Kicker ZX750.1 Makes Squealing sound when powered up

[Perry Babin]

Why was the amp taken out of the vehicle to be repaired?

 

[bigpun4fubu]

no audio , i had replaced the LM361 previous then it had audio but squealed i have checked the current with my regular multimeter and it read a 2 amp current draw but then i got a dc clamp meter and noticed it is pulling excessive current

 

[Perry Babin]

Are you sure that the clamp meter is accurate?

What meter were you using that read 2 amps?

 

[bigpun4fubu]

a craftsman autoranging multimeter 82139, the clamp meter is a craftsman 400A ac/dc clamp meter 82369

 

[bigpun4fubu]

its brand new and has been accurate on other stuff ive tested

 

[bigpun4fubu]

i also dont think the caps by the positive and ground terminals should get hot at idle nor the transformer

 

[Perry Babin]

Post the waveforms on the gate leg of one of the power supply FETs when the amp is drawing 10 amps. Set the coupling to DC. Align the trace to the center reference line. Set the vertical amp to 5v/div and the timebase to 10us/div. Adjust the timebase to display approximately 3-4 complete cycles if that's not what you see at 10us.

 

[bigpun4fubu]

this is what i get on all gates

 

[Perry Babin]

The scope wasn't triggering properly but from what I can see, it's OK. What are you using to power the amp?

 

[bigpun4fubu]

30 amp dc power supply set at 13.8 volts there is ghosting in the background of wave form , that is the squealing it goes away for a sec when the squealing stops for a second and then i recycles back over

 

[Perry Babin]

When it squeals, it's producing some sort of electrical noise that's causing the problem with triggering.

If you touch the scope probe to the positive power terminal when it's squealing, does the trace get fuzzy?

 

[bigpun4fubu]

yes

 

[bigpun4fubu]

but it also squeals on a car battery

 

[Perry Babin]

Set the timebase to 2ms/div. What does the trace look like on the B+ terminal when it squeals?

 

[bigpun4fubu]

 

[Perry Babin]

If you have a ground clip for your scope probe, connect it to the ground terminal of the amp to make sure that the scope has a good reference and do this again. The short ground eliminates errors due to long ground leads. Check the ground of the probe ground lead by making sure that you read ~0 ohms from the ground clip to the ground terminal on the scope.

 

[bigpun4fubu]

first photo is probe grounded to neg terminal on amp and probe at B+ 2nd photo is probe on positive wire of power supply and grounded to neg wire to show my power going in is very clean

 

[Perry Babin]

Do you have a relatively large capacitor (2200uf or greater) that you can connect across the B+ and ground terminals to see if helps?

 

[bigpun4fubu]

with 4700uf capacitor across B+ and ground but amp still squeals

 

[Perry Babin]

You haven't given any scope settings and in the last post didn't say where the probe was so I can't offer any suggestions.