18 Jan
2009
18 Jan
'09
11:09 a.m.
On 18 Jan 2009 at 18:35, Gordon JC Pearce MM3YEQ wrote:
I repair a lot of synthesizers, some of which have
truly horrible linear
power supplies which are terribly undercooled. Lots of people bang on
about how the capacitors only last 15 years and become dried out from
the heat and need replaced. Well, I've changed one electrolytic cap,
dozens of rectifiers (bridges and diodes), and resoldered hundreds of
dry joints. Caps are the last thing I look at. Plus, if a power supply
cap is on the way out, you'll get audible hum which is a dead giveaway.
Most of the electrolytic problems I've seen associated with age have
been with the ones inside of sealed "wall warts" where the heat from
the transformer eventually cooks the juices out of them. Short of
cracking open a fused-together housing, the only viable alternative
is to replace the whole thing.
How I hate those things! No standard on the connectors--a wart
putting out 20vac will often have the same plug as one putting out
3vdc, they often don't have the same brand on them as the device
they're powering, take up 2 or more slots on a power strip and can't
be reliably operated from a power strip mounted under a table top,
lousy wire leads and hidden fuses. The nadir of 20th century
technological innovation...
Cheers,
Chuck