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Old 18th April 2006, 06:46 PM   #1
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Default Aleph-x help me save it.

Hi everbody.

A few weeks back I was about to fire up my Aleph-x using Kristijans PCB
http://www.kk-pcb.com/alephx.html
Power supply
http://www.kk-pcb.com/power-x.html

I got strange readings. As didn’t want to burn anything started to dissemble everything measure everything and mounting it to the board again.
A few days back I did try it again and got these readings which where the same as before:

VARIAC 70V 110V 150V
T8 G-S 0V 0V 0V
T8 G-D 14V 21V 30V
T8 D-S 14V 21V 30V
R10 0V 0V 0V
R13 0V 0V 0V
R20 0V 0V 0V
R22 0V 0V 0V

I had the same measurements for T8, T9, T12, and T13
T8, T9, T12, T13 corresponds to Q2 and Q11 using Hifizens board
R10 R13 corresponds to R6

I did ask this question this question a few weeks back and Nelson Pass was kind to give me the solution:

“Not enough drive for T8 etc, or too much current through the
CCS transistors. If there's a lot of current (voltage across
Source resistors) then it's the latter. If not, then perhaps
there is not enough current going through the input diff pairs
to bias up T8 etc.”

Which made me realise I didn’t understand anything. So I started to read what could about the Aleph-x. Unfortunately I didn’t understand it all so couldn’t solve the problem.
So here I am.


What should I start looking for? Where should I start?

And please if you have any suggestions, be as specific as you can. It is much easier to understand if you say “you should try measure over R12 because….”etc.

Perhaps my power supply is no more and I have AC. But when measuring DC with DMM it looks ok.
Also perhaps Kristijans PCB is a scam but I don’t think so because reading all the threads about the Aleph-x it looks ok.
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Old 18th April 2006, 06:58 PM   #2
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It's very difficult to debug without component numbers on a schematic. If you have the KK schematic with these #, please post it.
What DC voltage do you read over the two 390 ohm resistors of the diff-pair?

/Hugo
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Old 18th April 2006, 07:12 PM   #3
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Hi Netlist.

Ah, I knew there was something I forgot to give you.
On the 390 ohm resistors I have 0V up to 150V.
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Old 18th April 2006, 07:33 PM   #4
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Now I'm confused. 150V?
What voltage is your power supply? What do you mean by variac 70V, 110V, 150V? AC or DC?

/Hugo
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Old 18th April 2006, 07:42 PM   #5
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Sorry. I mean 70, 110, 150 volt AC before the transformer.
Here are the corresponding DC values:

AC DC (after the caps on the power supply)
70V 6V
110V 11V
150V 15V
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Old 18th April 2006, 08:06 PM   #6
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OK, now I understand.
You will need to increase the voltage until the current source and the outputs turn on. What secundary voltage do you aim for at 230V? 22-0-22V like KK's schematic? Probably more as you seem to have 30V secundary with 150V primary.
If the voltage over the two 390 R's is 0V, the diff-pair is not working.
What is the voltage over the 9.1V zener in the current source and what are the voltages at the FET, I think T4?

/Hugo
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Old 18th April 2006, 08:28 PM   #7
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If I haven’t made any mistake the power supply is the same as the schematic. If I measure on the power supply between ground and minus it seems to be ok. Perhaps I made a mistake when connecting + - and ground?
If I understands this. The (+) on the power supply should go to (+) on the pcb and the same for (-). Ground on the pcb doesn’t need to be connected right now, but of course later. Ground from the power supply doesn’t need to be connected right now.
The voltage over T4 (Q6 Hfizen) and the zener is 0V.
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Old 18th April 2006, 08:48 PM   #8
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Sure you need ground to be connected. Tell us what happens when you did connect it. Do you have a link to the Hifizen schematic? I'm honestly too lazy to search.

/Hugo
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Old 18th April 2006, 09:25 PM   #9
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Wow it made all the difference.’

Here are some measurements

6V (DC)
T8
G-S 2,2
G-D 7
D-S 9,2

R10 0V

R36 2,12
R31 2,21
Zener 6,4

T4
G-S 3.9
G-D 3,8
D-S 0,1

As for Hifizens schematic it’s the same numbering system as Grey’s. I’ve just looked at the wiki http://www.diyaudio.com/wiki/index.php?page=Aleph-X
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Old 18th April 2006, 09:31 PM   #10
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It's bedtime here.
Carefully increase the voltage and look if nothing starts smoking.
Make sure the output mosfets are well isolated from the heatsinks
and properly attached. Monitor the DC voltage at the output with respect to ground.

/Hugo
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