Burned component in power supply  - Page 1
Forum section: electronics / repair

author: decoder_82
author_rank: Regular Contributor
timestamp: July 26, 2023, 05:03:58 am
content: Hello !I am restoring a power supply when opening it, I noticed a component with signs of overheating. See picture.Looking at the schematics it appears to be D609. It is an ERC25-06 rectifier.The component tests good. Also the adjacent resistor. The power supply provides correct output voltage.Should I replace it ? I am wondering if this was caused by failure of another component?

author: wasedadoc
author_rank: Super Contributor
timestamp: July 26, 2023, 07:22:25 am
content: Looks to me that over a long time the heat from the pink resistor has charred the sheath to its right.

author: decoder_82
author_rank: Regular Contributor
timestamp: July 26, 2023, 07:28:50 am
content: Thanks so if there resistor tests within range you would leave it like this ?

author: coromonadalix
author_rank: Super Contributor
timestamp: July 26, 2023, 09:46:25 am
content: i would create more space between the resistors by slightly bend them appart, the brownish color is caused by heatthe capacitor under the jacket is fine ...unless the psu need recapping i would only create some space ...

author: decoder_82
author_rank: Regular Contributor
timestamp: July 26, 2023, 07:42:04 pm
content: Thanks yes good idea I will do that.All caps have good ESR values and no sign of leak so I am hesitant to replace them.

author: tooki
author_rank: Super Contributor
timestamp: July 26, 2023, 11:49:36 pm
content: What I would do is check the solder side of the board for any damage to the solder joints. You can see that the board itself has gotten rather toasty, and if that heat was cyclic (i.e. it cycles between hot and cold), that can damage the joints. Just reflow the joint with a bit of fresh solder if necessary.

author: decoder_82
author_rank: Regular Contributor
timestamp: July 27, 2023, 03:04:23 pm
content: Indeed some solder joints were in bad shape. Surprising that the power supply is working. Will reflow them.

author: elecdonia
author_rank: Frequent Contributor
timestamp: July 27, 2023, 05:08:00 pm
content: It would be useful to review the schematic for this power supply. Do you have a schematic which can be posted?I wonder why that one particular resistor runs so hot?It is good that all capacitors on the PC board still have in-spec ESR.Reflowing solder connections on single-sided PC boards like this one is a great way to increase the reliability and life-expectancy of the power supply.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: July 28, 2023, 10:26:03 pm
content: If the PS works, I would consider putting a new resistor of higher wattage rating (bigger component) in and have it sit higher from the board. It appears you have room for that. That will help dissipating the heatSometimes some components do run quite hot even if the rest of the components on the board are OK.I just fixed a NEG 48 vols Switching PS. One resistor was OPEN with some evidence of heating of the board. Failed resistor was only slightly discolored. There are two identical PS in the chassis and the working one has the failed component running quite hot also. This is an "uninterruptible" PS. I believe that the failed one was the one mostly used and the working one was the "backup".I do not like SMPS but need to get over my aversion because they are so common. Perhaps someone could suggest a self help group?

author: Fusion916
author_rank: Regular Contributor
timestamp: July 28, 2023, 11:24:09 pm
content: Quote from: Wallace Gasiewicz on July 28, 2023, 10:26:03 pmThis made me laugh a little.