iphone4 broken M/B at the edge - No display - Page 1
Forum section: electronics / repair

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 05, 2019, 05:22:05 pm
content: The M/B broke at the left edge, the phone is powering up, but no display at all. I have sounds and is connecting normally with USB with full access to the data files.The missing (broken) part is a gold piece of metal that is directly connected to a white 6 pin IC (the IC is still on the main M/B). What's the role of this IC that is receiving some kind of feedback info from this gold metal pin? Can I bypass it someway?

author: ataradov
author_rank: Super Contributor
timestamp: June 05, 2019, 05:35:34 pm
content: 6 pin component is a balun, not an IC, the part that broke off is an antenna. It should not affect operation of the device.So there is something else wrong with it. Probably some traces on the middle layers broke as well. I'm not sure how easy it would be to fix.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 05, 2019, 07:07:37 pm
content: Quote from: ataradov on June 05, 2019, 05:35:34 pmThanx Alex,Its the main antenna of the phone?

author: ataradov
author_rank: Super Contributor
timestamp: June 05, 2019, 07:54:59 pm
content: I don't know about iPhones, I just know how an antenna and a balun look like. So I have no idea what antenna it is.But the failure is not due to antenna, there is no way to detect that it is actually missing. Something else broke as well.

author: Johnny10
author_rank: Frequent Contributor
timestamp: June 05, 2019, 08:18:11 pm
content: You can fire these things up out of the case.Connect the display connector and make sure connector is fully seated, that's most of problems.I am more familiar with iphone 5s.http://asc.kh.ua/files/iphone-4-schematic.pdfBroken part is for GPS antenna

author: wraper
author_rank: Unknown
timestamp: June 05, 2019, 08:34:47 pm
content: Did you try attaching different display? If there was impact that was able to damage PCB, I would assume that LDC was likely damaged as well. Also is backlight working or not?

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 06, 2019, 07:28:00 am
content: Quote from: Johnny10 on June 05, 2019, 08:18:11 pmthanks for the schematic. The problem at the beginning was only the on/off button. After that, the M/B was broke at this specific point at the closing procedure.The phone starts but no backlight or LCD is working now.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 06, 2019, 07:29:16 am
content: Quote from: wraper on June 05, 2019, 08:34:47 pmNo, I don't have a spare display. The PCB broke at the closing procedure after pressure on it. The backlight is not working as well.

author: wraper
author_rank: Unknown
timestamp: June 06, 2019, 11:36:26 am
content: Quote from: sdancer75 on June 06, 2019, 07:29:16 amYou mean when you were putting LCD into enclosure? If so, I guess both of them got damaged. Try shining light onto LCD, there might be an image actually with only backlight lacking.

author: montarbo
author_rank: Contributor
timestamp: June 06, 2019, 01:07:22 pm
content: First check the FL3 and FL4, these small ferrits usually goes bad. If any one is open then try to bridge and see if u get LCD backlight.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 06, 2019, 03:54:30 pm
content: Quote from: wraper on June 06, 2019, 11:36:26 amThe LCD was never touched. I took out only the M/B without touching the LCD. I tried to replace the on/off button, while the LCD cables were just in the back of this switch (I am saying that because I am not sure if they damaged). Then I re-installed the M/B with a little pressure (that's how I broke the antenna) and I re-connected all the cables.Without closing the back I tried to power up the phone. The back of the M/B gets hot and the beep sound -a sign of a USB connection- is repeated again and again. However, I have access to my files using iFunBox.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 06, 2019, 03:57:05 pm
content: Quote from: montarbo on June 06, 2019, 01:07:22 pmContinuity test?

author: wraper
author_rank: Unknown
timestamp: June 06, 2019, 03:59:06 pm
content: Quote from: sdancer75 on June 06, 2019, 03:54:30 pmI forgot it's iphone 4, since 5 you need to remove display first.

author: Johnny10
author_rank: Frequent Contributor
timestamp: June 06, 2019, 05:41:41 pm
content: Whenever my iphone 5S gets hot it is because it is searching for a signal in an area with little coverage.In other words it is doing a lot of something. Searching, churning.Do you have microscope or magnifier to check over your motherboard?I bent a connector on a phone the other day and it heated up quite quickly when I turned it on.Have you backed up your phone?Might be a good idea before it stops working altogether.

