I'm attempting to fix my desktop motherboard which is damaged by power surge, and I noticed that the +3.3VSB is giving 1.6 volts. There are few voltage regulators around the board, I checked them either and they're working correctly (Convert from 5v to 3.3v). I tried replacing the faulty one but it didn't solve the problem. Also there is 2 resistors and 1 capacitor connected to the regulator. The 2 resistors must be 316 and 182ohms, but they seems to be 118 and 113ohms. Can that be the problem? Why is there even 2 resistors connected to adjust pin when the voltage regulator is FIXED and doesn't need to be adjusted? :/

Btw I'm working with boardviewer app and I don't have a schematic. Thank you!

EDIT: The regulator is AMS1117-3.3v

  • 2
    \$\begingroup\$ We don't know what regulator it is so we can't know if the values are right. How about telling us the regulator type? Edit it to the question. Also, you can't measure the resistors while they are connected to the motherboard, so your measurements may be invalid. And the regulator may not be tje issue, there might be a broken component somewhere that pulls too much current and limits the regulator voltage. \$\endgroup\$
    – Justme
    Apr 24 '20 at 12:04
  • 1
    \$\begingroup\$ Remember that measurements of resistors still situated in-circuit may not be correct and there might be nothing wrong with them. \$\endgroup\$
    – StarCat
    Apr 24 '20 at 12:13
  • \$\begingroup\$ @Justme I edited the post. It's ams1117-3.3v . "there might be a broken component somewhere that pulls too much current and limits the regulator voltage." Well, I think that's probably the answer. Thank you mate. \$\endgroup\$ Apr 24 '20 at 12:33
  • \$\begingroup\$ @StarCat True. I didn't know that. :) \$\endgroup\$ Apr 24 '20 at 12:33
  • \$\begingroup\$ Without schematic it is very unlikely to help you solve the problem. In general, repair questions are out of scope at this Q&A-site. \$\endgroup\$
    – Ariser
    Apr 30 '20 at 6:37

The voltage regulator may not be fixed, you should check the actual number on the part of your board, otherwise it may be components placed so they could use either without having to worry about updating there tooling.

as for what is making it not work, I would check that adjust pin voltage against what is expected in the datasheet, normally its something like 1.2V, If this is less than 1.2V, is the part running hot? its possible there is an excessive load on the output that is causing it to go into a thermal protection mode

Other things you can do would be lifting the regulator and measuring to ground to try and spot a resistive short, beyond this, you would start looking at what is on that power rail, and if any components will allow you to subdivide it into smaller chunks to work out what part of it has gone wrong.

  • \$\begingroup\$ Adjust pin is having 1.07v. In the datasheet it says 1.25v. And yes the regulator gets hot. Sooo... There's probably a short somewhere. Right? \$\endgroup\$ Apr 24 '20 at 12:29
  • \$\begingroup\$ Very likely, that voltage difference is too large to be a tolerance issue. \$\endgroup\$
    – Reroute
    Apr 24 '20 at 12:40

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