Rik wrote: Hi Rik, Thanks - I found the schematics via Wikipedia (of all places); and the text file too (can't remember where that was linked from). blown; the question is, where the heck would I get one of those from?? Here's the pin-out (from the solder side, heatsink towards you): 240v o o 0v 240v o o 0v n/c o o 0v o 0v n/c o o 12v o 12v 0v o o 12v 0v o o 12v Yes, there are two additional pins stuck out of the side; it looks like the taps have been taken out separately. The 6 0v/12v connections are a guess, based on the fact there are pins, and they're soldered into the same pads as the outboard 0v and 12v. They may, of cours, all be n/c Also, 0v is not *really* 0v, given that there's AC going in; except that it's already been through a rectifier, which seems odd to me. Is this something to do with it being a switching PSU? I could fabricate an entirely new PSU, or even hacksaw up a PC supply (an old AT type with a physical on/off switch) to go in this one's place; but it'd be nice to keep it reasonably authentic. Cheers, Ade. No virus found in this outgoing message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.24.1/1469 - Release Date: 27/05/2008 13:25

Hi Ade If it is a switcher, it sounds like you don't understand how these work. Please send a pointer to the schematic you located. We can then talk about failures in switchers. Dwight _________________________________________________________________ Give to a good cause with every e-mail. Join the i?m Initiative from Microsoft. http://im.live.com/Messenger/IM/Join/Default.aspx?souce=EML_WL_ GoodCause

I don;'t know of any useful on-line info. There's a pretty poor article in this month's Elektor magazine (which might give you some idea), and there's a reasonable description in the _second edition_ of The Art of Electronics (a book which you ought to have anyway...) -tony

Hi First, I agree with Tony, the transformer is most likelty OK. Your earlier description wouldn't be enough to say it was good or bad. Measuring things on the primary side with a scope would be difficult without using an isolation trasnsformer. The point in the circuit that you'd need to use as ground reference has about 150-170 volts DC on it. If you connected the scope ground to this point you'd really blow things without using an isolation transformer. Next is that T3 is a pulse transformer and not an 60Hz AC transformer. The input is from the regulator chip, pins 8 and 11. One should see a 50-150KHz pulse on these pins. This would be the first place I'd look. Dwight _________________________________________________________________ Keep your kids safer online with Windows Live Family Safety. http://www.windowslive.com/family_safety/overview.html?ocid=TXT_TAGLM_WL_Re…

---snip some --- Hi Ade No, Q1 is on the secondary side of T3, not the primary. IC1 generates the pulse that go through T3 and cause Q1 to turn on for the short pulses. I'll try to walk you through how this particular supply works. ---snip-- some more It is unlikely that you'd see anything more than a small spike on a scope The T1 seems to have about a 100:1 ratio or more. Let me try to describe how this supply works. This should help you fix it. First, T2 provides power to IC1. IC1 monitors the 12 volts out through R14, VR2 and R12 network. If it is more than 12 volts, IC1 will sorten the pulse on time to T3. If the voltage is too low it will increase the pulse width. The other components around IC1 provide time constants for the pulse frequency and filter of response time of the regulation. IC1 also has a current monitor that looks at R11. If the voltage across R11 is too high it will turn on a circuit to stop the pulses to T3. Now, lets look at the high voltage side. As Tony has stated, you can't see much on a scope because of the fact that everything is following the ac input. Where you'd want to connect the ground would blow a fuse, unless you ran differential or as I suggested, use an isolation transformer. First the input AC goes through the filter network of L1 and some capacitors. It then goes through a full wave rectifier, causing a DC voltage to be developed on C7. You should measure this voltage with an ungrounded meter. You should see about 300volts across C7. If not, something is open in the input circuits. If, as you say, you see pulses on T3's primary side, it must be in the bridge rectifier is open. The voltages measured relative to ground have little meaning. T3's secondary is connected to the emitter and base of Q1. The pulse will cause Q1 to turn on for a short time. Since this is a short pulse,T1's secondary will see a voltage spike as well. This will forward bias the leg of D6 from the transformer to L2, charging C14. When the pulse is gone on T3's output, Q1 turns off. This turns the top leg of D6 off. Because some energy is now stored in L2, the bottom leg of D6 will now conduct, further charging C14. It is this voltage that feeds back to IC1 to change the pulse width going to T3 and on to Q1. This completes the 12 volt part of the supply. The 5 volt output is completely supplied from the 12 volt line. If there is no 12 volts, there is no 5 volts. The 12 volts powers IC2 that sets the regulation of the 5 volt output. It is directly connected to the transistors that switch the DC from the 12 volt line to the 5 volt. IC2 turns on Q4 and Q3 for a short amount of time. This causes current to flow in L5 and charge C21. When IC2 turns off Q4 and Q3, L5 will still have some stored energy, causing D7 bto conduct, further charging C21. IC2 monitors the voltage and adjust the pulse width to keep the output at 5V, in the same way as IC1 did. Besides testing the voltage across C7, as I suggested earlier ( being very careful not to electricute one self, you might also unsolder Q1 and see if it is shorted. This supply is also unique in that the 5 volt part runs from the 12 volt side. It would be possible to connect a 12 volt bench supply to the 12 volt output leads ( with the mains not connected ) and see if the 5 volt output works OK. That is all I have for now. Dwight _________________________________________________________________ Change the world with e-mail. Join the i?m Initiative from Microsoft. http://im.live.com/Messenger/IM/Join/Default.aspx?source=EML_WL_ChangeWorld

