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Thursday, 14 December 2017

Sharp Optonica SM-5100 integrated amplifier repair.

Colin wondered in ....

"Got this old Sharp amp, smoked last time it was switched on. Can you take a look?"

Yeah, why not....

It's from the unfairly overlooked range of Sharp Optonica hifi, an SM-5100. Optonica was a sub-division of Sharp, primarily to complete with other manufacturers high-end brands such as Panasonic's Technics.


Nice slender looking thing.... dating from the early 80's.


Removal of the top panel (not as easy as you'd think, it's a very tight fit!) reveals the culprit, the dreaded Rifa X class filter capacitor... in this case it's 0.0047uF 275VAC and X2 rated....









... which is soon evicted and replaced with a nice Vishay one.. again X2 rated. The X2 rating is crucial in this application.










Powering up and there's no smoke. There's also no output from the left hand channel. Pots and switches are all cleaned up to no avail...










After a little bit of head-scratching, and in fear of one of the STK-0050II output modules having failed (replacements are still available, but many are turning out to be faked, and either don't work or fail rapidly) RLY501, the speaker protection relay is found to have failed. A suitable replacement is sourced and fitted.



There's a good range of input and output sockets, two tape loops and a pre-amp to power amp bridge.

Two sets of speakers are catered for.

Look at that nicely shielded toroidial transformer.




The mains lead is replaced, at someone had cut it short at some stage, and fitted one of those daft "Masterplug" things with the tiny round pins.

It performs very well. Outputting a very reasonable 35W in 8 ohms. The phono stage is very quiet.

The amp is soak tested with "Upstairs at Eric's" by Yazoo, an album I never get tired of :)

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