On Aug 13, 10:25 am, Robert Redelmeier wrote:
This applies when diagnostics are easy and cheap. As they might
be for you or me. The undersized neutral is easy to check with
a DVOM: just measure AC from neutral to ground. Anything more
than a volt or two means trouble. Much easier than disturbing
connections (which usually makes problems disappear).

All three numbers on each wall receptacle (neutral to ground,
neutral to hot, ground to hot) also report informative facts. Many
will not obtain those numbers because the numbers mean nothing to
them. They forget. Numbers are major facts and create useful replies
from the other side of usenet.

Provided were numerous simple and inexpensive diagnostics. For
example a 50 foot three wire extension cord test. An icon on the
desktop that runs a script to collect ping and other useful numbers.
The $10 line filter. But a $500 UPS only to perform diagnostic
testing? A $500 UPS does not eliminate all possible electrical
problems - as was assumed. So if the problem still exists, does that
prove it is not from AC mains? No. Circuits still exist to carry AC
electric anomalies completely around that UPS.

A UPS that outputs a sine wave does not define a double conversion
UPS. That model (if I have properly recognized it) is simply a
standby supply with a cleaner output. It still connects router
directly to AC mains when not in battery backup mode; does no
electricity 'cleaning'. That UPS also would not provide useful
information on the OP's router lockup.

A better test. Buy a cheapest UPS. Run router from that UPS in
battery backup mode. Does that 'dirty' electricity cause router
lockup? If not, then is router lockup due to AC electricity? Another
diagnostic that is so much less expensive.