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.
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.
Thago said:
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 ?
Thago said: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
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.