DS068 and switch (BOB3)

[Jonathan]

I have a working scope powered by USB.

Removed JP2 and re-installed BOB3; scope not powering up.

Voltages to BOB3 connector as follows:-

Continuity between ground and connector 2 good.

Switch not depressed
Connector1 5V
Connector3 0V (VOUT)
Connector4 0V (PWROFF)
Connector5 0.45V (PWRON)

Switch depressed
Connector1 5V
Connector3 0V
Connector4 0.12V
Connector5 0V

I can see connector 5 (schematic label PWRON) going to 0v is correct through SW4.

With JP2 closed and BOB3 removed the +ve of D3 (PBDETECT) is 4V.

With SW4 not de-pressed should POWERON be greater that 0.45V (could BOB3 Q4 be conducting when it should be off)?

I was thinking of changing BOB3 Q4 and Q5 although not easy to identify and the size makes it difficult.

Any assistance appreciated. Can I buy another BOB3?

[Jonathan]

Issue is probably that C33 is actually a 1M ohm resistor.

[jye1]

Yes C33 and C36 were mistakenly with resistors installed for some boards. More critical is C36. It has to be there to turn on the switch.

A replacement board was sent out to you a few days ago.

[Jonathan]

Thank you.

[Jonathan]

BOB 3 replaced and now all okay. Also inserted D5 and now powered from external 5V power source.

Thanks for your help.

[GTNMUDY]

I have a question for you.

With the EXt 5V power supply plugged in can you turn the unit on/off with the push button without a int battery installed?

My unit will only turn on/off with a int battery installed.

[Jonathan]

I have no battery and no charger; the switch does turn on and off the scope.

[GTNMUDY]

OK, so your using the USB to operate the scope.

I was just wondering because I can turn scope on/off with int 3.7V battery but when the charger is plugged in the scope will come on but cant turn off.

[Jonathan]

Yes using USB and external power supply. No battery or charger fitted because I never remember to charge things.