Please help me identify these Unknown Components - Page 1
Forum section: electronics / repair

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: May 26, 2022, 02:12:26 pm
content: Hello!I have a small circuit board that I think is a PFC board, but I'm not sure.It's a smaller board, on a 48v LiFEPO4 battery charger.The unknown components are marked as UK1, UK2 and UK3I realize I may have to desolder them to test them better, but I was wondering if they could be identified without doing so.Here are the measured characteristics and a photo......UK1Resistance Test: 2.18K ohms with VOM leads connected either wayCapacitance Test: No reading regardless of VOM lead connectionsDiode Test: Beep and 0.728v when positive lead on Left, 1.6v when Positive lead connected on Right side with no VOM beep.Continuity Test: No continuity regardless of which way the leads are connectedUK2Resistance Test: 6.93M ohms with VOM Positive Lead connected to the bottom, Negative lead to the top terminal, 5.17M when the leads are reversedCapacitance Test: No reading regardless of VOM lead connectionsDiode Test: Beep and 0.643v when positive lead on top terminal, 1.988v when Positive lead connected to bottom terminal with no VOM beep.Continuity Test: No continuity regardless of which way the leads are connectedUK3Resistance Test: 0.740K ohms with VOM leads connected either wayCapacitance Test: .0L reading regardless of VOM lead connectionsDiode Test: VOM Beep and 0.803v when positive lead on top terminal, 0.807v when Positive lead connected to bottom with VOM beep.Continuity Test: No continuity regardless of which way the leads are connected - 0L

author: fzabkar
author_rank: Super Contributor
timestamp: May 27, 2022, 02:32:04 am
content: Whenever I see a white smd component, I expect it to be a precision component. I've seen quite a few precision resistors, but no capacitors. However the following article suggests that your mystery component may indeed be a precision capacitor.https://www.elprocus.com/what-is-a-smd-capacitor-types-its-applications/Quote

author: strawberry
author_rank: Super Contributor
timestamp: May 27, 2022, 07:12:04 am
content: definitely not precision for product that cost 10$ , lucky getting 5% parts0.47..1nF capacitors for TL494 timing and feedback compensationsometime they solder some resistors upside down (to cut price?) but seems not in this case

author: gamalot
author_rank: Super Contributor
timestamp: May 27, 2022, 07:49:51 am
content: They look like common ceramic capacitors to me.

author: picburner
author_rank: Frequent Contributor
timestamp: May 27, 2022, 03:11:46 pm
content: I found only one other pcb on the net called "XLS3.PCB" and it is also a different revision.However in the latter UK1 and UK2 would appear to be capacitors while UK3 would appear to be a resistor.This pcb, from what I could understand, should be part of a 60V lithium battery charger.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: May 27, 2022, 11:01:42 pm
content: Quote from: strawberry on May 27, 2022, 07:12:04 amThat would seem to make sense, but oddly, I have two of these and on one of these boards they used a LM358 and on the other an OPA1612 (which is a prohibitively expensive OpAmp for such a low cost device?Well, if you buy these chargers they cost about $60 I believe.

author: MathWizard
author_rank: Super Contributor
timestamp: May 28, 2022, 12:26:54 am
content: Have you mapped out the circuit ? That would help a lot too, to guess what they are

author: strawberry
author_rank: Super Contributor
timestamp: May 28, 2022, 05:56:07 am
content: Quote from: ThermallyFrigid on May 27, 2022, 11:01:42 pmcould be the same LM358 to get into 10$

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: May 29, 2022, 01:58:39 am
content: Quote from: MathWizard on May 28, 2022, 12:26:54 amI'm mapping out some of it in an attempt to do just that.Thanks

author: fzabkar
author_rank: Super Contributor
timestamp: May 29, 2022, 02:03:37 am
content: Quote from: strawberry on May 27, 2022, 07:12:04 amI consider NPO capacitors to be precision types (if that's what they are), but maybe others would not.

author: strawberry
author_rank: Super Contributor
timestamp: May 29, 2022, 05:17:12 am
content: NPO (C0G) better tempco and less microphoniccan get precision between +/-1pF...20%https://eu.mouser.com/ProductDetail/YAGEO/CC0805KRNPO9BN102?qs=57cj7OiSijl0sOrTylTGAQ%3D%3D

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 29, 2022, 06:51:30 pm
content: I'd say they're 100pf or so.1nf+ are usually slightly darker, but doesn't always apply.