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Old 25th November 2010, 03:00 PM   #1
kp93300 is offline kp93300  Malaysia
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Default Completed aleph J --loud cracking sound on switch off

Hi All,
I need help to solve the problem.
I just completed the aleph J and noted a very loud cracking sound through the loudspeaker on switch off of the power supply.
It is very quiet on switch on and no hum at all.
The dc offset at output is less than 0.2 V but swing to about 1 to2 V on powering down.
I am using a CLC type of line filtering with about 200000UF caps. The L is wound on a EI transformer , diy type.
I also use about 11 uF of motor start non polar caps at the last stop.
Could this be the problem ?

appreciate all the help

kp93300
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Old 25th November 2010, 03:07 PM   #2
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Default Cracking sound

Hi kp9etc,
Sounds very much like arcing inside the power switch. Suggest you put snubbers/switch click suppressors across each section of the switch, consisting 0.1F "Y" type capacitor in series with 100-120R resistor, or buy them ready made from RS or farnell.

John
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Old 25th November 2010, 03:24 PM   #3
Zen Mod is offline Zen Mod  Serbia
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you can check John's idea with simple test - instead of using mains switch to power off amp - just plug power cord from wall .
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Old 25th November 2010, 04:16 PM   #4
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Default Cracking

Good idea Wilson, didn't think about that one, Capt. Mainwaring

John
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Old 25th November 2010, 09:23 PM   #5
kp93300 is offline kp93300  Malaysia
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Quote:
Originally Posted by Zen Mod View Post
you can check John's idea with simple test - instead of using mains switch to power off amp - just plug power cord from wall .
To power off, I pull the power cord from the ac receptacle and the problem persisted.
kp93300
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Old 25th November 2010, 09:31 PM   #6
Zen Mod is offline Zen Mod  Serbia
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pictures , please
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Old 25th November 2010, 09:32 PM   #7
kp93300 is offline kp93300  Malaysia
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Quote:
Originally Posted by John Caswell View Post
Hi kp9etc,
Sounds very much like arcing inside the power switch. Suggest you put snubbers/switch click suppressors across each section of the switch, consisting 0.1F "Y" type capacitor in series with 100-120R resistor, or buy them ready made from RS or farnell.

John
Will a 1/2 w resistor be ok ?
Can I use x2 rated ? Is the value of 0.1uF critical ? Smaller and larger value ?

thanks
kp93300
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Old 25th November 2010, 09:46 PM   #8
Zen Mod is offline Zen Mod  Serbia
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considering this :

Quote:
Originally Posted by kp93300 View Post
To power off, I pull the power cord from the ac receptacle and the problem persisted.
kp93300

this will not help :


Quote:
Originally Posted by kp93300 View Post
Will a 1/2 w resistor be ok ?
Can I use x2 rated ? Is the value of 0.1uF critical ? Smaller and larger value ?

thanks
kp93300
problem is somewhere else , not in power switch
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Old 27th November 2010, 03:49 PM   #9
kp93300 is offline kp93300  Malaysia
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Default pictures

These are some pictures of the aleph j that I build.
The transformer is in another box.
The pre is J310 and Lightspeed clone as the attenuator.
hope i can find some pointers in troubleshooting this problem.

kp93300
Attached Images
File Type: jpg no 5.jpg (739.4 KB, 231 views)
File Type: jpg no 1.jpg (512.0 KB, 203 views)
File Type: jpg no 2.jpg (555.4 KB, 198 views)
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Old 27th November 2010, 04:13 PM   #10
kp93300 is offline kp93300  Malaysia
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Default more pictures

Some more pictures of the build
Attached Images
File Type: jpg no 3.jpg (549.2 KB, 191 views)
File Type: jpg no 4.jpg (656.9 KB, 177 views)
File Type: jpg img_3125.jpg (656.9 KB, 77 views)
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