Building the DSO138 Oscilloscope - Pt.3

Following on from the main board build, the next thing was to perform some voltage checks. With a 9V PP3 battery powering the board, these checks were completed satisfactorily and the various supply jumpers bridged.

At this point I installed the BNC, after giving my 45W iron time to warm up. This is one of the few issues I'm going to take with this build - there is no way the recommended 20W iron would ever solder this! Even with my 45W iron, it was all but impossible to solder the body tags of the connector. I would recommend anyone else building this to file the plating off of these studs before soldering!

Main board complete

So with all the main board now done, I installed the TFT display panel, and powered it up

1st Boot splash screen

2nd Boot splash screen

 The unit goes through two different displays while initializing. It then goes to the oscilloscope display.

Initial 'scope display, before calibration

Internal Test signal display, again before calibration

 In use, it is a little quirky at first - working out how to drive the menus. Options on-screen are highlighted using the SEL button, and then changed with the + and - buttons. The OK button in normal use selects RUNNING or HOLD mode. Input signal levels and coupling are selected by the three switches on the left.

Defective display column

All in all, its a fun and quite straightforward kit to build, and fairly easy to operate. There are header pins for UART and DATA, plus the mini-USB socket, which the instructions say little about, but which are probably for flashing updated firmware, and perhaps PC display/control.

The second issue I found, and the one which for me has marred the experience, is that one column of pixels on the TFT is permanently ON. This fault is probably a failed driver transistor in the TFT controller, and so likely not repairable. I've flagged this up with the seller.  Ideally I'd like a replacement, working display, but I will see what they come back with!

Ive not tried it with any signal other than the internal test square-wave yet, but I might use it to probe the oscillator in the HV generator circuit for the Geiger counter.