PPI PC 21400

[Perry Babin]

Are you sure that you had the meter on the channel that you were adjusting when you were measuring the DC offset voltage?

 

[mike49504]

Yes it starts at 3.57 volts and i can get it down to 3.30 volts but thats it

 

[Perry Babin]

What about the other channel?

 

[mike49504]

Starts out at 1.16 volts and i can get it to drop to 0.81 volts but thats all

 

[Perry Babin]

What is the DC voltage on the positive and negative power supply pins of the op-amps?

Place the black meter probe on one of the non-bridging speaker terminals. Place the red meter probe on the point where you need to measure the voltage.

 

[mike49504]

On the LM837N's i get the following voltages

Pin 4: 14.21

Pin 11: -14.24

 

[Perry Babin]

That's OK.

What do you get on the 3rd and 4th pins of the driver modules?

What do you get on the first and last pins of the driver modules?

Did the left channel produce clean audio?

 

[mike49504]

Right Channel

Pin 1:62.4
Pin 2:0
Pin 3: 0
Pin 4:0.0.42

Left Channel

Pin 1:61.5
Pin 2:0
Pin 3:0
Pin 4:0

Left Channel produces clean audio


Right channel distorted audio and still have 3.86 volts on it

 

[Perry Babin]

The last pin, not pin 2.

 

[mike49504]

Last Pin right channel

-62.2

Last pin left channel

-62.2

 

[Perry Babin]

http://www.bcae1.com/temp/ppidriverboardresistoroverlay01.swf

With no power applied. Measure the resistance as shown in the following image:
http://www.bcae1.com/temp/ppidriverboardresistoroverlay01.swf

Resistance A?

Resistance B?

 

[mike49504]

On 1 driver board

Resistance A:101.2 ohms

Resistance B:100.6 ohms


Other driverboard

Resistance A:100.1 ohms

Resistance B:2.055K ohms

 

[Perry Babin]

2k is defective. Solder a 100 ohm resistor as shown in the image so that both read 100 ohms and try it again.

 

[mike49504]

Ok soldered the 100 ohm resistor as shown in the pic..

Now do i power it up and check to see if there is voltage on the right channel??

Resistance A: 100.1 ohms

Resistance B: 95.2 ohms

 

[Perry Babin]

Yes.

If it works, you need to remove the transistor over the resistor that's printed on the board and cut the rest of the resistor through so that it doesn't cause any problems. You'll need to do this with a razor knife and you'll need to be very careful so that you don't crack the board.

 

[mike49504]

The voltage does drop but i still have 1.50 volts after i added the resistor and messing with the DC offset pot doesnt make any changes

 

[Perry Babin]

Does it produce audio?

 

[mike49504]

Yes it produces audio but when i connect a speaker to that channel the current draw still goes up a lil like 1-2 amps and the transformer squeals

 

[Perry Babin]

I wouldn't be concerned about the transformer noise if the noise isn't getting through to the speaker outputs.

So... at this point, the only fault remaining is that the DC offset cannot be set to less than 0.05v DC in either channel?

 

[mike49504]

yes