Ppi a1200

amc32 · 8th February 2010, 06:49 PM

Hi,
I am having a problem w/ a ppi a1200 amp. It looks like I have a complimentary power supply, where the fet's are working in pairs. The problem I am having is that when I install the fet's on one side of the power supply, the amp starts drawing 20 amps for a second or two then drops down to 1.5 amps. Then the fet's start to get blazing hot after just a few seconds w/o any load on them. If they are not in the other bank idles just fine w/o getting hot at all. Help would be appreciated in figuring out what is causing this problem. Thanks in advance.

Perry Babin · 8th February 2010, 07:31 PM

This is an H-bridge supply. If the transistors are only in one side, the transformer isn't being driven. If no FETs overheat when all FETs are one side OR in the other side, the drive circuit is probably OK.

Is it possible that your 12v power supply voltage is dropping significantly when the amp is only drawing 1.5 amps?

You could have a shorted transformer, inductor or something in the audio section that's causing excessive current draw.

8th February 2010, 06:49 PM	#1
amc32 diyAudio Member Join Date: Mar 2008	Ppi a1200 Hi, I am having a problem w/ a ppi a1200 amp. It looks like I have a complimentary power supply, where the fet's are working in pairs. The problem I am having is that when I install the fet's on one side of the power supply, the amp starts drawing 20 amps for a second or two then drops down to 1.5 amps. Then the fet's start to get blazing hot after just a few seconds w/o any load on them. If they are not in the other bank idles just fine w/o getting hot at all. Help would be appreciated in figuring out what is causing this problem. Thanks in advance. __________________ ...............I Hear in color.................

8th February 2010, 07:31 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	This is an H-bridge supply. If the transistors are only in one side, the transformer isn't being driven. If no FETs overheat when all FETs are one side OR in the other side, the drive circuit is probably OK. Is it possible that your 12v power supply voltage is dropping significantly when the amp is only drawing 1.5 amps? You could have a shorted transformer, inductor or something in the audio section that's causing excessive current draw. __________________ Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing

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