Bottlehead Forum

General Category => General Discussion => Topic started by: hpleung on December 25, 2021, 12:41:03 PM

Title: Incorrect Voltage Measurement
Post by: hpleung on December 25, 2021, 12:41:03 PM: Hi,

I clearly am getting wrong voltage for this step - "Clip the black lead of your
Digital Multi Meter to the -6.3vDC solder pad on the power supply board. Clip the red lead to
the +6.3vDC solder pad on the power supply board.".

What I read is 11.25 volts - when I should be expecting around 6.3 volt DC.

The previous 2 measurements was within range.

1. "Attach the red lead to terminal 12, and the black lead to terminal 11."

Obtained 139.5 volts (Acceptable Range was 130 to 150)

2. "Clip the black lead of your Digital Multi Meter to power transformer terminal 7. Clip the red lead of your DMM to power transformer terminal 9."

Obtained 9.52 volts (Acceptable Range was 8 to 12 volts.

Are there any pointers on where I should look? I will post a picture shortly.

Thanks.
Title: Re: Incorrect Voltage Measurement
Post by: hpleung on December 25, 2021, 12:44:58 PM: Attached pic of the board.
Title: Re: Incorrect Voltage Measurement
Post by: Paul Birkeland on December 26, 2021, 08:08:35 AM: Quote from: hpleung on December 25, 2021, 12:41:03 PM
What I read is 11.25 volts - when I should be expecting around 6.3 volt DC.
Be absolutely certain your meter is set to DC volts, not AC volts. If that is not the issue, I would unscrew the board and post some photos of the soldering on the bottom.
Title: Re: Incorrect Voltage Measurement
Post by: hpleung on December 26, 2021, 08:37:05 AM: Hi,

Still trying to find the issue. I have confirmed that between T7 and T9 is 9.5 volts.

I have also confirmed that the meter is set to DC voltage measurement.

Attached the picture from the bottom.

Thanks.
Title: Re: Incorrect Voltage Measurement
Post by: EricS on December 26, 2021, 09:29:37 AM: May or may not be related, but I see two VERY long legs poking down from the bottom of the board next to your red and black wires. Be sure they are not touching anything else below the board when it is mounted. Iâ€™ve shorted more than one component this wayâ€¦. ;D
Title: Re: Incorrect Voltage Measurement
Post by: debk on December 26, 2021, 10:35:23 AM: Don't know if it is just the picture but it looks like one of the pads are not soldered or not soldered well (top left square pad, one of the diode leads)
Title: Re: Incorrect Voltage Measurement
Post by: Paul Birkeland on December 26, 2021, 11:57:45 AM: Also be sure you have the 1085 regulator installed on that board and not an MJE5731A.
Title: Re: Incorrect Voltage Measurement
Post by: hpleung on December 26, 2021, 01:30:54 PM: Paul I think you are right. Its the wrong one installed. I need to figure out how to desolder it.

Thanks - pretty sure this is the problem.
Title: Re: Incorrect Voltage Measurement
Post by: Paul Birkeland on December 26, 2021, 01:32:37 PM: The blue spring loaded solder vacuum pump will do this job pretty well.