SKAR RP-150.4AB

imraneesa

Member
2016-04-23 12:14 pm
Hi
This amp is going into protect after playing for few seconds. This happens with or without load.

This happens only with input signal. It stays good with medium signal and no rise in current. Once you increase the input signal it pulls current and goes into protect even though there is no load.
 

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imraneesa

Member
2016-04-23 12:14 pm
If that's compressed air in the can in the photo, cool the bias transistors to see if the current draw increases.

Has the amp been working normally and just started doing this?

Are the regulated voltages about the right voltage?
When I sprayed the compressed air the current did not increase when idle but remain same. But it took longer to go into protect when I freed bias transistors. Person told he bought it new just like that. He dont have warranty. as he purchased from some third party.
 
The information seems a bit confusing. Correct me if I'm wrong.You stated that the problem was not as bad when you moved the bias transistors off of the heatsink. And also that freezing the bias transistors didn't cause a current increase.

Generally when you have a problem like this, it's a bias issue where the bias setting is too close to the threshold and a slight change in the temperature of the bias transistors or the output transistors will cause a change in current draw. That didn't happen here.

It could be a problem in the PS if the drive isn't sufficient, if the power supply is regulated.
 

imraneesa

Member
2016-04-23 12:14 pm
The information seems a bit confusing. Correct me if I'm wrong.You stated that the problem was not as bad when you moved the bias transistors off of the heatsink. And also that freezing the bias transistors didn't cause a current increase.

Generally when you have a problem like this, it's a bias issue where the bias setting is too close to the threshold and a slight change in the temperature of the bias transistors or the output transistors will cause a change in current draw. That didn't happen here.

It could be a problem in the PS if the drive isn't sufficient, if the power supply is regulated.


I did not move the bias transistors away from heatsink. I just sprayed on its legs and idle current did not change. Do you want me pull bias away from heatsink and try again.



What I observe is that when I sprayed on transistor legs song played little longer. But it was not too long to talk about.
 

imraneesa

Member
2016-04-23 12:14 pm
I took 'freed' for unclamped.

If the amp is still in the heatsink. measure across the NPN/PNP emitters of the various channels. What is the initial voltage?

Does the voltage increase as the amp shuts down (no load)?
When I am driving low frequency without load the amp remains cool. But if I drive high frequency amp pulls current and outputs getting hot and some times the current will go to idle current and it pulls again immediately. but no voltage across emitters.