Leaky Crowbar SCR?
On 19/08/2017 17:06, Jon Elson via cctalk wrote:
On 08/19/2017 03:17 AM, Dominique Carlier via cctalk wrote:
Hello Marc,
In fact no, i am not really sure, I checked twice all the
big filtering caps but as you with a low voltage tester.
These caps comes apparently from a new old stock and some
doubts persists now.
I admit, I don't know how to test these caps at rated
voltage with my tools or in situ with the caps inside the
working (and thus closed/packed/connected) PSUs
It could also be an open rectifier diode. The caps might
store enough charge to keep the regulator from dropping out
at light load, but the DC input sags under more load. You
could check for AC on the DC output when it starts to fail.
It could also be a fuse socket that has developed some
resistance, although when that gets bad, the heat causes the
fuse to fail. We had a Versatec printer that this would
happen to every 5 years or so. The fix was to clean the fuse
clip with the finest sandpaper available and put in a new
fuse (even if you caught it before the fuse blew.)
Jon
--
Wanted one pdp-8/i rocker switch leaver to copy.