AC where it shouldn't be.

anders.a · 7th February 2006, 09:06 PM

Connecting to the Aleph-X pcb. I have AC on the pwr supply. Is this ok? Also I have to much voltage on Q2 and Q11. Measured about 12V without turning on the variac to 220V.

BobEllis · 7th February 2006, 10:14 PM

How much AC is on the rails? a few volts or a few millivolts?

Do you have the DC that you expect when the PSU is not connected to the amp? describe your psu - CRC? how much C and R?

What is your expected rail voltage?

What voltage do you get over R23 and R25? If less than ~4V you won't turn on Q2/Q11 and their drains will be close to the positve rail.

anders.a · 7th February 2006, 10:28 PM

Several volts AC.
I have 18VDC as expected. I'm using this power supply: http://www.kk-pcb.com/power-x.html

As I´m using this board http://www.kk-pcb.com/alephx.html I have to come back tomorrow for the voltage over R23 and R 25

BobEllis · 7th February 2006, 10:56 PM

If you're getting that much AC then something is seriously wrong. Something is drawing a ton of current, you should be seeing millivolts with that filter. check for a solder bridge to ground or across the rails, backwards electrolytic or backwards FET.

The part numbering I was using refers to Grey's schematic. R23/25 are the 390R in the legs of teh LTP.

7th February 2006, 09:06 PM	#1
anders.a diyAudio Member Join Date: Dec 2004 Location: Sweden	AC where it shouldn't be. Connecting to the Aleph-X pcb. I have AC on the pwr supply. Is this ok? Also I have to much voltage on Q2 and Q11. Measured about 12V without turning on the variac to 220V.

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7th February 2006, 10:14 PM	#2
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	How much AC is on the rails? a few volts or a few millivolts? Do you have the DC that you expect when the PSU is not connected to the amp? describe your psu - CRC? how much C and R? What is your expected rail voltage? What voltage do you get over R23 and R25? If less than ~4V you won't turn on Q2/Q11 and their drains will be close to the positve rail.

7th February 2006, 10:28 PM	#3
anders.a diyAudio Member Join Date: Dec 2004 Location: Sweden	Several volts AC. I have 18VDC as expected. I'm using this power supply: http://www.kk-pcb.com/power-x.html As I´m using this board http://www.kk-pcb.com/alephx.html I have to come back tomorrow for the voltage over R23 and R 25

7th February 2006, 10:56 PM	#4
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	If you're getting that much AC then something is seriously wrong. Something is drawing a ton of current, you should be seeing millivolts with that filter. check for a solder bridge to ground or across the rails, backwards electrolytic or backwards FET. The part numbering I was using refers to Grey's schematic. R23/25 are the 390R in the legs of teh LTP.

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