2 Monoblock Class Ds Not Working, I'm Lost

[Perry Babin]

Why is it in protect?

That's the emitter of the driver. I need to see the base.

The first scope settings are much better.

The the output on most class D amps, 0.2v/div is picking up noise and is mostly useless.

 

[D132]

Which pin is the base?

Sometimes it starts in protect sometimes it doesn’t, not sure what the differentiation is

This is the output when it wasn’t in protect (took this after previous post)

 

[Perry Babin]

0.2v/div is useless for most all class D amps.

Look up the datasheet if you don't know the pin configuration of any component. For most small transistors with an A, B, C or D prefix, the pin configuration is ECB. Look up the datasheet to confirm the configuration.

Do you have any 1k resistors?

 

[D132]

I realized it only goes into protect when I have my scope on as I turn on the amp.

This is the pin across from the previous which is base after checking datasheet

Yes, I have a few

 

[Perry Babin]

Previously, the duty cycle was near 50%. Now it's very low. The difference may be that the amp was having trouble starting when your scope was causing problems.

Did you mean 'on' as in the scope was powered up or 'on' as in having your probe connected to the amp?

Reduce the 12v supply voltage. Can you force the amp to full duty cycle before it shuts down?

Leave the supply providing the remote voltage at the same voltage as it is now.

 

[D132]

On as in scope powered up

I’m not sure how I would do that

I have my 40amp power supply powering it right now at 13.5v.

I have a second supply which I had shown previously.
I can hook both of them up, supply remote with 13.5v with the lower power supply, and lower my 40a supply to 12v, is this what you mean?

I cannot use the original supply for power as it is 3a max and the amp will not power on with that

 

[Perry Babin]

Do whatever you have to do with whatever you have to keep the remote voltage steady and lower the voltage feeding the main B+ and ground. You may have to go lower than 12v. Go as low as you can until you get back to 50% duty cycle.

 

[D132]

I will most likely use the 2 power supplies. If I do will I need to connect both to the amplifier ground/negative connection?

 

[Perry Babin]

The grounds will need to be connected.

 

[D132]

Remote around 13.5v, power around 12.7v

 

[Perry Babin]

If you lower the B+ supply, does the pulse width increase?

Does the idle current increase as you get down to approximately 10.5v?

 

[D132]

B+ power supply is remote?

10.5v remote or power?

 

[Perry Babin]

The supply feeding the large terminal is what you want to reduce. Not remote. We are using two supplies because low remote voltage was causing problems with this amp.

 

[D132]

12v remote, B+ is at 10v

Pulse width gets wider, idle current increases with lower B+ voltage

 

[Perry Babin]

Is it still having problems powering on?

 

[D132]

No, but it still goes into protect when any sort of signal is passed. Swapped RCA plate from parts amp and same result.

I am using my phone with an aux to RCA cable adapter as a tone generator. I have a spare headunit I can use to see if it still goes into protect, do you think that would cause any change?

 

[Perry Babin]

Some amps do strange things when driven with a signal source that has no grounded shield.

 

[D132]

Should I connect the RCA ground to power ground?

 

[Perry Babin]

By having the ground of the head unit connected to the PS that's powering the amplifier, the RCA shields should read 0 ohms to the PS ground with no other connections.

 

[D132]

Should I also connect the amp RCA ground to PS ground?