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Go Back   GSM-Forum > GSM & CDMA Phones / Tablets Software & Hardware Area > Sony Ericsson > Sony Ericsson Hardware Repair

Sony Ericsson Hardware Repair Post here your Hardware Repairing Hints or Problems with SonyEricsson and Sony Phones.

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Old 12-22-2002, 23:26   #1 (permalink)
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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
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Old 12-23-2002, 00:40   #2 (permalink)
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You have bad RF signal procesor !!! Change it and all will be OK !
Thats all
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Old 12-23-2002, 15:29   #3 (permalink)
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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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Old 12-23-2002, 18:01   #4 (permalink)
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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
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Old 12-23-2002, 18:30   #5 (permalink)
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@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
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Old 12-23-2002, 18:50   #6 (permalink)
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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
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Old 12-24-2002, 01:28   #7 (permalink)
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PA = RF >>> Wrong 1000%
unoche you have wery good ehplanation posted by GSM Coolhawk.
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Old 12-24-2002, 14:54   #8 (permalink)
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???
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
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Old 12-26-2002, 00:48   #9 (permalink)
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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
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Old 12-26-2002, 09:27   #10 (permalink)
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@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
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Old 12-26-2002, 10:59   #11 (permalink)
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The way I see but never try yet the nokia 6210 ant switch should be compactible
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Old 12-26-2002, 12:19   #12 (permalink)
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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
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Old 12-26-2002, 14:07   #13 (permalink)
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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
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Old 12-26-2002, 20:11   #14 (permalink)
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Yea maby that temperature, but proces is quite longer !!!
mightym
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Old 12-30-2002, 11:00   #15 (permalink)
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Problem remains. i changed 3 new RF signal procesors but not helped..
any other idea?

b.r.

Pali
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