Aleph mini one channel not working

[yoke]

Aleph mini one channel not working

Hi
I have put together two channels of Aleph Mini, couple months ago. ( based on Brians GB PCB and curcuit )

But some how I manage to destroy one channel. I believe that, during the operation under voltage, PCB have touched aluminum bar under it, and now I have 18V (power supply voltage) on the output.

I was hoping that, only, fault would be destroyed output mosfets but they are fine, they still work (I have check them by procedure described in here http://www.bcae1.com/ampfail.htm ). But I replace them any way (for some other reason)

So does any one have any idea what could be wrong in the circuit that would produce power supply voltage on the output?
Since I have no experience in fixing power amps ;-) and have no equipment for that, except one multimetar ;-)

thanks

 

[sandstorm33]

If all mosfets are "good" including front end devices I would check Q4 and C2 and C3.

 

[yoke]

Hi sandstorm33...thanks for replay
I haven't check front end mosfets, I’m hoping that I will not need to desolder them since it will be very difficult to solder them back in the place...

will see if any one else have some other idea, what could be wrong...
have to see if I have some spear ZTX450...

 

[yoke]

I have replace bouth ZTX450 and I still have +18V on the output...

 

[yoke]

o.k.
I have found one folt,broken resistor...R27 (0.5 5W )

http://diyamps.com/aleph/docs/miniAleph-sch.pdf

could it be it ?
I mean if I replace only this one resistor, everithing should work, or should I try to find if there's something else broken.
what should I check that could be relate with broken R27 ?

 

[sandstorm33]

o.k.
I have found one folt,broken resistor...R27 (0.5 5W )

http://diyamps.com/aleph/docs/miniAleph-sch.pdf

could it be it ?
I mean if I replace only this one resistor, everithing should work, or should I try to find if there's something else broken.
what should I check that could be relate with broken R27 ?

R27 broken (or burnt) would cause the output to see+18volts . If you checked the OUTPUT MOSFETS and thet are good than you should be OK after replacing R27.

 

[yoke]

I have replace R27 and now everything works...well I didn't conect input or speakers but multimeter at the output says 0.022V...;-)

Thanks sandstorm33

 

[sandstorm33]

I have replace R27 and now everything works...well I didn't conect input or speakers but multimeter at the output says 0.022V...;-)

Thanks sandstorm33

Cant get much better than that!!!!