Samsung 214t locating bad caps on logic board using Fluke DMM

[budm]

I got this Samsung 214t that I re-capped (PANASONIC caps) the power supply/inverter board in 2009. The monitor comes on with lots of strange pattern on the screens. The caps still check out good, the 13V feeding the logic board is good at 13V. There are many regulators and buck converter power supply on board. The output of the regulators (they are not 1117 series) are within 2~3%.
There are many SMD Electrolytic caps on the board that will need to be checked. I do not have the scope with me so I set my FLUKE to frequency mode and start testing to see if I can see any frequency reading on the caps.
Two of the caps has about 52KHz reading, 1 has about 150Hz, two has variable frequency between 25~85Hz. All other caps show 0Hz.
I replace those 5 caps, check the frequency, and they are showing 0Hz, now I get good pictures on the screen. Gave the monitor back to the happy customer. I will wait and see if I will get to see this monitor so I can check the caps I put in and see how long they will last. I could have start by jumping the cap to see which one will bring back the pictures but using the meter to pin point which one is more fun. I use my Fluke in AC mode and Frequency mode a lot for locating AC ripple in the power supply circuits.

[retiredcaps]

Re: Samsung 214t locating bad caps on logic board using Fluke DMM

I use my Fluke in AC mode and Frequency mode a lot for locating AC ripple in the power supply circuits.

Good tip. I will have to try this for fun the next time I get a new project.

[budm]

Re: Samsung 214t locating bad caps on logic board using Fluke DMM

I really like this old Fluke 79III. Glad to see that you are still around, have not seen you posting much any more, cheers.

[dj_ricoh]

Re: Samsung 214t locating bad caps on logic board using Fluke DMM

I set my FLUKE to frequency mode and start testing to see if I can see any frequency reading on the caps.
Two of the caps has about 52KHz reading, 1 has about 150Hz, two has variable frequency between 25~85Hz. All other caps show 0Hz.
I replace those 5 caps, check the frequency, and they are showing 0Hz, now I get good pictures on the screen.

i know this sounds stupid but did you change those who show Hz more then 0? or the one who show actual 0

still learning

[budm]

Re: Samsung 214t locating bad caps on logic board using Fluke DMM

Good filter cap will show 0 Hz. The one that show any AC ripple are the ones that I replaced, 5 of them. Good filter cap will reduce the AC Ripple voltage to as small as possible. I will have to test my Fluke to see what is the smallest AC voltage and the Highest frequency it can detect.

[bluto]

Re: Samsung 214t locating bad caps on logic board using Fluke DMM

Oh noes! My precious 214T that I am staring at right now is going to have more bad caps... Thanks for the heads up!

[ohmmy]

Re: Samsung 214t locating bad caps on logic board using Fluke DMM

Great tip!

Two questions:

What's a good fluke meter to get if upgrading from just a cheapo brand

Would setting meter to ac volts and testing across a cap be a good indicator if it's bad or just using frequency mode?

[asdf123]

Re: Samsung 214t locating bad caps on logic board using Fluke DMM

Ok ! Now the Beginner asks!
Where did You measured the frequency!
Black to GND , and RED to CAP leg ?
Thanks!