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.