Newly assemble pl14 rev G bias trimmers do not work correctly

[CrazyIvan]

Hello, I recently added the DC protection, then new power caps from WO. I just assembled the pl14 rev G board. Started on a DBT no issues. went to adjust bias and my DMM readings are -.019 DC on both sides. Bias trimmers turned full CCW to start. Turning CW has no effect on the DMM. I am using board test points and white and red speaker outputs as test points. If I read between white and black or white and red I get .003 VDC. It doesn't seem normal to not get any bias adjustment. Any help is appreciated.

 

[George S.]

Make sure the storage cap polarity is correct and you left the correct components off the control board for your quasi complement or full complement back wall.
If all is correct then post many good hi resolution photos.

 

[George S.]

Also check your rail voltages. With meter set to VDC, connect your negative lead to the copper bar. Touch positive lead to the other upper storage cap screw with the wired connection, should be around +80 VDC on a 400, +100 VDC on a 700. Now touch that same positive lead to the lower cap screw with the wired connection, -80 VDC, or -100 VDC depending on amp model.

 

[CrazyIvan]

I left the correct components off for full comp. I will go check voltage as you suggest, The voltage test points on the board read the correct -/+ 15 VDC, I will get photos soon.

 

[Gepetto]

Did you put your rail fuses in?

 

[WOPL Sniffer]

I left the correct components off for full comp.

huh?

 

[WOPL Sniffer]

So the "Incorrect" components are still there???


HUH?

 

[CrazyIvan]

Votages are -/+ 82.3 DC on power caps

 

[laatsch55]

Hello, I recently added the DC protection, then new power caps from WO. I just assembled the pl14 rev G board. Started on a DBT no issues. went to adjust bias and my DMM readings are -.019 DC on both sides. Bias trimmers turned full CCW to start. Turning CW has no effect on the DMM. I am using board test points and white and red speaker outputs as test points. If I read between white and black or white and red I get .003 VDC. It doesn't seem normal to not get any bias adjustment. Any help is appreciated.

Just for shits and giggles, try the stock bias test point, each side of the 10 ohm resistor on the back wall....there are 4 of them, one for each column of outputs. The ones you are concerned about are the column closest to the transformer and the 3rd from the transformer.

 

[laatsch55]

Dig the PS cap hold down bushings. Is the PS cap polarity correct, I see a + where it shouldn't be if that + is attributable to the closest post...

 

[Gepetto]

Votages are -/+ 82.3 DC on power caps View attachment 66507 View attachment 66508 View attachment 66509 View attachment 66510 View attachment 66511

Your wiring in the first picture surrounding the input copper plate is wrong. The white wire you have going from the bulk cap bus bar should go to PAD5L. There should be only the black wires soldered into that copper plate, not those 2 white wires and ditch that piece of random bus wire.

 

[CrazyIvan]

Did you put your rail fuses in?

I did not take any fuses out, Did I miss something about these?

 

[Gepetto]

Like this

 

[Gepetto]

And this...

 

[WOPL Sniffer]

Is that a cap in backwards on the DCP?

 

[Gepetto]

Dig the PS cap hold down bushings. Is the PS cap polarity correct, I see a + where it shouldn't be if that + is attributable to the closest post...

Those bushings are the standard White Oak Audio offering for the old 4 fin amps Lee. Saves drilling any holes in the chassis.

 

[laatsch55]

The one in the bottom right corner?

 

[laatsch55]

Those bushings are the standard White Oak Audio offering Lee. Saves drilling any holes in the chassis.

Is that the problem when we had our conversation about the heatshrink?

 

[Gepetto]

Did you put your rail fuses in?

 

[CrazyIvan]

Sorry to sound dumb, are the rail fuses the screw in fuses on the back? I never removed those. The amp was working after the DC and cap install. Does the copper bus bar between the large caps connect the caps + on bottom cap to - on top cap? I replaced the new ones the same direction the old ones came out. I did cut off the other white wire and remove from PAD5R. See pics, still -.019 on the test points. No trimmer adjustment.