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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Incase the poster a couple of weeks ago is still here.
I mentioned in that thread a phone call from someone , who has now brought his in . He leant it to a "girlie , so of course she has no idea what she did wrong". I had previously covered that Yamaha booby trap of chromed steel handle with nylon spiral wrap and covered the boobytrap metal elbows of the short speaker lead for integral speaker, with heat shrink - so what did she likely do ? All she did was use a pair of extension speakers plugged into those plastic outlet sockets. I had previously repaired this, nice to know bulk standard IRF740 instead of near unobtanium ST P14NF12FP 120V 14A , and awkward 6x3mm 0.056R 1W SMD R/fuse replaced with with mica protected 2x 15mm long pieces of 8R/metre resistance wire are functional replacements (perhaps 2 years of weekly gigs plus rehearsals). That amp is fine , the other one blown this time. Cold testing the original powerfets seem ok, one of those R3134 SMD .056R o/c with a pock mark blow hole and a load of mysterious grey plastic and cotton wool laying about. Exploded C2121 22uF/50V SMG (M)85 deg C electrolytic. Have to explore a bit further around that R and C for possible other colateral damage, before powering up with replacements |
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I took another opportunity to search these pa boards for the difference , ie
an antiphase pinning or device. Nothing found again - anyone know the secret of the difference between boards 6479e the inner amp, and 6479b the outer one ,or even whether you can safely swap them around . As long as one of each designation |
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