Aleph 5 help please-32v at output

[AudioSan]

this is a Aleph5 andy.

 

[Andy5112405]

Even Aleph 5 will survive testing for a short period of time with one MOS-FET missing.
To be really safe, just reduce power rails to +/- 12V. Add a big resistor to kill the VCC rails.

 

[george a]

Hi Guys
Back for another round

I replaced one of the negative side output mosfets that was measuring a bit awry- result all 3 output fets measure 32v between the drain and source
I've taken this to be a positive sign
on the top end (positive) the voltage across the drain and source is zero for each of the fets.
offset at speaker terminals is now down to abt 0.48volts.
I think we're getting somewhere...

I'll now try pulling the top end fets out one at a time to see what happens...

Wish me luck..

 

[Andy5112405]

You want to measure the voltage across the Source Resistors, not D-S.

 

[Andy5112405]

0V across each +VE FET is not good, it indicates that they are all turned ON.

What is the voltage across each +VE FETs SOURCE resistor ?

 

[george a]

Hi again

speaker terminal offset is 32V
LED on board glows dimly


voltage across the source resistor (1.5ohm)- hopfeully that the one

is abt 3mV on the positve side and about 4mv on the negative side

Andy
how much for postage of 244 's to Australia

Cheers
George

 

[Bill Fuss]

George, your measurements must be in error, 0V across the top fets would cause the offset to be +32V.

What are your G-S voltages now?

 

[Bill Fuss]

We posted at the same time.

Don't mix 240s with 244s.

 

[george a]

Hi Bill

GS voltages
neg side 2.8v,0v,2.8v

pos side 2.9v,2.9v,2.9v

offest 32v

0v looks suspicious?

led dim

Hmmm

 

[george a]

I wouldn't mix the 244's with the 240's - looking at another amp.....

I tri amp my system ---2 X hafler dh200's + 1 aleph 5 clone

3 x the trouble....?

one of the haflers has a dead channel but all this current going one may allow me to repair it.

 

[Bill Fuss]

Actually, I don't like any of the G-S readings but 0V is a problem. Check to see if that resistor might be toast.

I'm assuming that is the fet you replaced. If not then I would replace all the fets in that group.

 

[george a]

Hi All

final result
one blown 240 on each rail
now running again using spare 240's left over from original build

To Nelson , Bill, Andy, Qusp and Audiosan,
A heartfelt thanks to you all for your assistance, you've all been great .
I hope I may someday be able to return the favour.
I think I've learnt a lot along the way.
I'm sure my wife would thank you too - now we can get back to normality.
Regards and good health to you all

George

Pay it forward.

 

[Bill Fuss]

That's great George, multiple failures, not the easiest thing to deal with.

 

[george a]

yes Bill

multiple multiple failures , ones of the new fets i put in was dead out of the box....

I'm going to bed now, enjoy your day.

 

[AudioSan]

Hi All

final result
one blown 240 on each rail
now running again using spare 240's left over from original build

To Nelson , Bill, Andy, Qusp and Audiosan,
A heartfelt thanks to you all for your assistance, you've all been great .
I hope I may someday be able to return the favour.
I think I've learnt a lot along the way.
I'm sure my wife would thank you too - now we can get back to normality.
Regards and good health to you all

George

Pay it forward.

glad you got it sorted out🙂 now, just sit back and enjoy the sound🙂
i'm looking forward to that day myself😀

 

[mat1976]

i think i am about to blow up my NEW aleph 5 amps.
if i build the PSU as suggested in schematic the i end up with 88.8 volts between +/-and around 44.4 volts between + and gnd or - and gnd.
my toroid is for 1 channel a 30/30V 5.7A.

please advice me on this problem.