JBL GTO 1201.1 Problem

[bigpun4fubu]

When playing it hard the relay kicks off and protect light comes on and protect light is on very dimly all the time any ideas? have replaced all power mosfets and all check good

[amc32]

What is the speaker load presented on the amplifier? Do you own a scope?

[bigpun4fubu]

4 ohms yes i have a scope

[amc32]

With the amp with no speakers connected what is the dc offset voltage? Are there any irregularities on the scope in the oscilation of outputs?

[amc32]

Your 4 ohm load, is it a dummy load or speaker?

[bigpun4fubu]

its a dual 2 ohm sub wired at 4 ohms , where do i check that , im still learning

[Perry Babin]

Are you sure that the voltage at the B+ and ground terminals isn't dropping too low?

In the original post, you mentioned the protection LED twice. Was this intended or was it a typo?

Or is the protect LED always lit dimly, even before it goes into protect mode?

[bigpun4fubu]

yes dimly lit with no load

[bigpun4fubu]

it plays thru several frequencies and never drops below 13 volts til it hits 47 hz my power supply is a 30 amp continuous dc powersupply @ 13.8 v 47 hz is the only freq that makes it cut off but the protect light gets brighter as the bass hits

[Perry Babin]

With the amp on, no load, no signal, place the black probe on pin 4 of U401. Post the voltage on the other pins.

U401
Pin 1:
Pin 2:
Pin 3:
Pin 4: black probe
Pin 5:
Pin 6:
Pin 7:
Pin 8:

What is the DC voltage on pin 4 of the TL494 on the power supply board? Place the black probe on the amp's ground terminal for this.