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Old 22nd April 2006, 07:37 PM   #1
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Default debuging aleph x

Hi all,

I have a little prolem with my aleph X.

Here is the problem i face :

I power on my aleph X. Power supply provides around 21Vdc to the board. Voltage through all source resistors is 0.5V , all is heating nicely until 30 seconds after power on.

The power supply voltage drop to 8 V and MOSFETs (IRF240) stop heating.!!

What is this?? What's wrong with my Amp?

Thanks for your help in advance

Loic

schematic i use enclosed + PCB i have
http://jppelan.free.fr/HC/ALEPH_X/ax-pcb.jpg
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File Type: pdf a-x_10sch.pdf (23.7 KB, 151 views)
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Old 22nd April 2006, 08:15 PM   #2
jleaman is offline jleaman  Belgium
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I'm going to follow this because i have a set of these boards also.
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Old 22nd April 2006, 10:58 PM   #3
sbear is offline sbear  United States
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I'd put down at least even money that it's something in the power supply. Can you post a schematic and maybe even a pic of the PS?
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Old 23rd April 2006, 07:18 AM   #4
Netlist is offline Netlist  Belgium
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Loic,
Are the capacitors in the PSU correctly wired? How is your ground connected? Does the PSU keeps it's voltage when disconnected from the amplifier?

/Hugo
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Old 23rd April 2006, 07:14 PM   #5
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Default debuging aleph x

here the picture of my PSU. i have recifier ( 18Vac - BYW99 200 then 47000F then 0.1R then 33000V )

I Tried to run my PSU not connected to the Board : It keeps 24.5V on V+ and V- with a difference of 0.05V betw. V+and V- voltage.
Voltage do not drop even after minutes working (not connected to the board).

Loic
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Old 23rd April 2006, 08:09 PM   #6
Netlist is offline Netlist  Belgium
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Loic,
the big alu plate you used seems to be dangerously close to the +. Watch out!
If there were a short, the PSU wouldn't work on his own.
This is how I wired the PSU in my AlephX:
http://www.diyaudio.com/forums/showt...297#post194297
The main difference is other rectifiers, and a CRCRC instead of CRC in your amp. Can you confirm the similarities and the way you wired up your Aleph? The ground connection should of course go the star ground of the PCB.
Is this power supply for both channels or only one monoblock?

/Hugo
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Old 23rd April 2006, 08:44 PM   #7
Blues is offline Blues  United States
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Is that 0.1R connected to Ground from the + of 47mF cap? If so then it is not connected right. It should be between + 47mF and + 33mF for a CRC power supply.
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Old 23rd April 2006, 09:23 PM   #8
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Default debuging aleph x

netlist

Yes my PSU is looking like yours.

here my schematic :
http://s37.photobucket.com/albums/e9...nt=LOIC_PS.jpg

I replace capacitors by 1* 33000 then 0.1 R then 47000f
Other items of my PSU are identical to the schematic

thermistance is a 22 ohm. My PSU is for both channels.

I connect the ground of PCBs to the aluminium plate ground.

V+ of the pcb to + of capacitor(red cross on my PSU photo)
; - of capacitor screwed on alu plate

V- of the pcb to - of capacitor(red - on my PSU photo)
; + of capacitor screwed on alu plate


For information :

Wtih Vr2 at 140 Ohm and Vr1 /Vr3 at 0 ohm
i measured (few second after power on)
between PCB ground and OUT + : 10v decreasing with time
between PCB Ground and OUT- : 5v decreasing with time

Loic
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Old 23rd April 2006, 09:23 PM   #9
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Default debuging aleph x

Blues

In order to lower risks i have connected only the 47000F capacitor, not using the 33000f for the moment.


So i have + 18Vac from transfo to the rectifier input then rectifier output to 0.1R then 47000f. Resistors are NOT connected to ground plate.

That mean, for the moment , i'm in a RC configuration.

Is it a problem source?

Loic
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Old 23rd April 2006, 10:00 PM   #10
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What's your NTC ? Rated for your primary current ?
Does the Xformer heat up during the first 30 s of normal behavior ?
Any info about a thermal fuse in the trafo ?
Unplug the amps from the supply, remove (bridge) the NTC, and hook up some power resistors to the supply's output, in order to draw the same current than the amps. Does the strange behavior still show up ?
Same thing when the NTC's in ?
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