Power Up Test DSO 068

[jye1]

Here is the jpeg format

[bigxo]

Thank You Very Much for the Jpeg.
bigxo

[bigxo]

The U2 Pins are giving the following readings. SW3 Reads the following.
Pin 4 is -4.9V Pin 1 is 0
Pin 5 is 0 Pin 2 is 0
Pin 6 is -1.2V Pin 3 is 0
Pin 7 is 3.5V Pin 4 is 0
Pin 8 is 4.9V Pin 5 is 4.9V
Pin 6 is 0
Pin 7 is 2.5V
Pin 8 is 0

Is U2 Bad? Looks like Pin 7 to Pin 6 is dropping voltage but Pin 7 to Pin 5 is open?
Thanks for the Help

[bigxo]

Sorry for the screw up here is what I read.

U2 Readings Pin 4 is -4.9V, Pin 5 is 0, Pin 6 is -1.3V, Pin 7 is 3.5V, Pin 8 is 4.9V

SW3 Readings Pin 1 is 0, Pin 2 is 0, Pin 3 is 0, Pin 4 is 0, Pin 5 is 4.9V, Pin 6 is 0, Pin 7 is 2.5V, Pin 8 is 0

Is U2 bad it looks like it drops the - side Pin 6 but not the + side Pin 5????

[Jonathan]

I have used 7-zip (freebie) on Windows 10.

[bigxo]

Your Troubleshooting Guide shows a picture of readings, here is what I read. What do you think I should do next? I Still need to know about Chip LM6172 (U2) What do you suggest ??
V1 0
V2 0
V3 0
V4 You show -1.6V with SW1 on Ground I read 3.5V
V5 You show -1.6 and I show -3.4V
+5V I read 5V
-5V I read -5V
AV+ I read 4.99V
AV- I read-4.96V
VB I read .6V
VT I read 2.6V
VA I read 4.97V
VEE I read 5V
Sysclk I read 2.5V
Vbus I read 4.9V

[jye1]

Please check resistors R9, R10, and R11 for soldering and their values. Looks something wrong with these parts.

[bigxo]

Ok I first took one end of R9,R10 and R11 loose from Board and I read
R9 .997K Should be 10K
R10 3.29K Should be 3.3K
R11 468 OHM Should be 470 OHM

Now I resoldered and read across the resistors
R9 .675K
R10 3.29K
R11 418 OHM

Now I checked the resistance to test points on either side of resistors.
R9 I read between AV- and U2 Pin 6 .683K
R10 Read between R9 & R11 and TP4 3.1K
R11 Read between Grd. and R0 & R10 417 OHM

[jye1]

V4 still the same? Please also check AV+ and AV- right at the pins of U2 if you still get wrong V4.

Another try. Please disconnect R9 to see whether you can make V4 zero.

[bigxo]

OK
V4 still reads 3.5V
I unsoldered one end of R9 and V4 read -17.3mV, The other end that was still hooked to the board read -4.9V.
I Re-soldered R9 and V4 went back to 3.5V ?????