21 May
2000
21 May
'00
9:47 a.m.
At 09:00 PM 5/20/00 +0100, Tony wrote:
You want to be careful doing this. You'll be alright doing it with linear
supplies, but switch-mode supplies are approximately constant _power_
devices and draw more current as the input voltage drops. Some burn out
in an expensive way if you run them off a reasonable fraction (but not
within the documented range) of the normal input voltage.
Hmmm, good point. I haven't done this with a switching PS but you're
probably right about what would happen.
Joe
> >If this terminal is really unused, it might be
worth going through and
> >swapping the electrolytic caps with some relatively new ones, but it
> >probably would work well otherwise. 20-year old electrolytics need to be
> >"re-formed" if they're to work reliably. That involves removing
them from
> >the circuit and gradually cycling them up to peak voltage and current. If
> >you have to remove them, it makes more sense to replace them rather
than
to
go through the re-forming process. Some of them may
die anyway, due to
tired dielectric.
I have a large Variac that I plug old stuff like this into and I use it
to gradually bring up to full voltage. I start at 10% for a few minnutes,
then go to 20% for 1/2 or so and then step it up another 20% every 1/2
hour. I've had no trouble with shorted caps since I started doing this.