Help needed with identifying a component  - Page 1
Forum section: electronics / repair

author: Lado
author_rank: Contributor
timestamp: October 23, 2023, 06:09:59 pm
content: I have a APC ES700 UPS that occasionally made a buzzing noise and sometimes the (no power) buzzer would go off. I took it apart and found a stuck relay. I tested it in circuit with a power supply and I blew a component. It has a hole in it. I can't find the replacement part and I need help identifying it.Pictures:https://ibb.co/gFMT6HChttps://ibb.co/FzJ8Vdchttps://ibb.co/BN0td34

author: fzabkar
author_rank: Super Contributor
timestamp: October 23, 2023, 06:48:00 pm
content: Could we see the part in the context of its surroundings?http://markingcodes.com/search/c/A%3FW

author: Lado
author_rank: Contributor
timestamp: October 24, 2023, 07:01:37 am
content: What exactly? The markings of the other components on this PCB or where it connects to, the main PCB?

author: fzabkar
author_rank: Super Contributor
timestamp: October 24, 2023, 04:56:23 pm
content: Show us a photo of the whole PCB.We would be looking for markings such as Qnn (transistor) or Unn (IC). The locations of capacitors would help us to determine the Vcc and ground pins, or Vin and Vout in the case of an LDO regulator. You could help us by locating these power pins yourself.A PCB designer will often choose several parts from the one manufacturer, so identifying the manufacturer of other parts might help to identify the damaged one.Otherwise, feel free to search for your part among 41 pages of results.

author: Lado
author_rank: Contributor
timestamp: October 25, 2023, 05:27:16 pm
content: I understand. I hoped it was simpler than that since only one character was missing.I think I found the same model of UPS so I'll try to open it and find the markings of the damaged component.That would definitely help identifying the component, right? It would be the easiest solution. I hope it's not like on some components where they mark the batch instead of the component number.One more question, since my knowledge is pretty basic. What did I do wrong to blow the component? It's a 12 V relay and I gave it 12V and 0.1 or 0.5 A. Can't remember. Could the wrong polarity be the issue?

author: fzabkar
author_rank: Super Contributor
timestamp: October 25, 2023, 05:37:08 pm
content: Sorry, I just had another look at your photos. I missed it the first time, but is the damaged part the one with a circuit reference of D20? If so, then that is a diode. If this diode is connected across the relay coil, then it is a snubber, in which case reverse polarity would certainly kill it.The "W32" part is a PDTC143XT NPN resistor-equipped transistor by Nexperia:https://assets.nexperia.com/documents/data-sheet/PDTC143X_SER.pdf(datasheet)https://ae01.alicdn.com/kf/Sc61e5d686652477996866e278dc25205k/10PCS-100-New-PDTC143XT-W32-T32-SOT23-3-Chipset.jpg(photo)The marking style of the diode is similar, so I expect it is also a Nexperia diode. This diode would only need to be a standard silicon rectifer, probably 100V, 1A or less.A BAW56 dual diode (marking A1W) could fit the bill.<-- No, this a common anode pair.https://www.aliexpress.com/w/wholesale-baw56.html(photos)https://www.mouser.com/datasheet/2/916/BAW56-3081460.pdf(datasheet)

author: amyk
author_rank: Super Contributor
timestamp: October 26, 2023, 04:29:27 am
content: Didn't even have to look at pictures, just read description and thought "almost certainly a freewheel diode". In general, it's a very bad idea to apply power to components in-circuit without understanding where that power will go.I hope the diode was the only thing you killed.

author: Lado
author_rank: Contributor
timestamp: October 26, 2023, 05:10:29 am
content: Yeah, I wanted to take it out but I forgot about it once I took the PCB out.I tested the relay on the main board too, but nothing smoked there so I hope it will work 😔That one I didn't take out because I could barely get to it and I was afraid that taking everything apart would cause more harm.The shematic I found stated that the burned component labeled D20 was a dios 1N4148.All the links showed a regular diode so I thought the information was wrong.The good news is that I found a working UPS and took it apart to fined the markings of a burned component.Here's the comparison with my unit:https://ibb.co/Mc13Z4mhttps://ibb.co/mvyMdRV

author: fzabkar
author_rank: Super Contributor
timestamp: October 26, 2023, 05:57:55 am
content: BAV70 double diode, 100V, 215mA per diode, common cathode:http://markingcodes.com/search/c/a4whttps://assets.nexperia.com/documents/data-sheet/BAV70_SER.pdf

author: Lado
author_rank: Contributor
timestamp: October 26, 2023, 09:07:28 am
content: I already ordered this:BAV70 A4 0.2A 70V Switching Diode SOT-23 SMD SOT Transistorhttps://a.aliexpress.com/_mO7CdDQHopefully everything will work.Thank you everyone for helping!I'll report once the parts arrived.

author: Lado
author_rank: Contributor
timestamp: November 16, 2023, 05:55:34 pm
content: Update:When tested in circuit, the relay wouldn't switch every time. I ordered a new one and replaced it, along with the burned diode.It didn't repair the device, it made it worse 💀😂The old relay worked fine when I took it out.Then I remembered that I've found a video saying it's a capacitor fault. I didn't test them because I don't have an ESR meter, just the capacitance mode on my multimeter. The capacitors were hard to get, hard to unsolder due to the bent legs so I gave up after testing the first one. I didn't want to damage the PCB by burning it or lifting traces.After replacing the relay, I had nothing to lose.My local electronics store didn't have the right capacitors. They gave me 60V instead of 25V. I know there's some leeway in voltage but I wasn't sure if that wasn't too much. I replaced almost all the capacitors since they were under $2 all together and now the device works!It's funny that a 4.7 uf capacitor can mess up the whole device and make it buzz, although there's no visual signs that the component is bad.Thanks everyone for helping!

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 16, 2023, 08:55:56 pm
content: At least you have a local electronics store. How nice!!Higher voltage rated caps are almost never a problem as long as they are the same type of cap. Different types of caps can be a problem.