Author Topic: Weird Problem with ISDN Telephone (ELMEG CS 410)  (Read 203 times)

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Offline MagnumGR

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Weird Problem with ISDN Telephone (ELMEG CS 410)
« on: March 26, 2020, 02:08:51 pm »
Hi

I have an ISDN telephone, the ELMEG CS 410 (S0) which my last months have the following problem:
It is attached to my ISDN PBX, when on the phone, i detach - attach the telephone cord (S0) or when the  PBX restart for reason like power failure etc., the phone is DEAD it's not power up !

If i connect the telephone (ELMEG) to another telephone line (S0), it's also dead .
If i connect another ISDN telephone to the telephone cord (S0), it working normally !

If i leave the specific device several days (over 10 days) disconnected from the line S0, when i reconnect to it (S0) it power up and it works !!

Over the past two months, however, without any interrupt (power failure etc) the phone suddenly, it's act like taking reboot but then it's power off with the same symptom as above.


So I opened it and saw the board:

[attach=1]


At first glance I looked for bad capacitors but optical all is in good shape.

I want to try to change the capacitors, but i 'm not sure for the exact type because it's SMD capacitors.
Is the following correct  ?
Pieces >Marking >  Type 
1x>      3V 470 6.3V   -> 470mF 6.3V (?)
5x>      m3 10 16V     -> 10mF 16V  (?)
1x>      45 1 100V      -> 1mF 100V (?) 
1x>      431 22 50Z   -> ?
1x>      422 100 6E ->   ?

Any other suggestion to look for ?
 

Online shakalnokturn

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Re: Weird Problem with ISDN Telephone (ELMEG CS 410)
« Reply #1 on: March 28, 2020, 10:02:58 am »
Good idea for the SMD electrolytics, you have the values right if you meant μF rather than the mF you wrote.
Leave the tantalums alone.

I'd definitely check the solders at the white transformer between the buzzer and RJ45 sockets, they look bad on your picture as far as I can tell.
 
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Offline MagnumGR

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Re: Weird Problem with ISDN Telephone (ELMEG CS 410)
« Reply #2 on: March 29, 2020, 08:53:30 am »
Thanks for your reply !

Tantalums is the last 2  capacitors that i don't understood what type is ?

 

Online Twoflower

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Re: Weird Problem with ISDN Telephone (ELMEG CS 410)
« Reply #3 on: March 29, 2020, 09:55:04 am »
Check the ferrite on the left center (close to the elmeg lettering). It looks like the placement was off quite a bit. On the picture it looks like that at least one of the pads (Pin 8) is discolored (caused by bridging the pin-pad gap by sparks?).

OK, shakalnokturn saw it first, and I haven't read all replies...
« Last Edit: March 29, 2020, 09:58:33 am by Twoflower »
 
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