aleph30 dc offset

[intense-tavda]

Hi there, I. am building an aleph30 to fullfill my needs for a total active system.
Now I got on the output on both channels 22,3Vdc, the mosfets on the + side are getting warm, the - side staying cold. The voltages on the channels on R37,38,39,35 and 36 are all between 22,4V and 22,8V only R34 gets 14,5V. Measuring 9610 gets between D-S gets 32,4V, 0,03V and 8,34V. Between G-D gets 28,4V, 14,2V and 13,8V. Between G-S is 3,9V, 14,2V and 5,4V. Anybody here can tell me whats going wrong? Thanks Teake

[Zen Mod]

Originally posted by intense-tavda
Hi there, I. am building an aleph30 to fullfill my needs for a total active system.
Now I got on the output on both channels 22,3Vdc, the mosfets on the + side are getting warm, the - side staying cold. The voltages on the channels on R37,38,39,35 and 36 are all between 22,4V and 22,8V only R34 gets 14,5V. Measuring 9610 gets between D-S gets 32,4V, 0,03V and 8,34V. Between G-D gets 28,4V, 14,2V and 13,8V. Between G-S is 3,9V, 14,2V and 5,4V. Anybody here can tell me whats going wrong? Thanks Teake

give us exact schematic , by which you made your amp ;

there are numerous schematics - designation wise .

gain transistors (- side ) are not opened enough ;

you must have more current through drain resistor on first input mosfet

[intense-tavda]

Hi Choky!
The boards are from Brian GT and I don't know the shematics I think its from Mark Gulbrandson, I will search for it, Teake

[intense-tavda]

I got on Q4 CE 8,8V and Q5 4,2V and on R11 9,1V, Teake

[Zen Mod]

Originally posted by intense-tavda
I got on Q4 CE 8,8V and Q5 4,2V and on R11 9,1V, Teake

compare this with your pcb .

then - using designation from this schematic , write what you measure

[Zen Mod]

Originally posted by Zen Mod



compare this with your pcb .

then - using designation from this schematic , write what you measure

edit :

if values are as on this schematic - you have systematic problem ,same on both channels

recheck orientation of parts etc

did you mounted input mosfets on some shared heatsink ?

[jacco vermeulen]

on R11 9,1V

For starters, the zener at the top, Z5, and the orientation of the irf9610 Q3.

[intense-tavda]

Hmm Jacco, could it be the bypass of the 2,2Uf filmcap on Z5? Teake

[Zen Mod]

Originally posted by intense-tavda
Hmm Jacco, could it be the bypass of the 2,2Uf filmcap on Z5? Teake

nope

[intense-tavda]

Here is the schematics I refer to