Hi. I've just put together a DSO 138 kit I've had hanging around for a year or so. It is a genuine kit 04 version where you have to mount the smds.
All works fine apart from one problem with the coupling. When you switch to ac it says DC on the screen, Ground is fine.
When you switch to DC it says DC! I have blanket soldered the board. Checked all the component values, flashed the MCU 066 firmware, changed the coupling switch - still no joy! I suspect that the MCU is responsible maybe faulty??
Can anyone help with any ideas here?
Thanks Mark.
Coupling switching errors.
Re: Coupling switching errors.
The range indication circuits for a three switches are the same. To the right of R19(CPL), R22(SEN1) and R25(SEN2) there are unlabeled test points.
As you move the switches from left to right the resistance readings are approximately 1.5K, 4.1K and 3.6K.
With power on the voltages are 0V, 1.2V and 3.8V
I hope this helps.
As you move the switches from left to right the resistance readings are approximately 1.5K, 4.1K and 3.6K.
With power on the voltages are 0V, 1.2V and 3.8V
I hope this helps.