Hoefer PS 500 Power Supply

Wolfgang Schechinger novalidaddress at nurfuerspam.de
Wed May 3 17:05:35 EST 2006


I think, it's a thermal drift, probably due to a defective part or a
bad soldering point.
I you have access to an electricial workshop (you're at ...edu, aren't
you? - there should be one), it would be the easiest to ask them for
assistance: If they are not just trained (?!?) in exchanging complete
circuit boards at random and/or sending equipment back to the
manufacturer, they should know what to do.

If not and you know some basics about electronics, connect a suitable
load (eg a lightbulb and voltage and ampere meters if not present in
the supply) and check the individual parts with cold spray (from your
favourite local electronic shop): When you hit the damaged one, the
voltage or the current should immediately change. Then: happy
soldering!

If you can dissect the schematic by eyeballing, first, I'd look in the
power stage, then in the sensing and control section. If it's a
switching power supply (to be recognized by the ABSENCE of a huge
transformer but by the presence of several smaller transformers and
coils (and usually chirping noise when you operate it), you need to be
extremely cautious as the unit will use rectified mains voltage (up to
400 volts DC, depending on your local mains voltage) which may kill you
by heart failure if you touch the 'hot' leads by accident. Put (at
least) one hand in your pocket!

HTH

Wolfgang Schechinger
Endocrine Research Lab
University Hospital "Bergmannsheil"
Bochum, Germany

PS please reply to the group, the email address above ends in autotrash



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