Soundstream Rubicon 1.2500 in protect

[bigpun4fubu]

yes it was on master and yes i have a scope

 

[Perry Babin]

After pin 6 on the driver board drops to near 0v, do you see rail to rail oscillation on the output transistors? The oscillation will be on leg 3 of half of them and leg 2 of the other half. You may have to drive an audio signal into it to make it oscillate.

Set the scope to 5us and 50v/div. You may have to adjust the trigger level to get it to lock on the waveform.

If you do see oscillation, do you have audio on pin 1 of the audio driver board?

 

[bigpun4fubu]

not getting any oscillation on any legs of output transistors or on pin 1 of driver board, driving input with 41hz tone

 

[Perry Babin]

Pin 1 should have normal audio.

Do you have ± regulated voltage on the power supply pins of the op-amps?

 

[bigpun4fubu]

which pins are power supply pins on op-amps?

 

[Perry Babin]

For an 8-pin op-amp, it's pins 4 and 8. 4 should have negative voltage and 8 should have positive voltage (approximately ±15v).

 

[bigpun4fubu]

i get -13v on pin 4 and -3.5 v on pin 8 of each op-amp

 

[Perry Babin]

It appears that the +15v regulator is defective. You'll have to determine what's being used for regulation. I don't have any information on this amp. If you can't find the regulator, post a photo of the entire board.

 

[bigpun4fubu]

j13 7815a and j14 7915A are 15v regulators

 

[Perry Babin]

Is the 7815 producing output?

Does it have input voltage?

 

[bigpun4fubu]

26v input neg probe on gnd terminal and 3.5v on output leg

 

[Perry Babin]

It could be that it's overloaded or is defective. Do you have a replacement?

 

[bigpun4fubu]

all i have on hand is a 7812 +12v regulator

 

[Perry Babin]

That should work for testing.

 

[bigpun4fubu]

replaced with 12v regulator , amp produces audio now

 

[bigpun4fubu]

what else should i check?

 

[Perry Babin]

You need to get the correct voltage to the op-amps before you can do anything else.

 

[bigpun4fubu]

ok