Digital Designs C4.100 150 mv Dc offset

[Perry Babin]

When you drive the amp into a load, does the voltage on the collector of the NPN outputs drop significantly (more than the good channel)?

 

[stark industries]

When I coducted the test with the loads only at low volumes the other half of the wave was missing. When I turned the gain up it formed this wave.

 

[Perry Babin]

Heat and cool (inverted can of computer/keyboard duster) the bias transistor (may have to lift it off of the heatsink) to see if it makes a difference in the distortion.

When testing, you need to change one variable at a time. Changing the gain position changed both the position of the control AND the output level. That makes it difficult to know which made the difference.

 

[stark industries]

Voltage is the same in the collector of the NPN transistor in the bad channel compared to the good channels when the amp is driving a load.

 

[stark industries]

Amplifier was taken of the heat sink and heat was applied to the transistors, it was then allowed to cool. The DC in the output began to rise and when the heat was turned of it decreased slowly.

 

[Perry Babin]

Just heat/cool the bias transistor and watch the distortion while driving the load.

 

[stark industries]

Distortion was the same as the previous scope pic I sent.

 

[stark industries]

YouTube this is exactly how my speakers sound.

 

[Perry Babin]

To clarify, are you saying that heating the bias transistor or cooling it to a point where there is ice on it produces absolutely no change in the distortion seen on the scope (as in post #22)?

 

[stark industries]

Hello Perry, sorry for the late response. The problem was a dirty gain pot which was operating the gains on channels 1&2. Do you know where I can find a replacement for this or is there anyway that this can be cleaned?

 

[Perry Babin]

Mouser may have something suitable. Deoxit D5 works pretty well for cleaning pots (assuming that they are not damaged internally).