Soundigital 8K

[brandes.cm]

Cap measures 1uF, marked 105 630V.

 

[Perry Babin]

If you place both probes on the same speaker terminal, do you get a perfectly clean trace that is precisely on the reference line?

If you connect a dummy load to the amp, does the current draw increase?

 

[brandes.cm]

If you place both probes on the same speaker terminal, do you get a perfectly clean trace that is precisely on the reference line?

If you connect a dummy load to the amp, does the current draw increase?

I pulled the inductors, will check them on the lcr meter at work.


If I connect a load the amp will pull 30 amps immediately upon a signal being applied.

 

[brandes.cm]

With both probes on the + speaker terminal I see this waveform.

Scope set to Add, channel 2 inverted, 50V/div, maybe 10uS/div

 

[Perry Babin]

Something is wrong. In differential mode, if you place the probes on the same point, the trace should not be deflected (should remain a straight line at the reference). It could be that the probes aren't matched well enough. Try placing them on a 12v DC source to see if they work properly. It could be a high-frequency response issue with one of the probes.

 

[brandes.cm]

Cal pot was messed up. Here is the output signal with 1khz input. Current increases until the signal starts to clip, then slowly drops.

 

[Perry Babin]

Did you find a problem with the inductors?

What was their inductance?

Does it still draw excessive current when you connect a load to it with no input signal?

 

[brandes.cm]

Did you find a problem with the inductors?

What was their inductance?

Does it still draw excessive current when you connect a load to it with no input signal?

The inductors measured 20uH I believe, don't think it was 20mH.

If I load the output with 4 ohms the clip circuit is tripped. Then I get no output.

Sent from my DROID BIONIC

 

[Perry Babin]

What happens if you power it up with the load already connected?

 

[brandes.cm]

Clip light comes on, right away.

 

[Perry Babin]

Are you sure that your supply is capable of powering this amp?

 

[brandes.cm]

Are you sure that your supply is capable of powering this amp?

30amp supply, doesn't dip while it powers up.

Maybe the clip circuit trips when it powers up initially. It has a self test on power. I'll monitor the voltage.

Sent from my DROID BIONIC

 

[brandes.cm]

I paralleled a battery with my supply, no more clip light on power up. Supply must have dipped during the amp power up test.

The signal still seems noisy, maybe these amps are this way?

 

[Perry Babin]

These and Stetsom amps are essentially the same. The Stetsom amps that I've had in the shop were all very noisy. These were the older models but I don't think that there were many improvements. If it's operating at the right frequency (likely is because it's determined by a crystal oscillator) and the output filter components are OK, I'd think that it's normal.

 

[brandes.cm]

I hooked it up to a 2 ohm sub and it did fine. I will install it in my car for a final test.

Tough to load a 8K amp with my setup.

 

[blazer40]

Did you ever land a schematic for this amp?

 

[brandes.cm]

Nope