T28 Network Problem - GSM-Forum

unoche · 12-22-2002, 22:26

Hi evryone ,
I have a lot of T28 ,T20, T29, A2618 that after ''power on'' show the operator's name but the no signal bar is present on the display. If i make a call the phone shows ''network problem'' and sometimes after a few minutes the display shows NO ACCESS.

I have changed PA and antenna switch but the defect still remains , i also tried to rework the phone's solders with hot air .Does anybody Know what the problem is?

Thanks

mightym · 12-22-2002, 23:40

You have bad RF signal procesor !!! Change it and all will be OK !
Thats all

unoche · 12-23-2002, 14:29

Hi mightym !

Can you tell me where rf processor is located on pcb board or the signature marked on it ?

Thank you for your reply!

.::AkhavanGSM::. · 12-23-2002, 17:01

dear mate.
the RF processor is the same thing that you may know as PA.
try to change it.
the problem will be removed if you replace it well
Good louck.LIGHt

GSM Coolhawk · 12-23-2002, 17:30

@unoche

The RF Signal processor is called "N234" The PA is called "N400". You'll see this numbers from the service manaul, find the board layout and you'll see the placement. The RF Processor as I remember (correct me if I'm wrong) it, is also called IF Module?

Also try to reflow the MMCC "Multi Mode Converter Circuit", it's located just under the CPU called "N800". But please be aware if you chnage this chip, you'll need to recalibrate Radio, Voltage and current of the phone, so better leave it on. This chip also causes "No power on" sometimes

The RF Processor is the big square IC with visible legs, no solder "under the chip", and it'll take a steady hand to change it, better first try to reflow it with good flux, have seen quite some T28 with this chip badly soldered.

(Note: This chip is the FIRST chip I check if I have a T28 "no signal". In 60% of the cases this is the one faulty in my exsperince)

@GSMLight
I must strongly disagree with you that the PA=RF Signal Proceesor.

Regards

pali · 12-23-2002, 17:50

I have same problem .
I have several r320, t28 ... with NO NETWORK,
I changed RF signal proc. but still no network. Do i need to reflash phone or what? What temperature is suitable for RF signal proces not to kill it ?

b.r.

Pali

mightym · 12-24-2002, 00:28

PA = RF >>> Wrong 1000%
unoche you have wery good ehplanation posted by GSM Coolhawk.

pali · 12-24-2002, 13:54

???
I know that PA is not RF sig. proc..
I'm just asking what should be problem.
I changed on R320 with no network and still no network.
I changed for new one.
Which temperature is good for it ?
Do i need flash after change?
b.r.

Pali

mightym · 12-25-2002, 23:48

For pali !!!
Maby your problem is not in RF sig.proc. try contiue with swither and at the end change PA. !!! MUST WORK !!!
Send results
P.S. RF is first thing in most cases that should be changed but not always
mightym

pali · 12-26-2002, 08:27

@mightym

Do u know how for sure can i check if it is or not RF sig proc ?
i think 300C will kill RF sig. proc or not ? So what temperature is ok for changing RF sig. procesor ?
Is antena switch compactible with any other , for example from any nokia ?
thanx for reply.

b.r.

Pali

Keke · 12-26-2002, 09:59

The way I see but never try yet the nokia 6210 ant switch should be compactible

mightym · 12-26-2002, 11:19

Yes it compatibile !!! I change it all ok but with litle less signal streinght,but It have one more problem paralel with switch About temperature I work with 327-335 C and nothing happend to me, all works never kill anything !!!
But for SIEMENS CPU be extra carefull never heat IC in the midle you will brake it in the sec.also sagem IC-s NOKIA,ERICSSON, PHILIPS,ect ect no problem on that temperature
All the best mightym

Chuk · 12-26-2002, 13:07

It's may be RF Tranciever 3004.... as I remember.

Safety temperatures:

270-280 C for high air flow rate
230-250 C for slow air flow rate

mightym · 12-26-2002, 19:11

Yea maby that temperature, but proces is quite longer !!!
mightym

pali · 12-30-2002, 10:00

Problem remains. i changed 3 new RF signal procesors but not helped..
any other idea?

b.r.

Pali

12-22-2002, 22:26	#1 (permalink)
unoche Junior Member Join Date: Oct 2002 Location: Italy Age: 42 Posts: 13 Member: 16704 Status: Offline Thanks: 0 Thanked 1 Time in 1 Post	T28 Network Problem Hi evryone , I have a lot of T28 ,T20, T29, A2618 that after ''power on'' show the operator's name but the no signal bar is present on the display. If i make a call the phone shows ''network problem'' and sometimes after a few minutes the display shows NO ACCESS. I have changed PA and antenna switch but the defect still remains , i also tried to rework the phone's solders with hot air .Does anybody Know what the problem is? Thanks

12-23-2002, 14:29	#3 (permalink)
unoche Junior Member Join Date: Oct 2002 Location: Italy Age: 42 Posts: 13 Member: 16704 Status: Offline Thanks: 0 Thanked 1 Time in 1 Post	info Hi mightym ! Can you tell me where rf processor is located on pcb board or the signature marked on it ? Thank you for your reply!

