*BANG!* Done it again!

[John Robertson]

On 2017/05/08 1:33 PM, Ralph Mowery wrote:

In article <g6udnWVlCZwnXY3EnZ2dnUU7-SudnZ2d@giganews.com>,
jmelson@wustl.edu says...

John Robertson wrote:

On 2017/05/07 5:31 AM, Cursitor Doom wrote:
On Sun, 07 May 2017 10:19:45 +0000, Cursitor Doom wrote:


But I can't see any sign of anything nearby having burned up. <shrug


You were dialing the unit up in an effort to reform the electrolytic
capacitors, and if you didn't know that before now you do (look up the
term).
The problem is, this may be catastrophically wrong with modern gear with
swtiching power supplies. Old tube gear could very often be brought back to
like like this. But, switching supplies are constant power devices, and if
they start up at exceedingly low voltage, they will draw excessive current.
So, one may have to reform capacitors out of circuit on such gear.

Jon

It is often a bad idea to bring electronics up slow. Switching supplies
do not like it. Some of the older tube equipment does not do well
either unless most of the tubes are removed. You can run into what is
called cathode stripping.

If the capacitors need the reforming, many times they will not last very
long after. The equipment may seem to work ok, but it will often not be
at its best.

Good points about equipment not liking slow power up. I will remember
that in case the question comes up again.

We don't bother with reforming caps at our shop, we run an ESR test, if
the cap passes, great, if it fails, we replace it. Not worth the call
backs otherwise.

Thanks,

John