On Friday 13 December 2002 06:23, you wrote: > Hi everyone, I have a couple of questions. > 1) Can the inputs and outputs of the L293 motor driver be connected in > paralell to increase the current output available? The motor I want to > drive would draw about 1 amp. more in peak (used in a small RC > car-turned-robot project).
I think that's a bipolar device - forget current sharing unless you want to get clever. You current share with fets. I would point you at some logic level fets, many of which are in nice small packs like the TO-251. If you start with p channel on top and n channel underneath, you might be able to tie the gates together and make a H bridge. > > 2) I just bought a faulty oscilliscope (model bwd 540 if that helps - quite > old...) which has a problem in the powersupply area, but control panel > lights still come on so I'm quessing its not the main transformer. There's > a smaller transformer (say 4x4x4 cm) which as far as I can tell is the > source of a buzzing/spluttering sound when powered up. It outputs several > different voltages, 2 or 3 are around 15 to 30v, one is 4.5Kv and one is > ~1.5Kv (fortunately I have a service manual for it). There was a 2200u, 25v > cap in the rectification part of the low voltage outputs which has some > crusty blue stuff around the terminals and had a very low resitance > (something like 150 or 200 ohms instead of the 500-odd Kohm of the > surrounding caps). I replaced this but to no avail, so my conclusion is > thus : the cap dried up and caused a short in a particular transformer coil > which > took out one or two of the others, perhaps one of the high voltage ones and > this is now arcing. So what can I do to fix it from here? Does it sound > like I've tracked down the problem correctly? I really need an oscilliscope > to fix it... Overloaded or blown transformers rarely talk, but do heat up and smoke. Putting this politely, I don't think you know how to approach this. I would disconnect rectifiers, and verify the transformer; then put them back (check they're good) and disconnect feeds out of the psu board and switch on. Your buzzing/sputtering may well be the electrolytics some of which which leak noisily after long periods without use. Leave it 20 minutes, and then replace every one still complaining if they don't fix themselves. Then add back your loads (LV first - HV last), check currents, and start tracing from there. I'd circle around the 4.5Kv very carefully - it will blow any normal meter away. -- Regards, Declan Moriarty. -- Author: Declan Moriarty INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
