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mbates14 17th April 2013 03:18 PM

Hifonix BRZ1200.1D issue
This one has a weird issue that I cant pin down.

It works, but it has really low volume. I have to turn the gain all the way up before it begins to beat the subs. Then when I do this, it starts clipping only at certain frequencies, and when this occures it starts cooking the sub, B+ rails drop during clipping.

Idle no clipping I have +/-65V rails. they sag to about 30v when clipping. And its burning the sub when it clips.

mbates14 17th April 2013 03:54 PM

Quick measurements gave me this:

100Hz Sinewave tone into RCAs. 0.4VAC input on RCAs.

R201 couples the pre-amp/crossover stage to the Class D driver board. the Driver board side with gain turned all the way up is 0.8VAC.

Pre-amp side of resistor is about 6.5VAC. Resistor measures fine.

is this normal? or is the class D driver bad. Both 8 pin SOIC-W ICs are scratched off. Both get really hot.

any ideas?

mbates14 17th April 2013 11:40 PM

I see......

Anyway, I figured out the 2 ICs on the driver PCB are TL072. I have an O2 audio which is a hifonix PCB and it wasnt scratched off.

Replaced them and the issue seemed to have gone away. We will see.

Perry Babin 21st April 2013 01:20 AM

When you repair these amps, replace the two 1D transistors in the center of the board, even if they're not defective. They run hot and commonly fail.

mbates14 21st April 2013 01:27 AM

Center of which board? also what package, SOT-23?

Perry Babin 21st April 2013 01:59 AM

1 Attachment(s)
See attached.

mbates14 21st April 2013 11:57 PM

Yea, I changed the 2 072s on that board. The top right one looked brown where it had gotten hot, and was getting hot. Changing those 2 op-amps improved the sound.

I didnt change those transistors yet. What is the symptom of these failed transistors?

seankane 22nd April 2013 07:30 AM

Amp stays in protect.

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