This amp came with shorted outputs so I replaced them and the IR2110S. With the outputs in the amp I have rail to rail oscillation but it goes from 140volts to 40 volts and starts to draw 9 amps. With the outputs out I don’t get any low side drive unless I short pins 6&7 on the TL072.
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What's the rail voltage with no outputs in the amp?
Does the secondary ground remain at 0v when the rail-rail swing is +140v to -40v?
It's normal to have to bridge pins 6/7 (output to inverting input) of the feedback op-amp to have both high and low drive.
Does the secondary ground remain at 0v when the rail-rail swing is +140v to -40v?
It's normal to have to bridge pins 6/7 (output to inverting input) of the feedback op-amp to have both high and low drive.
With no outputs the rail voltage is +-134. For secondary ground would I use the RCA shields or negative speaker terminal?
The RCA shield may not be ground in this amp. The negative speaker terminal is likely a better option.
Confirm that the negative speaker terminal reads 0 ohms to the secondary windings of the power transformers.
Confirm that the negative speaker terminal reads 0 ohms to the secondary windings of the power transformers.
Yes the negative speaker terminal is secondary ground. With rail to rail oscillation it is .431 volts on the negative terminal.
Did you remove the jumper on pins 6/7 of the op-amp?
Is the amp producing clean audio?
What ground were you using when you had a r-r oscillation of -40 to 140v?
Is the amp producing clean audio?
What ground were you using when you had a r-r oscillation of -40 to 140v?
Yes I removed the jumper on the feedback op amp. I turned the amp over and seen a 1 ohm resistor across R180 and removed it due to not looking like a factory modification and the amp produced normal rail to rail oscillation. I Checked that 1 ohm resistor out of circuit and it’s reading 1 million ohms. I’m not sure why this was added R180 is an 270K ohm resistor.
With no rail to rail oscillation there is 3 volts offset. With rail to rail oscillation there is 0 volts. The amp isn’t producing audio, it starts oscillating at 140 volts then goes to 40 volts like before while drawing 9 amps of current.
Using the negative speaker terminal as the ground for the scope, do you still see a -40v to 140v swing on the input of the output filter inductor?
The issue was caused due to the replacement outputs I was using. They had a significant lower gate charge rating than the original outputs.