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820-00281 no sound - speaker amp IC cracked

A

ajdoc

Member
Client tried remove battery with installed logic board and he damaged U6550 (it is cracked).
No sound, no audio devices in system settings.
Removed that IC and found fried pad 23 but it has still connection with path.
Still no audio and not visible audio device in settings.

Will try with new IC but waiting for delivery.

Left fan is running on max rpm all the time.
Checked temp sensors in iStat menus and all looks OK (it is linked with speaker amp.

Is there any think what I can do before new speaker amp IC will arrive?

Thanks
 
2informaticos

2informaticos

Administrator
Staff member
The speaker amps connect directly with audio codec U6200; it may be damaged now.
Check resistors between PCH and audio codec.
Also check power rails of U6200.
 
A

ajdoc

Member
1.8V power rail going in U6200.
Resistors between PCH and audio codec R6203, R1310-13 are OK.

That speaker amp which was cracked had burned out pad. That line is AUD_SPKRAMP_INT_L and as you said it is connected directly with U6200. On that path there is R6291 which on one side it has PP1V8_S0 and resistance should be 47K but it is only 1.6K.

Checked rest of resistors around U6200 and here is what is not right:
R6227 should be 1.5K but it is 69Ohm
 
A

ajdoc

Member
AUD_I2C_1A_SCL - 0.053V
AUD_I2C_1B_SCL - 0.016V
AUD_I2C_1A_SDA - 0.330V
AUD_I2C_1B_SDA - 0.350V
 
2informaticos

2informaticos

Administrator
Staff member
Then the problem comes from U6300, or U6500/50.
Remove them (one by one) and check when AUD_I2C_1B_SCL goes high; in diode mode to ground.
 
A

ajdoc

Member
U6500 removed (U6550 was cracked at the start so it was removed at the begging) and AUD_I2C_1B_SCL got 0.340V in diode mode :)
Fitted R6229 back in place and audio device visible in settings and sound works on one channel :)
Waiting for delivery with speaker amp ICs.

Still left fan runs at max RPMs all the time - iStat temp sensors show all correct temps - any idea with that one?
 
A

ajdoc

Member
Diode mode between Q6000/50 areas are the same and resitors around Q6000/50 areas got the same resistance.
With new fan and new keyboard flex same issue.

edit: I just swapped logic board from another one and one fan is still on max rpms so all looks like some issue with keyboard/palmrest.
 
Last edited:
A

ajdoc

Member
Tried with good known trackpad and flex cable and same issue.
Swapped logic board to another machine and fan speed is working fine so on 99.9% keyboard/palmrest is faulty.
 
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