Hifonics Goliath G5000D

[Bertje]

Some problems with this huge amp, Hifo GX5000d.

I got this amp defect to repair. All smps mosfets IRFP1405 20x are replaced, and one side of the output mosfets (12x IRFP350LC). Other 12 MOSFETS were OK (measured).

Now, amplifier power supply is normal working @ +200V
Low voltage supply -12/+12V = OK on the opamps.
After startup idle current is 3,5A, and not in protection, speaker relais are activated. Dummyload 4 ohms connected. Seems normal. No noise from smps.

But... no output on the speakerterminals, when connecting 50Hz 4V on the RCA's inputs.

I didn't get the bassremote with it, but I think it should work without.
gain, filter, settings etc. are dubble-checked.
Why...??

[Perry Babin]

If it has a master/slave switch, is is set to master?

Have you tried following the signal through the op-amps? Pins 1 and 7 should have signal.

[Bertje]

On both questions yes, switch is on "master".
Signal followed through 11 opamps, IC109 (TL074) has no signal on. Maybe phaseshift opamp?
Gainstage is working OK.
Rob.

[Perry Babin]

There's a muting transistor that sometimes fails. It's generally just behind the audio driver board (the side nearest the inductors). It's likely marked D1302. If I'm not mistaken, there's an A1266 transistor that is also part of the muting circuit and it fails. I think it's nearer the power supply.

[Bertje]

OK thanx!
Rob.

[Bertje]

I have a schematic diagram which is nealerly the same of this Hifo. There are signals "SD" called. As inputs on the driverboard as SD1 and SD2. Do you know what this SD mean? Select device..?
Rob.

[Perry Babin]

ShutDown?

How did you get the schematic. They're very difficult to find.

[Bertje]

Schematic is from another brand, it is on a few details the same as the Hifo.

Still working on it, i think there something wrong with one of the 4 driver IC's. It's unknown type, maybe IRS20124s, 14soic.
On pin 1 there is the PWM signal, but at the second right it is lower in amplitude. On the other three it is exactly the same.



Is it save to disconnect the half of the amplfier to select the good/bad side? There are two amps in parallel.

Rob.

[Perry Babin]

The driver ICs fail when the outputs fail. Either the IR21844S or the IRS21844S will work as a replacement.

What do you mean by 'disconnect the half of the amplifier to select the good/bad side'?

[Bertje]

In this amplifier there are two separate amps in parallel, which are connected just after speakerrelais.
So maybe one amp is OK, the other one fails.
But all outputs from the driverboard are suspicious. If I disconnect all stuff after the driverboard I can check it, right? Or is there a better way to check it? There are 25 mosfet-clamps and it is a lot of work to remove the PCB from the case. And a risk for damaging the new mosfets...

I contacted the German distributor for a complete driverboard.
Thanks again Perry.
Rob.