Need help deciphering inductor label on laptop schematic to find replacement. - Page 1
Forum section: electronics / repair

author: JeffBloomgold
author_rank: Newbie
timestamp: June 23, 2024, 01:31:21 pm
content: Hello!I'm attempting to repair a fault in a Dell Inspiron 5770 motherboard which prevents the battery from charging or the laptop from running off of battery. I've found a very obviously blown inductor and found a schematic to see what I need to get to replace it with. However I have a few questions on how to decipher its label in the schematic (see attached image of the battery circuit schematic - it's PL4 in that image.)It's labeled as "5A Z150 20M 1210_2P"5A is 5 amps and I assume it's the rated current but didn't know if it might be the current saturation.Z150 is something I have no idea about. I found one seller of SMD inductors that has this Z150 as part of its model number/marking and assume that's probably all it is, but was hoping to get some clarification.20M: Not sure if this is 20% tolerance or if it's an inductance value of 2.0uH? If it's the latter, what is the M for. If it's the former, what is the inductance value?1210: type of case2P: No idea what this meansAlso after a bit more reading, it looks like Z150 might be in reference to impedance and 20M in reference to frequency? Is there some way to tell what kind of replacement I need to get if so?Thanks all!

author: fzabkar
author_rank: Super Contributor
timestamp: June 23, 2024, 03:05:12 pm
content: QuoteI don't see it.

author: JeffBloomgold
author_rank: Newbie
timestamp: June 23, 2024, 05:26:56 pm
content: Hmmm looks like I goofed and forgot to attach it. Here it is. I also attached an pic of the motherboard/inductor itself.Edit: Also, is this actually a ferrite bead?

author: helius
author_rank: Super Contributor
timestamp: June 23, 2024, 05:42:59 pm
content: 2P means it is a "2 pin" device with two terminals. Many EMI suppressing "inductors" are actually chokes with 4 pins.Ferrite beads are one kind of inductor. The other type is made of wire wound around a bobbin inside a piece of iron or ferrite.5 A current is quite high for a 1210 case device, it may be difficult to match that.Look at the Würth Elektronik 742792312: 1210 case, 0.03 ohms at DC, 110 ohms at 1000 MHz, 65 ohms at 100 MHz. 3000 mA DC current.

author: JeffBloomgold
author_rank: Newbie
timestamp: June 23, 2024, 05:55:10 pm
content: I also found this one Helius:https://www.mouser.com/ProductDetail/Fair-Rite/2512061217Y5?qs=paL1wOLBYNdLzI%2FVPVZ0Rg%3D%3DPackage / Case: 1206 (3216 metric)Impedance: 120 OhmsMaximum DC Current: 5 ATolerance: 25 %Maximum DC Resistance: 20 mOhmsI figure the size of the case is close enough to work but I wasn't sure how close to the original values I need to get in order for it to work well. I'm a bit of a newb if you couldn't tell

author: wasedadoc
author_rank: Super Contributor
timestamp: June 23, 2024, 06:04:00 pm
content: Inductors are rarely the prime cause of failure. Very likely that some other failure has caused excessive current to flow though it. Unless you remedy that the replacement inductor will suffer the same fate as the original.

author: fzabkar
author_rank: Super Contributor
timestamp: June 23, 2024, 06:05:53 pm
content: Here's an idea. Why don't you just upload the entire schematic? Your excerpt shows 3 ferrite beads (PL1,2,3) but not PL4. Your arrow is pointing to PL2.PL4 appears to be involved in a switchmode supply, or at least the adjacent MOSFET would seem to suggest that.

author: JeffBloomgold
author_rank: Newbie
timestamp: June 23, 2024, 06:18:27 pm
content: Yup that's my bad. Looks like I searched using "5A Z150 20M 1210_2P" rather than PL4. I didn't realize I could upload pdfs on here but attached is a screenshot of the schematic in the right spot, as well as the rest of the schematic.

author: wasedadoc
author_rank: Super Contributor
timestamp: June 23, 2024, 06:23:36 pm
content: If PL4 is the only fault you can temporarily replace with a short circuit and the battery will charge.

author: fzabkar
author_rank: Super Contributor
timestamp: June 23, 2024, 06:30:11 pm
content: That's clearer now, thanks. PL4 is indeed an EMI filter, and PQB03 appears to be functioning as a load switch.

author: fzabkar
author_rank: Super Contributor
timestamp: June 23, 2024, 06:40:36 pm
content: Quote from: JeffBloomgold on June 23, 2024, 01:31:21 pmhttps://www.analog.com/en/resources/analog-dialogue/articles/ferrite-beads-demystified.html

author: cruff
author_rank: Regular Contributor
timestamp: June 23, 2024, 06:44:08 pm
content: Have you checked all of the chip capacitors attached to the battery input line for shorts?

author: JeffBloomgold
author_rank: Newbie
timestamp: June 23, 2024, 07:53:34 pm
content: Not yet no, but I plan to do that before I hook it back up to power.Thanks everyone for your help!!! The plan now when I get a bit more time is to check to see if any of the capacitors are shorted and if not, short the pads from the burned out ferrite bead and see if that restores function - then worry about finding a suitable replacement.

author: JeffBloomgold
author_rank: Newbie
timestamp: June 23, 2024, 10:52:30 pm
content: Ok so none of the capacitors are shorted but would I be correct that 3 of them seem to be missing?? At least when comparing the boardview with the actual motherboard? Or am I missing something basic?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 24, 2024, 03:04:16 am
content: They probably mean 5A rating, 150 ohms impedance at 20MHz, 1210 chip size, multilayer ferrite chip bead.It's an odd choice as a bead that size (fairly high impedance at lowish frequency) is likely saturated under most any kind of load (100s mA).Hard to say how well it was designed/chosen, or added out of superstition without actually validating its effect.Missing components appear to be DNP ("Do Not Place"). The solder joints look reflowed as-is, nothing broken off. Often, a board is fully soldered (solder paste spread everywhere it might possibly be needed) and component placement is left off as needed. Presumably they simply didn't need every capacitor in those locations.Tim

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 24, 2024, 04:59:21 am
content: Who characterize at 20MHz anyway?20 milliOhms sounds more likely, and actually achievable within the context of other parameters.Bourns MH3225-151Y

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 24, 2024, 08:17:57 am
content: Resistance, that too.Char freq. varies with type, there are "low frequency" and "high frequency" parts that might be measured at 20MHz or even lower, or at 1GHz for example.Tim

author: JeffBloomgold
author_rank: Newbie
timestamp: June 24, 2024, 09:51:16 am
content: @ArdWarYes, I only realized that after further reading after I said that.That was based off of some answer to a similar question I found on an EE stack exchange.@ T3sl4co1lAhhh thank you that explains so much about the "missing" components. I'm still very much a beginner so there's still a lot of things I don't know that I don't know about. I think at this point, since none of the capacitors in that circuit are shorted, I'm just going to remove the blown component and jump the pads with a bit of wire or solder and see how that does.Edit: It did the trick! Battery is charging now and the laptop runs on battery alone now. I'm just going to let it run for awhile and see if it does anything suspicious.