Help identify component in ac/ac halogen lamp power supply - Page 1
Forum section: electronics / repair

author: manosmat
author_rank: Newbie
timestamp: March 08, 2025, 10:49:33 am
content: Hi all, can you help me identify the marked component in pic1? its in an ac power supply for halogen roof lamp, in series with a cbb 0.22mf 400v cap. Next to those components a same cbb cap (C2) was burned and removed. In pic2 and pic3 an exact same power supply from an other lamp is displayed in which you can see the unidentified component (black casing with marking c-600v on it and nothing else). Is it my idea or this also needs replacement?Thank you in advance,M

author: club
author_rank: Newbie
timestamp: March 08, 2025, 01:08:06 pm
content: Hi Manosmat, IMHO the dead element is a simple power resistor, inserted into an insulating PVC tube; it seems to me that it was connected in series with C1. If you have another same but working PSU, you can measure the resistance value in the working one.Sorry, I have no idea why only "C1" is shown on the PCB, nor why c-600v was printed on the PVC plastic tube. Perhaps it is a design mod that uses the pre-mod PCB.However, I fear that the resistor has been damaged due to excess thermal dissipation, and the cause should be found first. There could have been unwanted contact with a foreign body. The capacitor C1 may be leaking (or short-circuited). The PSU switching frequency has increased significantly (you should find out why).Good luck

author: reodor
author_rank: Contributor
timestamp: March 08, 2025, 01:42:06 pm
content: Since it is wrapped in plastic, could it be a fusible resistor? They are common in switched mode power supplies. They dampen the inrush current surge, while also acting as a fuse.

author: Gyro
author_rank: Super Contributor
timestamp: March 08, 2025, 01:57:48 pm
content: If it's a series RC network then it is a snubber to control edge rate or ringing. It is most likely a manufacturing mod, maybe to pass EMC certification or to reduce a semiconductor excessive failure rate.

author: Swake
author_rank: Frequent Contributor
timestamp: March 09, 2025, 07:58:46 am
content: Same as@reodorThe matt pink paint of that component + the sleeve around it heavily points towards a fusible resistor.Remove it on the good board and post a picture please. We'll decipher the color code marking as it might be a little tricky compared to a normal resistor.The probability that it is an inductor is low, it would also have a glossy paint.

author: Gyro
author_rank: Super Contributor
timestamp: March 09, 2025, 10:21:34 am
content: @manosmat:Slightly OT, but this might be a good time to consider replacing these Halogen roof lights (interior ceiling downlights?) with modern spec (must be fire rated) LED downlights. Not only will you save a lot of electricity but ceiling/roof space fires can be particularly nasty. Something caused that resistor to fail in that way - comparing with the other one that shows no signs of overheating.Just a thought.

author: manosmat
author_rank: Newbie
timestamp: March 16, 2025, 04:16:46 pm
content: Thank you very much, yes, its probably a snubber RC, I ll try to remove the working part, measure and post pics.