On Wed, 17 Feb 2016 14:39:49 -0000 (UTC), Cursitor Doom
wrote:

On Wed, 17 Feb 2016 08:48:08 -0500, legg wrote:

Your concern for this resistor's health is touching, but it really is
misplaced, as the part is easily replaced, relocated, temporarilly
beefed up or whatever.

Nice idea, but it's in series with the main transformer primary winding,
and I'd rather that resistor go up in smoke than the transformer. If I
replace it with a higher power one of the same value, it puts the primary
winding and other components at risk of fatal damage.

If you know what you want to do, in 15seconds, you can do a lot,
particularly if you're prepared to repeat the process at intervals,
until all the necessary info is accurately recorded.

It takes about 5 minutes to fully cool down and then give me another 15s
of probing. I could of course let it cool for just 90s, but then I'd
hardly have time to get a probe in place before it got too hot again. I
simply haven't the patience to work that way - and the fumes off that
resistor are not pleasant.



One thought has come to mind. Common advice on powering up a scope
after long terms out of service involves the use of a variac to
'reform electrolytics'. This advice may be counterproductive with some
switch-mode power supplies, which may never operate normally (for more
than ~20mS) at their low-line dropout voltage. It's just not something
that they are required to do, nor do they see this condition in normal
service. It's usually avoided by introducing considerable hysterisis
in the UVLO and start-up thresholds.

If you're confident that the high voltage bulk electrolytics are
functional, you should probably just apply normal mains input to the
fully loaded psu. This may allow it to function normally, if no stupid
substitutions or errors have been created by earlier meddlers.

Based on your response (or lack there of) to earlier suggestions, I
can only suggest now that you review previous posts on this subject.
I personally couldn't go farther in troubleshooting this unit without
running through those steps or gathering that information.

Best of luck anyways

RL