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Technics SU-X301 Amp - repair or replace?

dadgad

dadgad

pfm Member
For a number of years I've used this late 80's amp (that came from my late FIL) for stereo sound from my Sony TV system. It has worked very well driving my original Linn Kan Mk1's and has lots of handy features including multiple inputs and a quick muting button. It recently refused to switch on again following a couple of power outages (including one where the electricity supply 'flickered' in a way I'd never seen before, for at least 20mins!).

I figured there might be an internal mains fuse that could have died and investigated. Sure enough there was, and I spent a little time decoding the various stripes on it and identifying replacements. Sadly, on replacing the fuse and connecting to the mains, switching on provoked a pop and a puff of smoke from the fuse. So something has shorted inside the amp I guess and at this point my expertise runs out. Can anyone advise on my next course of action? Local electrical repairs shops are largely closed (and tend to advertise 'fixing your toaster' etc), and while I'd happily ship it to someone more specialist for repair I wonder if that might take more time/cost than its worth.

Here's a pic of the amp, with more to follow:
DSC-0137.jpg
 
Here is a picture of the interior of the amp. The mains input is on the bottom RHS, and there is also a mains output for linking the amp with other components:
 
Here is the fuse that came out, and a box of the replacements I bought showing the spec:
 
Bin it. Personally I'd rescue the mains transformer for possible future use first. The fault is that black module bolted to the heatsink which is pretty much unobtainium and if you can find one likely to be twice the value of the amp.
 
If you're limited in diy knowledge probably not brst to mess with mains electricity. Nothing looks blown on the main board, so it's likely something between the inlet and transformer output.

Looks like there's some sort of varistor, gold disc, on that board where the mains wires, blue brown terminate.

Possibly an easy job for someone with multimeter and a variac or maybe even a bulb tester.

Or as Jez says it could be the output device
 
As Arkless said, most likely the power amp module. They have a tendency to fail short. I’m not familiar with that particular amplifier but it will most likely have a Sanyo stk module as the amplifier? These tend to get a bad reputation but I’m almost certain it’s down to inadequate heatsinking. Every amp I have come across with these amp modules have poor heatsink design. I can imagine if the module is removed and fuse replaced the amplifier will probably power up? You can buy replacement modules but they will almost certainly be fakes or parts pulled from scrap units. Probably better and more cost effective to replace the amplifier?
 
Years ago I had a Technics amplifier that I sold to a friend - just before the output module shit itself. I found a cheap Rotel RA-820BX for him so all was well again!
 
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