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 06, 2019, 07:02:22 pm
content: Quote from: Johnny10 on June 06, 2019, 05:41:41 pmMine it gets hot maybe because I broke the antenna and it tries to find a signal? I don't know, the SIM card is out of the system.Yes, I have a microscope but I doubt if I can see any visible damages. I have also to desolder the front metallic panels that cover the CPU and the Memory.Since I still have access to the file system, yes I got everything I needed and just for curiosity, I am thinking to buy a used iphone4 just to help me find the root of this problem.... Maybe I will learn something about iphones.

author: Johnny10
author_rank: Frequent Contributor
timestamp: June 06, 2019, 07:53:10 pm
content: I bought 10 Iphones a couple of years back, when they were still worth 300 dollars, a hot air station and various tools.My problem was I couldn't supply a fully functional phone after repairing them because of fingerprint sensor.All but 5 phones had the home button ribbon cable destroyed from improper opening of case.I sold some, kept some, what did I learn?Do the repair for someone who is going to pay you for your time. :-)I had fun though.And yikes, those resistors and caps are small !

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 07, 2019, 08:04:49 am
content: Quote from: Johnny10 on June 06, 2019, 07:53:10 pmIt seems also that the ribbon cable has been damaged in my case. Check the photo attached.Yes, I absolutely agree about the time, but this is not for paying job but rather a learn and emotional motivation.So, have the non-apple original display replacement parts the same quality? Are they worth to buy them? For example, the "Sinbeda AAAA Screen For iPhone 4s 4" is advertised as a triple-A quality. What do you say?https://www.aliexpress.com/item/32921229335.html?spm=2114.search0604.3.2.6f787029PX13xW&ws_ab_test=searchweb0_0%2Csearchweb201602_2_10065_10068_319_10059_10884_317_10887_10696_321_322_10084_453_10083_454_10103_10618_10304_10307_10820_10821_537_10302_536%2Csearchweb201603_53%2CppcSwitch_0&algo_expid=c4396389-625f-4a37-9ef3-b7ba3f3273ec-0&algo_pvid=c4396389-625f-4a37-9ef3-b7ba3f3273ec&transAbTest=ae803_5

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 07, 2019, 08:09:42 am
content: Quote from: montarbo on June 06, 2019, 01:07:22 pmAccording to the schematic, theFL3andFL4are beside theJ4_APconnector, but all I can see are small SMD capacitors.

author: Rasz
author_rank: Super Contributor
timestamp: June 07, 2019, 08:46:16 am
content: weird, I see signal filters on your picture

author: montarbo
author_rank: Contributor
timestamp: June 07, 2019, 09:27:30 am
content: According to the schematic, theFL3andFL4are beside theJ4_APconnector, but all I can see are small SMD capacitors.See attached pic, encircled, continuity test.

author: JackJones
author_rank: Regular Contributor
timestamp: June 07, 2019, 09:33:26 am
content: Inductors can look a lot like capacitors, but notice how the colour of the body is different. The inductors are much darker than the capacitors.

author: montarbo
author_rank: Contributor
timestamp: June 07, 2019, 10:03:48 am
content: Since screen PFC damaged then replace it, almost all screens from china are the same. The one you linked to or cheaper version, don't Think u'll notice much of a difference.

author: Johnny10
author_rank: Frequent Contributor
timestamp: June 07, 2019, 11:55:02 am
content: As for replacement LCD screens, I found screens which I think are easily equal to original for 5s from a wholesaler that Louis Rossman used. Can't remember their name.However in US you can buy a 4s excellent condition for between 20 and 45 dollars, why keep fighting?You have broken motherboard, questionable cables, no GPS.I bought an iPhone 5s 16GB this week brand new for 90 shipped to me.It came a few days ago and is an excellent phone.Being on this forum, I know knowledge is more important than time !

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 07, 2019, 01:39:38 pm
content: Quote from: montarbo on June 07, 2019, 09:27:30 amSee attached pic, encircled, continuity test.They seem to me like capacitors :-)Thanx

author: sdancer75
author_rank: Frequent Contributor
timestamp: June 07, 2019, 01:41:53 pm
content: Quote from: Johnny10 on June 07, 2019, 11:55:02 amTo learn something from that. I don't care about the phone, I already bought other.

author: Johnny10
author_rank: Frequent Contributor
timestamp: June 07, 2019, 02:19:03 pm
content: Completely understand... I repair Oscilloscopes, DMMs, Function generators, Cap testers, power supplies, just for my own understanding.Enjoy the journey!