Starsound d2500 power supply problem

[shanecapetown]

Hi guys im currently busy doing a power supply repair on a starsound d2500 2 channel amp i replaced the tl494 ic took out buffer transistor and fitted bd 139 and bd 140. Without power supply fets the drive looks good nice and square but when i fit fets it changes drasticly I'll post pics of the drive later. It has in 47ohm resistors on the gates and 220ohm pull down resistors I also removed the rectifiers to isolate power supply from output section the power supply fets are Irfz44n

 

[Perry Babin]

Since you didn't say that the FETs were heating or that the amp was drawing excessive current, the supply is likely regulated and is pulling back the duty cycle as the target rail voltage is reached.

 

[shanecapetown]

Hi Perry it doesnt heat up but what happens is when i turn on the amp the green light comes in very slow and when the amp plays it dies down and struggles to get back on. I have to turn volume down for the amp to recover thats why i decided to re do power supply

 

[shanecapetown]

How do i know if the power supply is regulated or not

 

[Perry Babin]

Post a photo of the waveform that you think is not as it should be.

 

[shanecapetown]

Ok I will do so later

 

[shanecapetown]

This is the drain of power supply fets wave

 

[Perry Babin]

The drain isn't really significant. You need to look at the gate.

 

[shanecapetown]

Hi Perry the amp is good now it has a regulated power supply. When under load the wave looks much better and duty cycle changes as the load changes. Amp plays very nice for a 2 channel amp it's playing 2 12 inch subs of 1300rms each

 

[Perry Babin]

You can also reduce the 12v supply voltage to force the duty cycle to increase.

 

[shanecapetown]

Ok Perry that makes sense yes thank u