Aurex (Toshiba) SB-A10B

The ever-cheerful Matin's been badgering me to do a couple of amps for him, a beautiful Luxman R-1040, and an awful Aurex SB-A10B ... he's off on holiday, so dropped them off on his way past...

The label helpfully has the fault description "As they say in Brum, it woo gooo!" which roughly translated means it's doesn't work.

Fancying a quick win before tackling the enjoyable, but somewhat arduous task, of re-capping his Luxman, we'll have a quick look.

It's one of those small form factor separates, and quite well regarded (by those who don't have to fix them) Aurex was Toshiba's "posh" range of hifi.

Something's nagging me in the back of my mind, that last time I did one of these it didn't end well... 

The first challenge is to get the damn thing apart. Remove the Bass, Treble and Volume knobs, and every damn screw you can see... there are plenty. Don't forget the two recessed ones.

Now start wiggling the case around until frustration builds to an almost intolerable level. 

Eventually the top should "ease" forward. Not much room in there....

We need to get the bottom off now....

.. and at this point it's worth noting that the service manual tells lies. At no point does it mention that you need to remove this screw. Remove it. 

Now spend another 5 minutes wiggling the case like a demented fool, only to discover you can't until you remove the two plastic tubes that surrounded those two recessed screws from earlier.

... remove the two plastic tubes, take a deep breath and start wriggling the case like a Tory MP in front of a select committee, until it finally yields. 

You are now faced with a densely packed lump of electronics. Complete with surface mount resistors (in 1979!) ...

The mains fuse is located under a small plastic cover by the on-off switch. It's visibly blown, and looks to have failed with purpose.

It's a T1A fuse, and is duly replaced.

Voltage is gently increased on the variac, whilst monitoring the current, and it's very clear something is under a lot of load. 

Measuring the output transistors on the left channel, and all is well... measuring the right hand channel and the output transistors (2SB595 and 2SD525 respectively)  are short circuit, well bang goes my quick fix... and they're made from unobtainium (enter the whole of the internet saying they're still available on eBay, off you go and order them then, good luck if they're shot or fakes). Great. 

Some discussions are had with Martin, ruining an otherwise pleasant holiday no doubt, and I reckon an MJE15030 and MJE15031 will do as sunstitues, so some are ordered from a reputable supplier. I will not be beaten by mere machinery. 

I have, however, got an awful sinking feeling... 

... eventually the Luxman is finished (phew!) ... so it's back to this ... 

The heatsink and output transistors are removed as one piece... Both transistors are lose on the heatsink! No small wonder they failed.

The NPN device has been especially warm!

Look at the state of the insulator! We'll have a nice new one.

The MJE15030G and MJE13031G substitutes are pressed into service, after checking the driver transistors are undamaged, which they are...

Both channel's screws are locked into place with a dab of thread lock.

The unit is lashed up naked on the bench, and power is supplied gently via the variac ... after a few seconds the speaker protection relay clicks, indicating there's no DC on the speaker outputs.. Good.

The bias is set up as per the service manual, and speakers connected up... 

... and knock me down with a feather, it all works and sounds great! It's left on test for a while playing The Lasters by Fred Deakin. 

Now the fun and games shoehorning it all back into the case...

... and after much cussing and swearing ... 

... another saved from landfill!