Repairing Wharfdale SPC 10 Active Subwoofer

tldr: Skip to video by Silvestron and read ‘The problem I ran into section’ below. My dead subwoofer is now working.

We bought the SPC 10 subwoofer as part of a Diamond 5.1 speaker set around 10 years ago – was a lot of money. Noticed the other day the bass sounded a little flat. Turned out the SPC 10 ‘power cube’ was not coming on (no little green light on back).

Started by checking fuse which is mounted in main input on back of unit (New Zealand version anyway) – that was fine.

Ignoring warning on the back I opened the unit to see if I could see anything obviously wrong:

  • The IC connected to big aluminium heat sink on high voltage side of power board was blown. I was unable to read lettering on chip since burnt off/ blown away.
  • The power unit was not supplying low voltage (15V) to the processing board.
Blown IC

What Google said

A saviour – Silvestron Bits and Bytes video

Resigned to the thing being totalled and that I would be having to lob into the sea (has a symbol on back warning against putting in dustbin) I came across video below.

The chap had same issues as I (blown IC and no low volt power) but was able to identify the blown IC chip: a TOP261YN by Power Integrations.

Luckily Silvestron also knows what he is doing (I do not!) and is far more patient that I am. He finds another blown component: a 1N4740A Zener diode (something I had never heard of before).

Zener diode

I ordered both from Mouser Electronics, which I think is a US company (though my bits came from Hong Kong). Components were a couple of cents each (if you are in NZ – hit me up, I bought spares). Shipping was going to be $20 or sommin to New Zealand so I got sucked into Mouser’s free fast DHL delivery if you spend over $60.

Anyway, here are the parts:

The problem I ran into

I was a little heavy-handed removing the Zener diode and ripped hair-thin trace off top of board that connects across cathode of Zener. Dohhhhh! So: Be super careful removing the old diode!

Actually. Just be careful generally.

I managed to jerry rig a fix by splicing in some copper wire with Teflon tube (a trick I learnt on video below). The trace runs to an IC labelled ‘U3’ (could not read label on chip) and somewhere else (I soldered to broken trace and used some heat shrink tube to secure).

Anyway – it worked. Thanks, Silvestron.

Teflon wire trick (and loads of other stuff)