Completed aleph J --loud cracking sound on switch off

kp93300

Member
2007-03-21 7:00 am
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
 

kp93300

Member
2007-03-21 7:00 am
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 0.1µF "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
 
considering this :

To power off, I pull the power cord from the ac receptacle and the problem persisted.
kp93300


this will not help :


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
 

kp93300

Member
2007-03-21 7:00 am
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
 

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kp93300

Member
2007-03-21 7:00 am
power supply for aleph J

Hi Zen Mod,
There is a slow start board and CL 60 before the 500W 18 0 18 0 V ac transformer.
One transformer for both channels.
C L C filtering. The trans and first C is shared with another amp---F5. There is no such problem with F5.
The L( inductor ) and C is recently diyed for the AlephJ. I have one L for the +Ve and one L for the -Ve. The + and- ve rails are shared with both channels.
The amp sees 21 V dc on load and measure the same for both channels.
many thanks

kp93300
 

Rodeodave

Member
Paid Member
2004-12-26 9:38 pm
in the alps
Don't most Alephs do that? There were various discussions on that in the past. I believe it has something to do with the +/- rails not draining equally fast when the power is cut. Maybe different value bleeder resistors can minimize the effect. I didn't bother with my Mini Aleph though since my speakers seemingly are okay with it.