Please look this schematic

[ketsada]

hello everybody
help me look schematic . why can not adjust VR1 = 30mA in PCB . but if test on curcuitmaker2000 can adjust no problem

Thanks you all a lot

[epmirafelix]

[IMG]C:\Documents and Settings\epmirafelix.PRICON.000\Desktop\50w[/IMG] ;


please try this.

Edwin

[epmirafelix]

instead of direct output from op amp put 1uF non polar capacitor.

[amplifierguru]

Hi Ketsada,
I don't understand. How can you monitor 30mA as there are no emitter resistors in the output.

The design is poor - it needs a 560R to supply from both driver collectors. They will define driver current and help HF discharge of the output transistors so you don't get dreaded cross-conduction (ask kanwar about this). Still the drop across the diodes may not be enough to bias the drivers on enough to turn the output stage on and you may need a small R in series with the diodes rather than across them. The chip will correct any offset. Really you need some small emitter resistors in the output stage for operating point stability, say, 0R22.

Cheers,
Greg

[ketsada]

thank Amplpfierguru

i will try to fix it