rescued a beehive!

From: Joe <rigdonj_at_intellistar.net>
Date: Sun May 21 09:47:03 2000

At 09:00 PM 5/20/00 +0100, Tony wrote:
>> >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.
>
>
>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
Received on Sun May 21 2000 - 09:47:03 BST