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gtwibell
Topic Author
Posts: 7
Joined: Fri Nov 03, 2006 11:56 pm
Location: UK

Yet Another PSU Repair...

Wed Jul 25, 2012 3:57 am

I must have done well to get this far without a PSU failure, but inevitably it has finally happened. Failure of C906 is to blame, dropping the 9.5volt rail to around 4volts. I found an excellent circuit diagram and PCB layout here http://jfhelectronics.webs.com/soundbridgepowersupply.htm which will help enormously as I embark on a fix.

Rather than go the external route I intend to repair (or replace) the original internal PSU. Have a few ideas about extending its life and so far plan to do the following:

    Replace all the electrolytics with low ESR, 10,000 or 8,000 hour equivalents, rated at a higher voltage than the originals (so 50V instead of 35V etc).
    Dispense with the afterthought shielding box and instead use self adhesive copper foil to line the entire rear housing, leaving the PSU board open.
    Possibly enlarge the two heatsinks and/or contrive to conduct their heat through the housing to the outside, or maybe into the copper foil.
    In extremis (and with a clear impact on the bass performance) make a hole in the central recess in the base of the rear housing and fit a miniature fan externally. This will suck outwards with the bass port acting as the air inlet.

Will update on progress.
 
DieHardR1000
Posts: 2
Joined: Tue Jul 24, 2012 10:27 pm

Re: Yet Another PSU Repair...

Thu Jul 26, 2012 1:43 pm

I'd really be interested in the part numbers and manufacturers that you choose. Can you post them once you have your solution dialled?

I'm not electronics wiz but can handle a soldering iron pretty well. So an internal fix is within my ability if I can borrow your plan.

Thks
S.

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