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Old 2nd November 2007, 09:03 PM   #1
Thago is offline Thago  Belgium
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Default Aleph 2 Current devices: which voltage?

Hi

I am building a pair of Aleph 2 amps. After toroughly testing the power supply, which provides a clean +/- 45V on both rails, I hooked up my first main PCB (I'm using KK-PCB's), and measured the voltage between the D and the R outputs, as well for the constant current as for the gain devices. Results are: 2.3V for the constant current outputs, and 89.5V (= full power supply voltage) for the gain devices. Would this be correct?
Thanks in advance for replying.
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Old 2nd November 2007, 09:48 PM   #2
Thago is offline Thago  Belgium
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Some more explanation: D = drain, R = Source.
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Old 2nd November 2007, 09:48 PM   #3
Zen Mod is offline Zen Mod  Serbia
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Default Re: Aleph 2 Current devices: which voltage?

Quote:
Originally posted by Thago
Hi

I am building a pair of Aleph 2 amps. After toroughly testing the power supply, which provides a clean +/- 45V on both rails, I hooked up my first main PCB (I'm using KK-PCB's), and measured the voltage between the D and the R outputs, as well for the constant current as for the gain devices. Results are: 2.3V for the constant current outputs, and 89.5V (= full power supply voltage) for the gain devices. Would this be correct?
Thanks in advance for replying.

gain devices aren't biased ; your input diff pair isn't good or their CCS ;

that presuming that all solder joints and wiring are good

goal is to have 0 volts at output , not some magical amount of volts across lower or uper mosfets
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Old 2nd November 2007, 10:11 PM   #4
Thago is offline Thago  Belgium
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Hi, thank you for replying. Could you please explain to me what CCS exactly means?
How could I check the bias of the gain devices?
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Old 2nd November 2007, 10:27 PM   #5
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You might try getting in touch with the guy who sold you those boards. If he's making money selling you boards, he should support them.
CCS means Constant Current Source.

Grey
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Old 2nd November 2007, 10:30 PM   #6
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Thago
Hi, thank you for replying. Could you please explain to me what CCS exactly means?
How could I check the bias of the gain devices?

look at attached pdf - wonderful work of our fellow DiyA ;
you'll find many explanations in .


input diff pair (left side of circ ) is made with two small mosfets (just disregard that this pdf is for A30 - almost all Alephs are the same) , and they are fed with current through one mosfet above them ;

that mosfet ,along with few parts ( zenner, resistors) form CCS - that' acronym for Constant Current Source , and role of that funny creature is to push exact amount of current thriugh load,whatever his inner resistance is in moment ;

half of current goes through Q101 (look at pdf all the time) and through R9 ; current through is forming voltage of ~ 4Vdc , and that voltage is what is needed to entirely open your lower bank of output mosfets ........ in pdf they're marked as Q106,107 and 108

point is if you don' have ~4V from G to S of mentioned output mosfets , they have high inner resistance (D to S) , and poor output CCS ( formed of upper bank of output mosfets, here Q103,104,105) try really hard to pump adequate current through closed lower mosfets ............ all they (in CCS) have as tool is to increase voltage sky high , trying to pump that current ;

mebbe they will succeed if you crank PSU voltage to 300+ volts , but I think that is somehow better to repair input CCS (Q3 and related parts )

clearer now ?

Attached Files
File Type: pdf aleph30.pdf (29.9 KB, 82 views)
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Old 2nd November 2007, 11:15 PM   #7
Thago is offline Thago  Belgium
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Hi, it's absolutely clear now
If I understand it right, the IRF9610's I use have a (too) high internal resistance? I'm using 9610's from IR, they are easy to acquire. Would than the solution be to use better 9610's? Are Samsungs better than IR?
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Old 2nd November 2007, 11:28 PM   #8
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Thago
Hi, it's absolutely clear now
If I understand it right, the IRF9610's I use have a (too) high internal resistance? I'm using 9610's from IR, they are easy to acquire. Would than the solution be to use better 9610's? Are Samsungs better than IR?
nope

you mixed things from other thread - where Papa answers to you ;

point with IR- Harris difference is that later have smoother transfer characteristic

your problem is that gain devices on output ( output mosfets ) aren't opened

measure voltage from minus rail to their gates and tell us


print that pdf in 30 copies , then take them with ya next 3 days, until you tear them of looking at......... that way you'll understand each part's role .......

at least - that's how I learned that .

re-read few times what I wrote ;
everything is in there
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