Harmon" <source(a)netcom.com> wrote in message news:43db1d39.145554171(a)news.west.earthlink.net... > On Tue, 27 Dec 2005 05:58:18 GMT in sci.electronics.design, > john_c(a)tpg.com.au (John Crighton) wrote, >>This link tells you how to use the TL494 IC >>http://focus.ti.com/lit/an/slva001d/slva001d.pdf > > So why is the guy from TI showing NTE transistors for the power > switching? Nothing in the TIP line good enough? > > Probably good enough for his measly 32 volts. I need to modify that circuit to work on outputs of 90 volts and 6 volts. |