MC939 noisy speaker - GSM-Forum

doggyfreestart · 03-25-2004, 23:31

I can hear the GSM sending noises very loud in the speaker of my MC939. I tried another EEP dump but it didn't help. Any suggestion how to fix it?

Guest · 03-26-2004, 07:21

Change PMB2905.

Oxo_Boxo · 03-26-2004, 09:34

Quote:

Originally Posted by Guest

Change PMB2905.

...OR check two torx4 screw who fixed sim holder backpanel to pcb...

BR

kreitzz · 03-26-2004, 20:22

Quote:

Originally Posted by doggyfreestart

I can hear the GSM sending noises very loud in the speaker of my MC939. I tried another EEP dump but it didn't help. Any suggestion how to fix it?

Try first simple to rehot(resolder using hot air gun) PMB2905 radio &sound IC.

doggyfreestart · 03-31-2004, 20:46

Quote:

Originally Posted by kreitzz

Try first simple to rehot(resolder using hot air gun) PMB2905 radio &sound IC.

Okay, this worked perfectly, thanks. I rehot it and gave'em a little kick from the side when it was warm and now it is all OK.
But on another phone I face the following problem: charging isn't working correctly, it discharges the battery entirely (to 0V!) when I try to load. Which IC is faulty? Any suggestion?

kreitzz · 04-01-2004, 21:20

Quote:

Originally Posted by doggyfreestart

Okay, this worked perfectly, thanks. I rehot it and gave'em a little kick from the side when it was warm and now it is all OK.
But on another phone I face the following problem: charging isn't working correctly, it discharges the battery entirely (to 0V!) when I try to load. Which IC is faulty? Any suggestion?

Good work.
For disgarging repair you have to:
1) change sound amp - litle 8-pin TSOP IC below and left from battery connector. Attention: it has soldering pad on the bottom, so use only hot air gun, not soldering iron!
2) change charge controller - 6-pin IC - far right from the SIM connector, in names X4H or X4G.

Good luck!

doggyfreestart · 04-22-2004, 09:31

OK. So did I. Phone worked until I tried to charge it for the first time - since then when I switch it on the earth picture comes, and then phone keeps flashing as it does with desoldered EEPROM.
I have checked everything in the sound amps neighborhood, I swapped most of them as well, but the problem remains. I suppose I had a short circuit and it killed something - but what?

kreitzz · 04-22-2004, 12:20

Seems to be you had not only hw, but sw problem too. During repair operations you, may be, cause CPU or Flash damage (desoldering). Try to resolder them using hot air gun or BGA soldering station. If you'll flashing again, then rewrite eeprom IC.

Quote:

Originally Posted by doggyfreestart

OK. So did I. Phone worked until I tried to charge it for the first time - since then when I switch it on the earth picture comes, and then phone keeps flashing as it does with desoldered EEPROM.
I have checked everything in the sound amps neighborhood, I swapped most of them as well, but the problem remains. I suppose I had a short circuit and it killed something - but what?

doggyfreestart · 04-22-2004, 18:46

Hmmm.... I suppose BGA resoldering is a bad idea since all BGA ICs are glued. I hate it.
But I've swapped the EEPROM, phone is able to switch on now. I'm curious whether the replaced one is dead, and whether another charge attempt would kill the new one as well.
Besides, you deserve more than a bottle of beer for your attempts. If I can help you with anything please let me know. I really appreciate your help.

kreitzz · 04-22-2004, 19:48

You are welcome

Will be fine to test, if you don't have an shorten VCC to GND in EEPROM or sound amp neighbor.

Good luck, mate

Quote:

Originally Posted by doggyfreestart

Hmmm.... I suppose BGA resoldering is a bad idea since all BGA ICs are glued. I hate it.
But I've swapped the EEPROM, phone is able to switch on now. I'm curious whether the replaced one is dead, and whether another charge attempt would kill the new one as well.
Besides, you deserve more than a bottle of beer for your attempts. If I can help you with anything please let me know. I really appreciate your help.

03-25-2004, 23:31	#1 (permalink)
doggyfreestart Freak Poster Join Date: Apr 2002 Age: 46 Posts: 423 Member: 10679 Status: Offline Thanks Meter: 35	MC939 noisy speaker I can hear the GSM sending noises very loud in the speaker of my MC939. I tried another EEP dump but it didn't help. Any suggestion how to fix it?

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03-26-2004, 07:21	#2 (permalink)
Guest Insane Poster Join Date: Apr 2001 Location: KZ Age: 59 Posts: 89 Member: 4107 Status: Offline Thanks Meter: 1	Change PMB2905.

04-22-2004, 09:31	#7 (permalink)
doggyfreestart Freak Poster Join Date: Apr 2002 Age: 46 Posts: 423 Member: 10679 Status: Offline Thanks Meter: 35	OK. So did I. Phone worked until I tried to charge it for the first time - since then when I switch it on the earth picture comes, and then phone keeps flashing as it does with desoldered EEPROM. I have checked everything in the sound amps neighborhood, I swapped most of them as well, but the problem remains. I suppose I had a short circuit and it killed something - but what?

04-22-2004, 18:46	#9 (permalink)
doggyfreestart Freak Poster Join Date: Apr 2002 Age: 46 Posts: 423 Member: 10679 Status: Offline Thanks Meter: 35	Hmmm.... I suppose BGA resoldering is a bad idea since all BGA ICs are glued. I hate it. But I've swapped the EEPROM, phone is able to switch on now. I'm curious whether the replaced one is dead, and whether another charge attempt would kill the new one as well. Besides, you deserve more than a bottle of beer for your attempts. If I can help you with anything please let me know. I really appreciate your help.