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Old 20th January 2009, 05:44 AM   #1
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Default Help me please, problem with my ALEPH 5

Hello everybody,

For some time I have a problem with my 5 ALEPH
(PCB DESIGN).
The right channel, works with a stifled and distorted sound.
I placed a protective kit speaker
against the DC current that goes into default.
Can someone guide me in my troubleshooting?

Best regards.

Thierry BASSAL.
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Old 20th January 2009, 11:58 PM   #2
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Hi

Last night i made some tests (see original N PASS Schématic)

OFFSET : 35,2 V

Tension between MOSFET Source Résistor

R41 : 0,61 V
R41 : 0,58 V
R42 : 0,60 V
R66 : 0,58 V
R65 : 0,58 V
R64 : 0,58 V

It must be ok

Tension between INPUT MOSFET Résistor

R11 : 4,83 V it must be ok
R14 : 8,40 V (it seems high ?)

Dont you feel there is a problem with Q1 ?

Regards

Thierry
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Old 21st January 2009, 12:45 AM   #3
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Just to be safe, I'd re-match and install a new pair Q1, Q2. According to Aleph 5 schema, you should have 4-5 volts across R14.


-john
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Old 24th January 2009, 01:07 PM   #4
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Looks like Q2 is probably open or bad solder joint. As John said, replace Q1 and Q2 with a new matched pair unless you find a fault in your wiring-soldering.
Bill
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Old 25th January 2009, 03:28 PM   #5
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Hello,

According to pass lab design,

I replaced Q1 - Q 2 - Q 3 with new matched IRF9610.

New tests :

V - : - 39 V
V+ : + 39 V

R11 : 4,78 V
R14 : 5,10 V
R40 : 0,61 V
R41 : 0,59 V
R42 : 0,61 V
R64 : 0,60 V
R65 : 0,58 V
R66 : 0,58 V
Z5 : 8,68 V

OFFSET : 100 mV

The sound is always distorded and stifled.

I am lost ...

Thierry.
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Old 25th January 2009, 05:46 PM   #6
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All your measurements look OK. If one channel works compare more component measurements between channels. Check the components values, look for bad solder joints, look for wiring mistakes, check your pinouts on semiconductors.
Bill
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Old 26th January 2009, 07:24 PM   #7
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I know it may be trivial; but have you tried swapping the inputs from your source and/or preamp?
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