Mainline - Voltage Inconsistencies [resolved]

[hpleung]

Hi,

So all of my voltages check seems about right except for this value:

"Kreg Regulator Board (both sides) 8-12V" ==> My observed value is 3.34 volts on one side and 3.41 volts on the other side.

Any hints on where I should look?

Thanks.

 

[hpleung]

attaching a pic of the board where kreg is measured.

 

[Paul Birkeland]

If all your other voltages are OK, I would run the amp for a while and see if those voltages start to rise.  3.3-3.4V is still plenty of voltage to operate.

 

[hpleung]

Hi Paul - Do you mean I should continue with the next step with Biasing or let the unit plugged in and wait until the voltage rise from 3.34 to 8v?

 

[Paul Birkeland]

Go ahead and move onto biasing.

 

[hpleung]

Biasing - I can't seem to change the bias. The voltage at terminal 20 remains at 215volts no matter how many times i turn the bias screw clockwise or anti clockwise. I tried both the bias screw at the B side as well as the A side.

 

[Paul Birkeland]

Did you fold the leads of the little blue pot over as shown in the instructions? What are the OA and OB readings on the center PC board?

 

[hpleung]

OA is 5.23 and OB is 5.55. And it looks like I did fold the lead (picture attached).

 

[hpleung]

I re did the solder at the fold just to be safe, and got same result. Which is - I still cannot change the bias which seems to be stuck around 215 volts.

I am getting 215 DC volts on both terminal 20 and 30.

 

[hpleung]

Hold on - it looks like I miss the connections at D2.

 

[hpleung]

So fixing D2, resolve the original issue:

"Kreg Regulator Board (both sides) 8-12V" ==> I now get about 9volts instead of the 3.34 volts I got earlier.

However, I am still unable to change the Bias. The voltage measurement at terminal 20 is still 215 volts.

Attached picture of my board.

 

[hpleung]

Nevermind - I can actually change the Bias. I just had to turn a lot of rotations - I did not realize we had to turn a lot.

Thanks.