Cerwin Vega Vega 3204

[caraudioguy2100]

This amp isn’t producing any positive regulated voltage.

I removed the opamps since 1 of them was defective and still couldn’t get the +15 volts .

All opamps for this amp still have voltage on all pads even after they have been removed from the board .

I removed the regulator also and all 3 pads for the regulated have voltage on them .

Any ideas ?

 

[Perry Babin]

Do you have any DC voltage on the RCA shields or on the non-bridging speaker terminals?

 

[caraudioguy2100]

I have voltage on both .

I have 2 volts on rca shields and on non bridging speaker terminals

 

[Perry Babin]

OK. Ground the non-bridging terminals and post the DC voltage on all terminals of one op-amp and the all terminals of both regulators.

In the future, don't just say that you have voltage on a point without posting the voltage that is on those points.

 

[caraudioguy2100]

NE5532
Pin 1:0.00
Pin 2:0.00
Pin 3:0.00
Pin 4:-14.72
Pin 5:0.00
Pin 6:0.00
Pin 7:0.00
Pin 8:14.75


Q20 2N6488:

Base:15.15
Collector:30.21
Emitter:14.76

Q21 2N6491

Base:-15.23
Collector:-30.24
Emitter:-14.78

This is with the non bridging speaker terminal grounded

 

[Perry Babin]

What's the problem? All of that looks OK.

 

[caraudioguy2100]

If I take the ground off the non bridging speaker terminal I lose the +15 volts on the opamps

 

[Perry Babin]

Do you only lose the +15v on the op-amps?

What other voltages change compared to the voltages posted on #5?

What happens if you plug in a signal source with a grounded shield, instead of grounding the speaker terminals?

 

[caraudioguy2100]

If I plug in the signal source I get the 15 volts on the opamps .

Wondering in these amps are the regulators supposed to get to hot to touch ?

And I guess I have to use the non bridging speaker terminals in This amp to get the correct readings and not use main ground when testing the regulated voltages

 

[Perry Babin]

What other voltages change compared to the voltages posted on #5?

 

[caraudioguy2100]

Nothing has changed .

I was using amps ground terminal as ground reference at first so I had 2 volts on pins 1,2,3,5,6,7 of the opamps .

If I use the secondary ground all voltages are correct and pins 1,2,3,5,6,7 remain at 0.00 volts

 

[Perry Babin]

It's normal for regulators to get hot.

Some amps have an isolated secondary which prevents measuring voltage using the primary ground.

From the information that you've provided, I don't know why the +15v would be the only missing voltage when measuring the voltage using the primary ground.

 

[caraudioguy2100]

Back to this amp once again .

I replaced the positive regulator and an opamp .

Now this amp lokes to burn up the transistor and resistor connected to pin 8,11,12 of the 494 It’s burnt up twice now


Any ideas why this keeps happening

 

[caraudioguy2100]

Never mind I figured out why it keeps burning

 

[caraudioguy2100]

Ok got a question .

The power light on this amp consists of 5 light bulbs the originals looked like incandescent light bulbs . They were all burnt out .

I swapped them over to leds and now get the transistor that controls the 13 volts to pin 8,11,12 of the 494 to burn and blow apart .

Could switching the incandescent bulbs over to leds cause this issue ?

 

[Perry Babin]

Sure if you didn't include a current limiting resistor.