Iphone 4 No Signal - GSM-Forum

beastien · 07-25-2012, 13:58

Is it normal for the centre pin on the GSM antenna to be shorted to ground?
If not, what could cause this problem?

beastien · 07-26-2012, 00:12

I've checked it against another working board, and there is about 1.4ohm to ground, so that isn't the problem.

Is there any suggestions for no signal/searching all the time? it's detecting the sim card correctly, the IMEI is there and it doesn't search when the sim card is out.

Also wifi is greyed out, could this be related?

air_chair256 · 07-26-2012, 06:46

hi
the antenna should be shorted to gnd
in manual searching its find any operator ? if its find the operator in manual searching change U1_RF if its not found any thing in manual search replacement U8_RF and U7_RF but be careful when you heat u1_RF or u8_RF maybe the baseband damaged and the iphone only show itunes cable and you must reball U9_RF and U8_RF

beastien · 07-27-2012, 03:54

Sorry, I forgot to mention that the board has had water damage. Could something have gone open circuit and lost voltage to the components. Is there any specific voltages I should look for around this area?

Also I have found the antenna connector on the board was damaged, and the outer part was most likely shorting to the centre pin.
I know the antenna looks like a short to ground normally, but could this have damaged anything?

07-25-2012, 13:58	#1 (permalink)
beastien Junior Member Join Date: Oct 2006 Posts: 18 Member: 362786 Status: Offline Thanks: 1 Thanked 0 Times in 0 Posts	Iphone 4 No Signal Is it normal for the centre pin on the GSM antenna to be shorted to ground? If not, what could cause this problem?

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07-26-2012, 00:12	#2 (permalink)
beastien Junior Member Join Date: Oct 2006 Posts: 18 Member: 362786 Status: Offline Thanks: 1 Thanked 0 Times in 0 Posts	I've checked it against another working board, and there is about 1.4ohm to ground, so that isn't the problem. Is there any suggestions for no signal/searching all the time? it's detecting the sim card correctly, the IMEI is there and it doesn't search when the sim card is out. Also wifi is greyed out, could this be related?

07-26-2012, 06:46	#3 (permalink)
air_chair256 Freak Poster Join Date: Oct 2011 Posts: 331 Member: 1679608 Status: Offline Thanks: 151 Thanked 189 Times in 109 Posts	hi the antenna should be shorted to gnd in manual searching its find any operator ? if its find the operator in manual searching change U1_RF if its not found any thing in manual search replacement U8_RF and U7_RF but be careful when you heat u1_RF or u8_RF maybe the baseband damaged and the iphone only show itunes cable and you must reball U9_RF and U8_RF

07-27-2012, 03:54	#4 (permalink)
beastien Junior Member Join Date: Oct 2006 Posts: 18 Member: 362786 Status: Offline Thanks: 1 Thanked 0 Times in 0 Posts	Sorry, I forgot to mention that the board has had water damage. Could something have gone open circuit and lost voltage to the components. Is there any specific voltages I should look for around this area? Also I have found the antenna connector on the board was damaged, and the outer part was most likely shorting to the centre pin. I know the antenna looks like a short to ground normally, but could this have damaged anything?