DD Z2 bursts output transistors

[yoppi]

Can it be worth?

 

[Perry Babin]

Take the scope off of auto and set the vertical amp and timebase manually.

 

[yoppi]

Can it be worth?

 

[NadaD]

Set AC couple and try to adjust manually again

 

[Perry Babin]

It's possible that there are no waveforms but it appears that the scope sees an 11v waveform. First, see if you can get a good display on your input signal (from the signal source).

 

[yoppi]

the signal is taken directly from pin 6 of irs21844. in the 4 they are equal. with AC coupling the pulse is the same.

 

[Perry Babin]

This is from a different amp but you can see the what the waveforms should look like. This is from a fully functioning amp so the frequency is much greater. The amplitude is approximately what you should see.

 

[yoppi]

I understand that the pulse is very weak. I have tried another handheld oscilloscope and I have the same pulse.

 

[Perry Babin]

With the handheld scope, black probe on source leg, red on gate leg, vertical amp set to 5v. Timebase set to whatever it takes to clearly display a few cycles. is the signal still weak?

Do you have 12v on the VCC terminal of the 21844s? Black meter probe on anything connected to the negative rail.

 

[yoppi]

I have performed the test (black probe on source leg, red on gate leg, vertical amp set to 5v) I get the same weak pulse as always. the voltage on leg 7 of irs21844 is 12v on all 4

 

[Perry Babin]

DC voltage on pin 2 of any of the 21844s?

 

[yoppi]

3.60vdc on pin 2 above negative rail

 

[Perry Babin]

Do you see a square wave on pin 1 when you drive a signal into the amp? About 10v amplitude above the negative rail?

 

[yoppi]

pulse on pin 1

 

[yoppi]

Any idea??

 

[Perry Babin]

When you drive a signal into the amp, do you have a square wave swinging plus/minus 5v on the output of the LM211? (U4)?

 

[yoppi]

yes, at the LM211 output there is a square wave and 4.85v

 

[Perry Babin]

positive AND negative 4.8v?

Do you see essentially the same signal on the emitters of Q1 and Q3?

Do you see essentially the same signal on one end of the resistors R37 and R42?

 

[yoppi]

image corresponds to pin 7 of LM211

 

[yoppi]

image corresponds to emitters of q1, q3, and one end of the resistors R37 and R42.