Hang on a second... Why do yuo think the transformer is the problem? This sounds like a switch-mode PSU. And while transformers can and do fail in those, it's not at all easy to diagnose the fact. They normally have windings witha very low DC resistance and will test as a dead short on any nornaml multimeter. Most of the time, when a SMPSU blows its fuse violently, one of the power semiconductors, often on the mains side, has gone dead shoirt. If you're lucky, a rectifier diode. If you're unlucky, the chopper transistor, which has possibly been damaged by a failure in some other component (that's why I said 'unlucky -- if you just replace the transistor, the new one will most likely fail again at switch-on). In this case, a replacement fuse held, which makes me suspect that some other component in the mains circuit has filead open-circuit. Maybe a current sense resistor or a surge-limiter thermistor, or...

Tony Duell wrote: OK, the reason I suspect a transformer; there's power getting as far as the primary windings of the transformer (can be seen on an oscilloscope); and it seems to conform to the "chopped" DC that I now know a switcher expects. All three transformers are fed mains from the same place: T3 has an output voltage, Tunnamed has an output voltage, T1 has no output at all - not even noise. The output of T's 1 and 3 feed into the 12v board; one side is OK (from T3), the T2 side has nothing. Although I would normally agree with you, in this case I'm pretty sure the electronics prior to the transformer are OK - witness the power coming through T3. I can only assume that the primary winding of T1 has failed; but I've not yet removed it from the board to test it in isolation. Cheers, Ade. No virus found in this outgoing message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.24.2 - Release Date: 28/05/2008 00:00

After working on a SMPSU (or any power supply for that matter, but especially a switcher), I usually power it up to test throught a light-bulb. At first with no load and a low wattage bulb (40w) - Most switchers won't run with no load, but you will see the bulb pulse is it kicks - Brightly and solidly lit = investigate further. If it passes that test, move up to a 100w bulb and just enough load to get it to regulate. This is assuming a small (50-100w supply) - if it's a big monster adjust your "current limit" accordingly. Has saved me from "secondary catastrophic failures" on more than one occation. Dave -- dave06a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.classiccmp.org/dunfield/index.html

On Thursday 29 May 2008 16:29, der Mouse wrote: This is more than just talk, they put it into law: http://billstclair.com/blog/kiss_your_bulbs_goodbye.html Idiots. :-( -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

On Friday 30 May 2008, Tony Duell wrote: I don't see what the problem is. There are much more efficient methods of lighting, than the one that Edison worked a lot on over 100 years ago. In addition to compact fluorescent lamps, you can get LED-based bulbs, halogen lamps (which still are effectively incandescent, but a bit better), and various gas-discharge lamps. I don't think I've ever seen a CF that had a ballast that operated at mains frequency. Usually, a switching supply that runs at many kHz. Normal fluorescent bulbs, with a "magnetic" ballast instead of an "electronic" ballast, though could produce your 50Hz flicker. CF bulbs would need do be quite a bit bigger and heavier to have a 50/60Hz ballast in them. Between that, and the phosphor persistence of the bulb, I don't think this could be a real problem. If it is, you could always just run a fluorescent bulb off of a DC supply. :) LED lights turn off much faster than Incandescent bulbs do. Plus, it's easy to get/make one that produces red light. :) Halogen? There are fairly good spectrum flourescent bulbs available these days, but I've not tried to look at them through a prism. Halogen? Maybe a properly engineered RL circuit instead of some cobbled-together light-bulb current limiter. :) Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

On Friday 30 May 2008, Tony Duell wrote: But they are generally not (AFAIK) covered by bans. The only bans I know of apply to standard edison-base type incandescent lamps. Halogen w/tungsten filament lamps aren't included. And, I don't think anyone is considering a ban on incandescent automotive headlamps, either, for example. I think you missed my ":)". Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

