Aleph 5 problem - Page 2

pmchoong · 3rd November 2008, 03:11 AM

Output between gnd is measured at 35.42V

Manu · 3rd November 2008, 08:11 PM

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 ...

Manu

pmchoong · 6th November 2008, 06:49 PM

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.

pmchoong · 6th November 2008, 06:53 PM

My PSU is modeled after Krijistan's Aleph 5 PSU.
Output at 38.8V

pmchoong · 6th November 2008, 07:12 PM

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?

pmchoong · 7th November 2008, 01:04 PM

I am using 0.47/10 W for R22-25 and 1R/10W for R40-42 and R64-66
Would this be a problem?

pmchoong · 7th November 2008, 04:24 PM

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.

3rd November 2008, 08:11 PM	#12
Manu diyAudio Member Join Date: Nov 2002 Location: Vienna, Ostrich	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 ... Manu __________________ Manu, masked agent of entropy & ZMs Čiko

6th November 2008, 06:49 PM	#13
pmchoong diyAudio Member Join Date: Jan 2008 Location: Kuala Lumpur	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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3rd November 2008, 03:11 AM	#11
pmchoong diyAudio Member Join Date: Jan 2008 Location: Kuala Lumpur	Output between gnd is measured at 35.42V

6th November 2008, 06:53 PM	#14
pmchoong diyAudio Member Join Date: Jan 2008 Location: Kuala Lumpur	My PSU is modeled after Krijistan's Aleph 5 PSU. Output at 38.8V

7th November 2008, 01:04 PM	#16
pmchoong diyAudio Member Join Date: Jan 2008 Location: Kuala Lumpur	I am using 0.47/10 W for R22-25 and 1R/10W for R40-42 and R64-66 Would this be a problem?

7th November 2008, 04:24 PM	#17
pmchoong diyAudio Member Join Date: Jan 2008 Location: Kuala Lumpur	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.