Amplifier Repair help needed for a G&S Designs C4000

[BIG4REST]

I am searching for schematics or any information for a G&S Designs C4000.
It powers on but no sound.
I had it pushing 1- Kicker 18" cvr at 8ohms bridged in my daily driver with no problem for years.
I installed it in my project cruiser car that I am working on, I had it running 1 Kicker 18"comp vr dual 4 at 2 ohms and it played extremely well for about 2 weeks then a resistor inside burned beyond recognition and it stopped producing sound but the led is on and the fan is on but no sound. I want to repair the amplifier, so any information given on it would be greatly appreciated. I have installed audio since I was a youth but I am very green on amplifier repair. My only experiences with repairing amps were easy fixes such as broken terminals and visually burned parts, but I would like to learn and there is no time like the present to start. Thanks

[Perry Babin]

If no one else can help, email me a few photos of the inside of the amp so I can see what you have.

babin_perry@yahoo.com

[BIG4REST]

I just sent you an email let know if the pics are clear I have new camera.

[Perry Babin]

On the BUZ71A FETs, what is the DC voltage on the three legs of the transistors. They should be all the same so you should only need to post one set of 3 voltages.


Pin 1:
Pin 2:
Pin 3:

Insert a 10 amp fuse in the B+ line to protect the FETs. I'd suggest that you clamp all transistors tightly to the heatsink before you apply power.

[tsmith1315]

Originally posted by BIG4REST
I had it running 1 Kicker 18"comp vr dual 4 at 2 ohms

With Perry's expertise, you're in good hands. He's a gem.

Sounds like you had the amp bridged mono into 2 ohms?

[BIG4REST]

I will power it up and check the voltage of the BUZ71A FETs when I get home.
Thanks again for your help.

[BIG4REST]

Originally posted by tsmith1315


With Perry's expertise, you're in good hands. He's a gem.

Sounds like you had the amp bridged mono into 2 ohms?

I feel truly honored to have his assistance. I found this forum by searching for info in the G&S C4000 but I had no idea that Perry Babin was an active member here. A couple of years ago I ordered his cd and I was very impressed the way the he explained everything.

I bought the amp from an online estate sale really cheap.
When I installed it on in the 18" Kicker 8 @ohms it really impressed and it did not even heat up.
I felt that the 8ohm Kicker did not let the amp reach its full potential.

I had 2 18"s powered by 1 Us Acoustics USX-2150 bridged @2ohm each in my cruiser.

One amp went out then I had an opportunity to see what the could G&S Design C4000@2ohm could really do and I notice huge difference. about 2 weeks later the other USX2150 shut down I had just ordered a Phoenix Gold xs2500 to see if I could repair and use lucky for me that was supposed to be broken but the fuses were just melted in the socket it just looked bad but you can't even tell that it ever had a problem. When I installed the xs2500 on the other 18" bridged @2ohms my car really ROCKED!!! I could not believe how great the bass response was. The C4000 performed flawlessly and never ran hot nor went into protection for 2 months then one day a drove the car to work it played fine on the way to work and when I drove home turned the radio on and noticed that the bass was not as loud as when I parked. When I got home I found that the C4000 was on but it was not putting out any power.

So I replaced it with a Hifonics Atlantis X American Warrior 1ohm stable which has been playing for four months @2ohms but it is not as Powerful as the G&S Designs C4000.

I am going to put one Hifonics Atlantis X (Ihave two) on 1 voice coil and 1 Atlantis X more on the other voice coil until I get this C4000 fixed.

I could not find much information on the C4000 the only thing that I could find was for a C1000 at ampguts.com :
C1000

Competition Line
2 x 50W @ 4 ohms
2 x 100W @ 2 ohms
2 x 200W @ 4 ohms bridged
Fuse: External 25A


So I am thinking that the C4000 is

C4000

Competition Line
2 x 200W @ 4 ohms
2 x 400W @ 2 ohms
1 x 800W @ 4 ohms bridged
Fuse: External 100A

[tsmith1315]

I feel truly honored to have his assistance.

Perry's very generous with assistance. He'll get my vote for the forum's Most Valuable Poster anytime someone wants to take a poll.

I am going to put one Hifonics Atlantis X (Ihave two) on 1 voice coil and 1 Atlantis X more on the other voice coil until I get this C4000 fixed.

Be careful. Chances are, the low impedance load is what caused the problem.

I'm not familiar with this generation of G&S, but slightly earlier ones were private label PPI amps and not rated for less than 2 ohms stereo/4 ohms bridged. Given the spec's you quoted, it doesn't look like the C-series are stable at 2 ohms mono.

I'll look around to see if i have any spec's on this model.

[BIG4REST]

Originally posted by BIG4REST
I will power it up and check the voltage of the BUZ71A FETs when I get home.
Thanks again for your help.

When I powered the amp up, the power draw seems to fluctuate. The measurements were taken on pins 1 & 2 with the DMM on DCV (set to 20) and on pin 3 were taken on DCV (set to 2000 m). The 1 pins on all seem to fluctuate between about 1.71 to 000, 2 pins from about 13 to 9.73 and 3 pins form about 012 to 000.

Left side

Highest to Lowest

1.71 to 000
13.43 to 9.75
011 to 000

1.71 000
13.44 9.75
011 000

1.71 000
13.48 9.75
011 000

1.71 000
13.49 9.75
011 000

1.71 000
13.44 9.75
011 000

1.71 000
13.48 9.75
011 000

1.71 000
13.44 9.75
011 000

1.71 000
13.48 9.75
011 000


right side

1.71 000
13.44 9.78
013 000

1.71 000
13.53 9.75
011 000

1.71 000
13.44 9.65
012 000

1.71 000
13.48 9.45
012 000

1.71 000
13.52 9.71
013 000

1.71 000
13.51 9.51
013 000

1.71 000
13.56 9.71
013 000

1.71 000
13.56 9.42
013 000

[Perry Babin]

It sounds like the amp is repeatedly going into protection or the power supply can't produce enough current. What are you using as a DC power supply?

Have you checked all of the output transistors to confirm that none are shorted?

With your meter set to DC volts and the black probe on one of the non-bridging speaker terminals, do you see any DC on either channel when the amp tries to power up?

When you replaced the resistor, how did you know the correct value?