find replacement for inductor  - Page 1
Forum section: electronics / beginners

author: insomnia
author_rank: Newbie
timestamp: September 20, 2023, 04:37:36 pm
content: Hello,I have a broken raspberry 4. The mxl7704 is broken and also 1 inductor. I can buy the mxl7704 for arround 4 euro on Aliexpress. But the inductor is giving me options with 20 euro shipping and that is to much. Can i replace this inductor with a simular smd component or a through hole component or any other options?I allready found the power circuit and it is the L1 line which provides the 3.3V. According to this it should be a 4u7 1.7A. Is that the same as a 0.47uH ?https://datasheets.raspberrypi.com/rpi4/raspberry-pi-4-reduced-schematics.pdfIt is simular like this topic but here the L3 is broken. They say it is a Bourns SRN2512-R47M - Fixed Inductor 470 nH 4.4A 32 MOHM. I need the one for the L1 linehttps://raspberrypi.stackexchange.com/questions/103610/rpi4b-power-connector-smd-components-damaged-how-to-replace-it

author: wraper
author_rank: Unknown
timestamp: September 20, 2023, 04:46:47 pm
content: Quote from: insomnia on September 20, 2023, 04:37:36 pmNo, 4u7 is 4.7uH. As of mxl7704, you need particularly MXL7704-P4

author: wraper
author_rank: Unknown
timestamp: September 20, 2023, 04:58:40 pm
content: BTW did you verify if MXL7704 is actually bad? If inductor is broken, it could be the only issue. Also the most common failure I've seen is mechanically damaged FPF1320 (bare silicon die) IC which switches SD card voltage.

author: BillyO
author_rank: Super Contributor
timestamp: September 20, 2023, 10:56:59 pm
content: Any inductor of the correct inductance and the same or higher power rating will do. It might not look nice, but it will do.

author: insomnia
author_rank: Newbie
timestamp: September 21, 2023, 07:58:07 am
content: you're right i have a mxl7704-p4. I took off the bad inductor (it had a hole in it) and looked with my thermal camera. The mxl7704 is getting very hot. I will take a look at the fpf1320. How can i measure it?

author: wraper
author_rank: Unknown
timestamp: September 21, 2023, 08:30:43 am
content: Quote from: insomnia on September 21, 2023, 07:58:07 amFirst it's visual inspection if it's not cracked. Even nicked corner may kill it. Second it should output 3.3V when run with no micro SD card, when running with SD card it should drop to 1.8V after a short moment. However it may not also if CPU is bad. You can measure it across capacitor circled red on the photo. On newer revision boards IC is placed on opposite side of the board and this capacitor is turned 90 degrees.As of verifying if MXL7704 is the problem (if some of output voltages aren't right), you can measure resistance to GND on 4 power rails before, and if there are shorts, after desoldering it. Resistance on 1V1 rail should be 10 to 100+ Ohm depending on RAM type on the board, Samsung resulting in lowest. VDD_core should be like 25-200 Ohm. The rest in kOhm range. If short(s) remain after desoldering MXL7704, most likely CPU is bad.

author: insomnia
author_rank: Newbie
timestamp: September 24, 2023, 09:41:06 pm
content: Hello, i measured both boardsL1 1,68Kohm and 1,52KohmL2 62Kohm and 40KohmL3 67ohm and 10ohmL4 55ohm and 43ohmSo looks like both MXl are dead