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12-22-2002, 23:40	#2 (permalink)
mightym Freak Poster Join Date: Dec 2002 Location: Serbia Age: 37 Posts: 150 Member: 18812 Status: Offline Thanks: 6 Thanked 1 Time in 1 Post	You have bad RF signal procesor !!! Change it and all will be OK ! Thats all

12-23-2002, 17:01	#4 (permalink)
.::AkhavanGSM::. No Life Poster Join Date: Jun 2002 Location: Iran Age: 37 Posts: 1,086 Member: 12724 Status: Offline Thanks: 1 Thanked 30 Times in 23 Posts	dear mate. the RF processor is the same thing that you may know as PA. try to change it. the problem will be removed if you replace it well Good louck.LIGHt

12-23-2002, 17:30	#5 (permalink)
GSM Coolhawk No Life Poster Join Date: Dec 2001 Location: United Arab Emirates, Dubai Age: 41 Posts: 1,279 Member: 7751 Status: Offline Thanks: 2 Thanked 72 Times in 20 Posts	@unoche The RF Signal processor is called "N234" The PA is called "N400". You'll see this numbers from the service manaul, find the board layout and you'll see the placement. The RF Processor as I remember (correct me if I'm wrong) it, is also called IF Module? Also try to reflow the MMCC "Multi Mode Converter Circuit", it's located just under the CPU called "N800". But please be aware if you chnage this chip, you'll need to recalibrate Radio, Voltage and current of the phone, so better leave it on. This chip also causes "No power on" sometimes The RF Processor is the big square IC with visible legs, no solder "under the chip", and it'll take a steady hand to change it, better first try to reflow it with good flux, have seen quite some T28 with this chip badly soldered. (Note: This chip is the FIRST chip I check if I have a T28 "no signal". In 60% of the cases this is the one faulty in my exsperince) @GSMLight I must strongly disagree with you that the PA=RF Signal Proceesor. Regards

12-23-2002, 17:50	#6 (permalink)
pali No Life Poster Join Date: Nov 2001 Location: Slovakia Posts: 1,001 Member: 7586 Status: Offline Thanks: 1 Thanked 10 Times in 9 Posts	I have same problem . I have several r320, t28 ... with NO NETWORK, I changed RF signal proc. but still no network. Do i need to reflash phone or what? What temperature is suitable for RF signal proces not to kill it ? b.r. Pali

12-24-2002, 00:28	#7 (permalink)
mightym Freak Poster Join Date: Dec 2002 Location: Serbia Age: 37 Posts: 150 Member: 18812 Status: Offline Thanks: 6 Thanked 1 Time in 1 Post	PA = RF >>> Wrong 1000% unoche you have wery good ehplanation posted by GSM Coolhawk.

12-24-2002, 13:54	#8 (permalink)
pali No Life Poster Join Date: Nov 2001 Location: Slovakia Posts: 1,001 Member: 7586 Status: Offline Thanks: 1 Thanked 10 Times in 9 Posts	??? I know that PA is not RF sig. proc.. I'm just asking what should be problem. I changed on R320 with no network and still no network. I changed for new one. Which temperature is good for it ? Do i need flash after change? b.r. Pali

12-25-2002, 23:48	#9 (permalink)
mightym Freak Poster Join Date: Dec 2002 Location: Serbia Age: 37 Posts: 150 Member: 18812 Status: Offline Thanks: 6 Thanked 1 Time in 1 Post	For pali !!! Maby your problem is not in RF sig.proc. try contiue with swither and at the end change PA. !!! MUST WORK !!! Send results P.S. RF is first thing in most cases that should be changed but not always mightym

12-26-2002, 08:27	#10 (permalink)
pali No Life Poster Join Date: Nov 2001 Location: Slovakia Posts: 1,001 Member: 7586 Status: Offline Thanks: 1 Thanked 10 Times in 9 Posts	@mightym Do u know how for sure can i check if it is or not RF sig proc ? i think 300C will kill RF sig. proc or not ? So what temperature is ok for changing RF sig. procesor ? Is antena switch compactible with any other , for example from any nokia ? thanx for reply. b.r. Pali

12-26-2002, 09:59	#11 (permalink)
Keke No Life Poster Join Date: Jun 2002 Location: CT SA Age: 41 Posts: 1,385 Member: 12733 Status: Offline Thanks: 5 Thanked 21 Times in 19 Posts	The way I see but never try yet the nokia 6210 ant switch should be compactible

12-26-2002, 11:19	#12 (permalink)
mightym Freak Poster Join Date: Dec 2002 Location: Serbia Age: 37 Posts: 150 Member: 18812 Status: Offline Thanks: 6 Thanked 1 Time in 1 Post	Yes it compatibile !!! I change it all ok but with litle less signal streinght,but It have one more problem paralel with switch About temperature I work with 327-335 C and nothing happend to me, all works never kill anything !!! But for SIEMENS CPU be extra carefull never heat IC in the midle you will brake it in the sec.also sagem IC-s NOKIA,ERICSSON, PHILIPS,ect ect no problem on that temperature All the best mightym

12-26-2002, 13:07	#13 (permalink)
Chuk No Life Poster Join Date: Dec 2001 Location: Ukraine Age: 35 Posts: 1,150 Member: 7767 Status: Offline Thanks: 0 Thanked 3 Times in 3 Posts	It's may be RF Tranciever 3004.... as I remember. Safety temperatures: 270-280 C for high air flow rate 230-250 C for slow air flow rate

12-26-2002, 19:11	#14 (permalink)
mightym Freak Poster Join Date: Dec 2002 Location: Serbia Age: 37 Posts: 150 Member: 18812 Status: Offline Thanks: 6 Thanked 1 Time in 1 Post	Yea maby that temperature, but proces is quite longer !!! mightym

12-30-2002, 10:00	#15 (permalink)
pali No Life Poster Join Date: Nov 2001 Location: Slovakia Posts: 1,001 Member: 7586 Status: Offline Thanks: 1 Thanked 10 Times in 9 Posts	Problem remains. i changed 3 new RF signal procesors but not helped.. any other idea? b.r. Pali