I have a little problem repairing my LCD power supply (22 inch old monitor). I already change the damaged capacitors (one is good but i change all 5 anyway, last image bottom right). The problem didn't solved then i continue searching why don't turn on the monitor.

Now i find a component that appears to be bad, it looks like a diode, but the symbol is for inductor if my memory dont fail.

It's completely black, and i cant figure what is it. I tested and is in short circuit without any resistance.


Somebody know what is it?

Anyway the PSU is this one: YP1504PG 6871TPT318G 207.01.03 REV 1.3

I checked the voltage in the output and must be 2x 5v and 2x 15v but no one give current. Anyway the monitor dont start, but the filter fills and remains with about 340V (the two at bottom left). psu

Thankyou in advance

  • 3
    \$\begingroup\$ Looks like a ferrite bead inductor (commonly used for interference suppression) so 0 ohms is correct. The PCB tells you it's an inductor anyway. \$\endgroup\$ Nov 16, 2016 at 10:03
  • \$\begingroup\$ Kind of interesting how that component is the most asked here. Like no one knows what ferrite beads are. Anyways, the components susceptible to heat are the one that are likely to get damaged. You just have to try out yourself. \$\endgroup\$
    – Bradman175
    Nov 16, 2016 at 10:34

1 Answer 1


It looks like the supply is not running. This could be due to a defective IGBT or Mosfet.(Q101?). This kind of failure is not uncommon in monitor and tv sets.

I do not know if you had a blow fuse. If that has been the case than you need to replace the rectifier. (The flat in the left bottom corner). The main capacitors (68uF 450V) Select new ones with 630V. Q101 also. Most probably a component with a voltage limit of 450 V. Replace that with an equivalent but now 630V.

A rectifier could get damaged in case of a short circuit. Remeber you can only test for errors not for upcomming errors.

Replacing parts with higher voltage increases the error margin and forms a better protection against spikes.

Once you are there it could be that the system is running and hopefully not more is defective.

the bead inductor should be ok. Even if shorted out the inverter should run

  • \$\begingroup\$ Hello and thanks for the help. The fuse is right. The 240v current flow until the 450v capacitors. Anyway i tested the rectifier and dont give me any lecture. I go to remove from the board and test again. Why is better to change theh capacitors to 630V? same uF? \$\endgroup\$
    – VicHaunter
    Nov 16, 2016 at 12:11
  • \$\begingroup\$ After testing the rectifier appears to be fine. I read in one direction and with 2000k scale it shows 1700 in each part. \$\endgroup\$
    – VicHaunter
    Nov 16, 2016 at 12:25
  • \$\begingroup\$ Concerncing the rectifier is not a lecture. If the rectifier has been exposed to a short circuit it could be damaged. Dont forget that you can only test what is wrong. Not what is good. See my updated answer. \$\endgroup\$
    – Decapod
    Nov 16, 2016 at 16:08
  • \$\begingroup\$ Thanks for the help, finally the rectifier shows 560 in only one direction in diod mode. Then i understand that is ok. I'm pending to find a capacitors tester to see the filter ones if are ok. Any other sugestion? \$\endgroup\$
    – VicHaunter
    Nov 17, 2016 at 7:41

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