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Woodburner

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  1. Have finally managed to find LM7812, and mine are definitely not that. :) The mystery transformer component was a thermal protection switch, and I'm hoping the by being careful and not overloading it, the transformer will be fine without it. In fact most things are sorted, the main sticking point is not knowing what rating of bridge rectifier I need. I have two in my box of bits, but apart from the 'forward voltage' I have no idea what rating they are.
  2. I have a bunch of these: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=641-730&x=0&y=0 I see the numbers 78 and 12 in there. Is that the 7812 you mean, pyrohaz? Seems like one of those should do the trick for the circuit and fans anyway.
  3. I can't get a 7812 anyway. I found this though. http://www.maplin.co.uk/Module.aspx?ModuleNo=8063 Will that do the trick? ETA: Found the proper setting for the meter, and it reads fairly steady at a bit over 12.8V. :)
  4. Maplin's don't seem to do the 7812, would this do instead?
  5. Have removed the defunct whatever, and now the voltage appears to go up and down. Figured that's something to do with it being AC, and hooked up a lamp, to check. Lamp stays nice and bright, no ups and downs, so when the shops open I'll nip out and see if I can get a suitable rectifier, and a 7812. Many thanks. :)
  6. Hi pyrohaz, Thanks for replying. :) I can see quite easily on both transformers which coil is which. It looks like the output coil on the 72VA one may be shorted, after all, as it only measures minusculely more resistance than the meter's internal resistance. :( The winding is really thick wire though, about 2mm, so I wouldn't expect much resistance, but I don't know diddly. :-\ The other one has kind of multiple windings for the secondary coil, with half a dozen wires coming off, each marked with a different voltage, from 0(!) to 30. They are much thinner wire, which may explain why they do show slightly more resistance, (increasing with each additional coil). I think I'll try replacing the rectifier, now that I know what it is, hopefully the 'bloke in the shop' will be able to find me the right one, thanks. :) Is it normal for it to be on the + side of the input? You say they are usually for high voltage, so I presume it is ok? Most of what you've said about rectifiers is unfortunately over my head, but at least you've put me on the right track. :) Thanks too, for the regulator chip number. I should be able to use that to protect the thermostat circuit, and maybe the fans? (PCU case fans 2off). I may be getting ahead of myself here, but would it be possible to leave the bulbs (heat source) on 12V AC and just rectify the input to the circuit (and fans?) ? (The heat source is connected by a relay, operated by the circuit.
  7. Hi everyone, I need a 12v 5A supply to run an incubator. I've made up Ron J's thermostat with appropriate resistors, and while I could run that with his transformerless power supplly sircuit, I really want the heat source and fans to run at 12V too, and that needs more amps. I thought I had a suitable transformer, rated 72VA 12V, (I found it in Dad's shed - Dad was a Marconi's research engineer ;) ), but when I tested it (with a meter), it shows 12V to start, but dies rapidly. I can't see anything wrong with the coils so presume that the one and only component (rectifier? it's Russian) is the problem. Would it be possible to fix/replace this? I am on a tight budget, so can't afford to buy a complete new power supply. I couldalso use some general information on transformers, and especially on rectifiers, and voltage regulation, or w/e it's called, too, as I have another tranformer, stripped of everything except the input and output wires. :-[ Thanks for reading this. :) Hope you can help. :) :)
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