Actually, this reminds me of another application... the audio oscillator. As is well-known, it's very difficult to make an adjustable LC oscillator at audio frequencies. An RC oscillaotr is possible, but stabilising it (so you get a reasonably non-distorted sine wave output) is the problem. Now many yeats ago, a guy working for Prof Terman (you do know who I mean, right...) solved this problem. He used a Wien bridge circuit as the 'resonant element', in the feedback loop of a *3 amplifier. The gain of the latter was stabilised by a light bulb as a non-linera resistor with just about the right time constant. Anyway, I read somewhere (possibly in one of Bob Pease's columns) that somebody had tried to improve upon this circuit using a more modern approach, an FET to cotnrol the gain, a carefully-designed control loop, etc. The result was a an oscillator with a more distorted output than the simple light-ulb-stailised one... -tony

Tony Duell wrote: This particular subject is near and dear to my heart. The incandescent light bulb linearization technique is attributed to Bill Hewlett, and was presented in his Master's thesis at Stanford University in 1938. The design was commercialized into Hewlett-Packard's first product, the model 200A audio oscillator, in 1939. (was Hewlett studying under Terman at the time?) Later, well-known analog electronics god Jim Williams (staff scientist at Linear Technology) developed a modernized equivalent of that circuit which actually does manage to outperform it by a considerable degree. It uses several very high-tech op-amps, along with an analog optoisolator (an LED optically coupled to a CdS photocell), in a fairly elaborate circuit. It is far, far more complex than Hewlett's original oscillator, but it does work amazingly well. Williams presents this circuit (and many pages of very interesting reading, as he describes the process by which he arrived at his final result...ideas, testing, failures, successes, optimization, etc) in the absolutely fantastic book entitled "Analog Circuit Design: Art, Science, and Personalities". I strongly recommend that book. Bob Pease may have done something like this, but I suspect you're thinking of Jim Williams' work. -Dave -- Dave McGuire Port Charlotte, FL

Tony Duell wrote: I can also recommend the book. I have a copy that I got, I think, probably remembers that one). I can also recommend the other books in the EDN series, The Art And Science Of Analog Circuit Design, by Jim Williams and Troubleshhoting Analog Circuits, by Bob Pease. -- John Honniball coredump at gifford.co.uk

On Saturday 31 May 2008, der Mouse wrote: If you're worried about a ban on incandescent bulbs for the purpose of current-limiting device, then stockpile a bunch of them for your own use. It's not like you're going to go through them quickly in this application. I think that the power savings is worth the annoyances of a ban. Halogen bulbs do. Not from what I've seen. ISTR that halogen bulbs are actually more efficient in lumens/watt than a "standard" incandescent bulb. A "ban" such as those proposed is only a ban on sales of new bulbs, not on *using* them... Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

On Sat, 31 May 2008, der Mouse wrote: And one thing to keep in mind: Incadescent bulbs consist of glass and metal, whereas gas discharge lamps like the CFLs contain lots of mercury and other very dangerous things and must be disposed of as hazardous waste (not even just electronic waste!). Another thing: CFLs need a so much higher energy effort during manufacturing than ordinary light bulbs. The latter can be built at one place, the former needs electronic components (mostly from China, consider the energy required for their production), a PCB (energy? toxic waste?), mercury (!!), a fluorescent glass coating (toxicity?), a plastic housing (petrol based, recycling?), and so on... And consider the energy and effort needed to recycle all these things. And: LEDs aren't so much better in this context! What has never been published (surely for the fact that the CFLs would be considered much worse than light bulbs...) is the total toxicity and energy balance from manufacturing of either lamp until its final disposal... So much for this off-topic thread... I wouldn't consider replacing the optical transducer lamp with an LED... Christian

Roy J. Tellason wrote: Incandescents make great dummy loads for transmitters. CFL's decidedly do not. etc... Another problem with CFL's is that they are very risky in explosive and combustible atmospheres than incandescents. There are sealed light fixtures for incandescents but they are not approved for use with CFL's. Some CFL's, perhaps all, will not fit in the incandescent fixtures. CFL's may also be too hot for such sealed fixtures. And another problem is that CFL's cannot tolerate shock & vibration anywhere near to the degree that incandescents can. There are fluorescents specifially designed for vibration but they are expensive as hell and they are not CFL's. In a recent 1.0 quake on an unknown fault, all the CFL's broke in an office building less than 1/2 mile And yet another problem is that CFL's cannot tolerate the high temperature environments that incandescents can. There are fluorescents specifically designed for this, too, but they also are very expensive. Oh, I think this might be a problem too: The color and color temperature of CFL's is not consistent even within lots and there is frequently UV leakage, especially among the imports (yeah, like Chinese imports). For some imaging apps, this is intolerable. Requires the lamps be replaced with very expensive lighting systems like gas discharge lighting. Or requires time-wasting constant color adjustments, etc, adn. Most incandescents used in imaging have known colors and color temperatures and any changes over the bulb's lifetime are predictable. Ever put a CFL on a microscope, replacing the halogen lamp? Doesn't work very well. It's impossible to get a good parallel light onto the work. This is for inline lighting, with the lighting done through the optical path, not the external illuminators. == jd