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brandes.cm 22nd September 2012 10:42 PM

Hifonics XX Hercules
 
Amp powers up fine and idles with D6 removed, that feeds the protection circuit on the p.s. driver board. I have a 40Hz signal fed into the amp and see a 40Hz square wave on the base of the inverter/voltage amplifier transistors(D1820_V51 driver board). The collector is sitting at rail. Those parts have been replaced along with the 470 ohm resistors that were out of tolerance.

I'm missing the high frequency carrier?

Perry Babin 23rd September 2012 08:02 PM

Did you check the 1D and 2D transistors to confirm that none were leaking and that all had 2 good junctions?

Don't forget to check ALL of the gate drive signals. These amps will operate even when some of the outputs aren't being driven. This will lead to premature failure of the outputs that are being driven.

brandes.cm 24th September 2012 12:45 PM

All transistors have been check and replaced.

I see gate drive of 40hz which is exactly what my input signal is. Is that correct?

Perry Babin 24th September 2012 01:05 PM

When the class D stage isn't oscillating, you will see the audio drive frequency as a square wave on the output transistors. I don't know what D6 does in that amp. You may have to reinstall it and disable the protection circuit in another way to see if it will try to oscillate. If you see excessive DC or excessive current draw, it will show you what type of fault you have and make it easier to troubleshoot.

brandes.cm 26th September 2012 01:24 AM

Reference the aq2200 schematic, pwm section IC2 pin 1 is sitting at 7 volts. I lifted D206 (upper right corner) Pin 1 stayed at 7 volts. I then lifted D9(attached to pin 1). The supply will operate and no excessive current draw, but I have no oscillation on the output.

Is there a mute circuit in this amp? It's like the American Bass XD series.

Perry Babin 26th September 2012 02:18 AM

Post the DC voltage on all 8 pins of IC2.

brandes.cm 27th September 2012 12:13 PM

Pin 3 is high on IC2, which indicates an over-current issue, but I check the readings on U1 of the driver board and those don't indicate one.

IC2
1) 12.991
2) 2.488
3) 11.8
4) 0
5) 1.068
6) 3.56
7) 0.172
8) 13.0

U1 (LM293)Driver board measurements reference -rail
1) 2.08
2) 1.342
3) 1.489
4) 0
5) 7.67
6) 1.428
7) 1.342
8) 15.69

Perry Babin 27th September 2012 12:20 PM

Is D29B omitted in this amp?

Is D13 leaky or shorted?

brandes.cm 27th September 2012 12:40 PM

D29B is not populated.

D13, I don't see it?

Perry Babin 27th September 2012 06:58 PM

My mistake. D11.


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