Planet Audio VX2200D dead need Help!

[Simontempler]

Hi everyone, thanks for having me.
I am a newbie at this type of amplifier.
Nothing seems burn, what I notice was, when remote terminal have 12v there is a fan that start spin-in, other than that there is no power on the output FET's.
It uses a KA3525A to drive the switch mode power supply. I downloaded the datasheet and I am not getting the voltage reference leading me to believe I may have a bad IC. Need your opinion on this mater.
Listed below are the voltage taken from ic301 KA3525A: using 1ms/5div
01: 0v
02: 0v
03: 0v
04: 0v
05: 0v
06: 0v
07: 0v
08: 0.7v
09: 0.4v
10: 0v
11: 0v
12: 0v
13: 10v
14: 0v
15: 10v
16: 0.4v

Thanks for your assistance in this matter

[Perry Babin]

It could be a defective IC or something dragging the 5v reference down.

10v on pins 13 and 15 is also quite low. There may be another problem if your 12v power supply was at or above 12v.

[Simontempler]

Acting on your tip Perry I remove ic301 and bread boarded it to see if I can duplicate the problem and sure enough I'm only receiving 0.4v on the reference terminal.

I connected a series resistor to the terminal pin 16 on the board and the voltage drops across it was very minimal the current go through it was only 7 mA this of course without the chip installed.
I wanted to know if I had excessive current draw.

I don't have another chip so I will order some and repost when I get them.

Thanks very much.

[Simontempler]

OK fellows, I finally got the pwm ic from eBay and installed it. The amp powers up, I have rail voltage ~60v, the green power light and the protect light stays on I also notice a burn resistor of unknown value at R101 would this be the cause for the protect light to stay on? and what value is that Resistor.
Thanks for your reply.

[Perry Babin]

R101 is a 220 ohm resistor. I don't think it can cause the amp to go into protection unless possibly if the RCAs are plugged in.

This resistor generally fails when the transformers have (intermittent) shorts or when the positive speaker wire shorts to chassis ground.

This type of amp is covered on the class D - type 2 page of the tutorial. There are a lot of other common problems with these amps that need to be addressed.