Circuit diagram needed for Durst power supplies EST 301 and EST 450

Quote:

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Originally Posted by macmicus

Paul Ron,
it is difficult to determine the cause of such a load on these resistors without the circuit.

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it is hard to see whats going on with your board n even more difficult since i was looking at the wrong pictures posted in this thread. i see the burnt resistors in your photo are the large ceramics. the rectifiers look good... i do see an optocoupler n a relay on your board... but neither have any indication of overload although that doesnt rule them out yet.

most times optocouplers n relays will only cause symptoms, not fry circuits when faulty. shorts, bad solder at hot points like those big resistors and ac to dc conversions in power circuits do fry. btw it may be just that over the years those hot resisors deteriorated the solder and new resistors n redoing those burnt traces just may bring that board back to life. ive seen this so many times in old tube tvs n radios.

post better pix of both sides of the board so we can trace it out n maybe get a better idea whats feeding those resistors... it would help to know where the mains come in? if you can figure out where outputs n inputs go so we can reverse engineer it?

btw who has the bad board? jvelez or mcmicus or both?

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These photos are after replacing the electrolytic capacitors and two power resistors.

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did you restore the traces from the power resistors? just jumper it with wire. the burnt traces will cause increased resistance n just fry again if they arent completely fried.

ill assume you checked the polarity of the electrolytics.

Check the tantalum capacitors (the blue water drop shaped ones) for shorts. Tantalum caps often develop shorts.