aleph5 question

rwagter · 6th March 2005, 05:24 PM

I build an A5 some 2-3 years ago and it works like a clock (usually)

Today I listened to some low level music and it seemed that one speaker was completely dead. When fumbling with the speaker terminals it seemed that one off the connections was somewhat instable (it was completely lose inside and it bearly made contact and I never noticed before

)

So when I had done some resoldereing I couldn't resist taking some measurement and I noticed something strange...

1 channel draws 35V/10,7A at the powersupply while the other draws 35V/6.07A.
DC offset at the terminals is 38mVand 10mV.
So I measured some more, the fets are running at 2.87A both channels and voltage is also the same (0.6 V). When connected to a sinewave generator output is the same with an 8ohm resistor.

Can someone explain where those 4 amps are going ???

Ralph

Netlist · 6th March 2005, 05:31 PM

Four amps is a lot!!
I have to ask: Are you sure the measurement is correct?

/Hugo

rwagter · 6th March 2005, 05:34 PM

A checked, rechecked, triple checked and still couldn't believe it because 4 amps at 35V is 140W ?!!!

Netlist · 6th March 2005, 05:41 PM

What about the heat on both channels?

/Hugo

rwagter · 6th March 2005, 06:41 PM

That more or less the same, which it should be since the fets are burning the same amount of V.A

Netlist · 6th March 2005, 07:29 PM

Is it an exact copy of the Pass Aleph5 or did you modify it?
I mean add chokes or SMPS or...?

/Hugo

Stuart Easson · 6th March 2005, 07:50 PM

there are 2 options I can think of, assuming totally separate PSUs, check your rectifiers, and then check your caps, I had one that was not a dead short, but close to it, and given long enough it would have gone poof...I found it after noticing it was getting warm...

Stuart

rwagter · 6th March 2005, 08:51 PM

Stuart,

I will check your option though that will be !@$%!% since I used 12 smaller caps per channel And will have to unsolder them one at the time !!

Hugo,

it's a standard A5 but completely dual mono so I'll check the caps first

Ralph

Stuart Easson · 6th March 2005, 08:54 PM

...check with your meter for the resistance of the bank as a whole. After a while it should approach a huge number, the meter has to charge all the caps, but if one is bad it will not climb past a certain point...if it shows up as shorted, then you can start unsoldering...

Stuart

wuffwaff · 6th March 2005, 08:58 PM

or just disconnect the amps and power up the supply. If you still have some current running you´ll know where to look.

William

6th March 2005, 05:24 PM	#1
rwagter diyAudio Member Join Date: Jul 2002 Location: Netherlands	aleph5 question I build an A5 some 2-3 years ago and it works like a clock (usually) Today I listened to some low level music and it seemed that one speaker was completely dead. When fumbling with the speaker terminals it seemed that one off the connections was somewhat instable (it was completely lose inside and it bearly made contact and I never noticed before ) So when I had done some resoldereing I couldn't resist taking some measurement and I noticed something strange... 1 channel draws 35V/10,7A at the powersupply while the other draws 35V/6.07A. DC offset at the terminals is 38mVand 10mV. So I measured some more, the fets are running at 2.87A both channels and voltage is also the same (0.6 V). When connected to a sinewave generator output is the same with an 8ohm resistor. Can someone explain where those 4 amps are going ??? Ralph

6th March 2005, 07:50 PM	#7
Stuart Easson diyAudio Member Join Date: Oct 2002 Location: Santa Cruz, CA	an idea... there are 2 options I can think of, assuming totally separate PSUs, check your rectifiers, and then check your caps, I had one that was not a dead short, but close to it, and given long enough it would have gone poof...I found it after noticing it was getting warm... Stuart

6th March 2005, 08:54 PM	#9
Stuart Easson diyAudio Member Join Date: Oct 2002 Location: Santa Cruz, CA	first... ...check with your meter for the resistance of the bank as a whole. After a while it should approach a huge number, the meter has to charge all the caps, but if one is bad it will not climb past a certain point...if it shows up as shorted, then you can start unsoldering... Stuart

6th March 2005, 08:58 PM	#10
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	or just disconnect the amps and power up the supply. If you still have some current running you´ll know where to look. William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

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6th March 2005, 05:31 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Four amps is a lot!! I have to ask: Are you sure the measurement is correct? /Hugo

6th March 2005, 05:34 PM	#3
rwagter diyAudio Member Join Date: Jul 2002 Location: Netherlands	A checked, rechecked, triple checked and still couldn't believe it because 4 amps at 35V is 140W ?!!!

6th March 2005, 05:41 PM	#4
Netlist diyAudio Moderator Join Date: Jan 2003	What about the heat on both channels? /Hugo

6th March 2005, 06:41 PM	#5
rwagter diyAudio Member Join Date: Jul 2002 Location: Netherlands	That more or less the same, which it should be since the fets are burning the same amount of V.A

6th March 2005, 07:29 PM	#6
Netlist diyAudio Moderator Join Date: Jan 2003	Is it an exact copy of the Pass Aleph5 or did you modify it? I mean add chokes or SMPS or...? /Hugo

6th March 2005, 08:51 PM	#8
rwagter diyAudio Member Join Date: Jul 2002 Location: Netherlands	Stuart, I will check your option though that will be !@$%!% since I used 12 smaller caps per channel And will have to unsolder them one at the time !! Hugo, it's a standard A5 but completely dual mono so I'll check the caps first Ralph

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