sajjad amer
Active Member
No, check the bias current - this will be a measurement taken across those emitter resistor pairs, with your multimeter set to read mV - instructions for this are in the SM - there are 2 settings per channel for this. ('hot side' bias current and 'cold side' bias current)
The reason for checking the bias is obviously to make sure it is set correctly, but also too much bias current could be the very reason why protection is still engaged. Too much bias current will cause more voltage to be dropped across the DBT bulb, thus lowering the available voltage to the protection circuit, thus possibly preventing it from disengaging.
Please do not remove the DBT until we can be sure that both channels respond correctly to DC offset and bias adjustment.
When we have verified this we will check what is preventing protection from disengaging.
I have checked the out put resistors and they check fine.
I'm not able to adjust the bias as when connected across the out put resistors the meter just reads zero.
I have 3 multimeters all of them read zero and the fuse inside the meter is fine.
Please see this picture the transistors marked in yellow become hot if I leave it on DBT.