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Old 3rd November 2008, 03:11 AM   #11
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Output between gnd is measured at 35.42V
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Old 3rd November 2008, 08:11 PM   #12
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Its too much ...
(should less than 50mV)

Same issue on both channel?


Voltage accross R14 is near 0.
You don't have any current going through it, no voltage drop; so lower output mosfets don't conducts hence you get plain rail voltage (- 35V) at the output.

You could check if there is something wrong with R14 (to high res)

and/or Check Q1 and Q2
You should have about 4 V Vgs.
You could try to replace them, taking care of electrostatics ...

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Old 6th November 2008, 06:49 PM   #13
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Default same problem exist

I have canibalised the board, measured all resistors and zeners and re-soldered them back to a new board with new matched IRF 9610 and new MPSA18 transistors but the problem persisted. This is the measurement :

Output between gnd is measured at 43.3mV

R14 at 3.528V
MPSA 18 at Q4 measured at 3.525mV
MPSA 18 at Q5 measured at 11.7mV

R40 & 41 measured at 0.0
R42 at 0.7mV

R22 to R25 measured at 0.7mV

R11 measured at 5.12V
R14 at 3.528V

Z5 at 9.05V

Q3 IRF between G and S is measured at 3.93V
Q2 IRF between G and S measured at 3.79V

Q2 and Q3 mosfet warms up but not Q1

When I measured Q1 between G and S, a buzzing sound is audible at the speaker when I touch the G of the mosfet

Many thanks to those who help.
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Old 6th November 2008, 06:53 PM   #14
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My PSU is modeled after Krijistan's Aleph 5 PSU.
Output at 38.8V
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Old 6th November 2008, 07:12 PM   #15
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Quote:
Originally posted by Rodeodave


- Voltage across the output-FETs' source resistors and the FETs themselves (from drain to source)

- Voltage across the FETs of the CSS and the differential pair (also from drain to source)

- Voltage from drain of the IRF9610 in the CCS to ground

- Also please measure the supply voltages in reference to ground and the output-offset.

This should give some clues.
Q3 from drain to source is measured at 29.48V
Q2 from drain to source at 41.30 V
Q1 from drain to source at 37.8V

Q6-8 IRFP240 from drain to source measured at 37.5
Q18-20 IRFP240 from drain to source measured at 38.5V

How do I measured the drain of IRF9610 to ground?

Get the measurement from each IRF9610 between D and G from the star Gnd of PSU?
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Old 7th November 2008, 01:04 PM   #16
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I am using 0.47/10 W for R22-25 and 1R/10W for R40-42 and R64-66
Would this be a problem?
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Old 7th November 2008, 04:24 PM   #17
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I soldered R9 with a 220K resistor and R19 with a 220 resistor. Now when I turn on the amp, the LED lights up bright in a split of a second and then stay half dim. When turn off, the LED shuts out and then brightens up again with a very dim light. Also, when i turn on the amp, the speaker moves inwards and stay at that position. Thanks for help.
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