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.
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.
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
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
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.
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.
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
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
A crucial point to measure is the voltage over both resistors R23 and R25. Between 4 and 5V will make the gain mosfets turn on.
You need enough rail voltage to achieve this, I believe something like 12-0-12 is a minimum. What rail voltage are you aiming for with a 230V supply? Check the DC voltage from out+ and out- to ground. It will vary with different rail voltages so you can only adjust it properly when the nominal voltage is reached.
/Hugo
You need enough rail voltage to achieve this, I believe something like 12-0-12 is a minimum. What rail voltage are you aiming for with a 230V supply? Check the DC voltage from out+ and out- to ground. It will vary with different rail voltages so you can only adjust it properly when the nominal voltage is reached.
/Hugo
Ok. After numerous different problems I’ve started it up again. When turning up to about 14V I have 4,7V on Q1 and Q10 (using HifiZens numbering system, those Q on the top of the schematic). 4,4 V on Q2 but on Q11 I have only 1,2V (bottom left). On R23 I have only 1,2V and on R25 I have 4,9V. This isn’t ok I think. What should I look for?
Yes. I had a bad transistor (Q11). Thanks.
Another curious thing is happening. When turning on the Q2 and Q11 is turning on evenly. But after a few seconds they both is lowering the voltage. After a few minutes Q2 stops at about 4 V when using 12V from the power supply but Q11 never stops lowering its voltage. I stopped when I had about 3V. What should I look for?
Another curious thing is happening. When turning on the Q2 and Q11 is turning on evenly. But after a few seconds they both is lowering the voltage. After a few minutes Q2 stops at about 4 V when using 12V from the power supply but Q11 never stops lowering its voltage. I stopped when I had about 3V. What should I look for?
If I remeber it correctly its about 24V. The scematic is here: http://www.kk-pcb.com/power-x.html
Try increasing the voltage. Good chance the amp stabilizes.
Make sure the mosfets are well cooled and try to trim the DC voltages at the output to a minimum. +/- less than 1 volt output to ground and less then 100mV between both outputs.
You are aware of the existence of the WIKI page are you?
/Hugo
Make sure the mosfets are well cooled and try to trim the DC voltages at the output to a minimum. +/- less than 1 volt output to ground and less then 100mV between both outputs.
You are aware of the existence of the WIKI page are you?
/Hugo
Ok
Here comes next problem. Q11 turns up much later then Q2. When I have about 2V on Q2 I have 0V on Q11. Turning on full voltage I won’t get over 4V on Q11. I have about 4,6V on Q2 as it should be. So far I have changed Q2, Q11 and Q5, Q7 measured R23,R25, changed all the 5W resistors. Anybody knows what to look for?
Here comes next problem. Q11 turns up much later then Q2. When I have about 2V on Q2 I have 0V on Q11. Turning on full voltage I won’t get over 4V on Q11. I have about 4,6V on Q2 as it should be. So far I have changed Q2, Q11 and Q5, Q7 measured R23,R25, changed all the 5W resistors. Anybody knows what to look for?
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