1
\$\begingroup\$

I recently open up brother's APC sine wave UPS to fix and trying to repair some damage that usually happen over time due to age by replacing components I suspect one by one.

When I start doing AC output LC filter, I notice the UPS triggering surge light on surge protectors connected to UPS output again and again but only when switch to battery operation.

Currently, UPS have 6 AC output in parallel and 3 surge protectors from vendor A, B and C hooking to them and 3 directly to other device.

Vendor A very well known in U.S. and B and C only midgrade from Costco.

Previously, before I start fix, only surge protector from vendor A trip some time, but now all surge protector trip the moment I cut UPS input power making it switch to battery operation!

I not be explain this besides that some change I did is making output sine wave peak perhaps swing above (1.7 * 120)V AC?

But I only change component with expensive high quality parts and as per original datasheet spec, so UPS is actually better than new (but brother not willing to believe as he sees opposite and he paid for all expensive high quality parts himself after I request him with confidence).

Old circuit pics still visible: Old circuit pics

\$\endgroup\$
  • 1
    \$\begingroup\$ Exactly what components have you replaced? What was wrong with the UPS beforehand? What tools do you have available? (e.g. Oscilloscope, Multimeter, ...) \$\endgroup\$ – Oli Glaser Aug 2 '12 at 5:57
  • \$\begingroup\$ @OliGlaser: Capacitors, resistors, MOVs; exactly by part number. Original noise problem I describe in link 'Old circuit pics' \$\endgroup\$ – sekharan Aug 2 '12 at 5:59
  • \$\begingroup\$ I read the other post - was the UPS actually faulty or was it just making a buzzing noise? Why have you replaced all these components? \$\endgroup\$ – Oli Glaser Aug 2 '12 at 6:02
  • 1
    \$\begingroup\$ Without being able to see what's gong on with a scope it will be very difficult to troubleshoot something like this. Also without a schematic/service manual things will be difficult. Sorry to sound discouraging, but if you do not have prior experience fixing power supplies it would probably be better take it to someone who does for repairs. If you are absolutely committed though, we will try our best to guide you, but you will have to provide as much information as possible (diagram of setup, relevant waveforms, UPS model number/datasheet, pictures etc). \$\endgroup\$ – Oli Glaser Aug 3 '12 at 3:23
  • 1
    \$\begingroup\$ No, it's not normal. It could be a faulty surge protector, but it's more likely to be the UPS if you have been working on it. To find out more, measure the voltage and current with a multimeter, and check with a scope. \$\endgroup\$ – Oli Glaser Aug 12 '12 at 0:11
1
\$\begingroup\$

One thing to always do if something doesn't work as well as it did before you started to work on it: LOOK CAREFULLY at everything you did. There may be a solder trace short or a pinched wire or a missing screw.

| improve this answer | |
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.