Hi, just ordered a DSO203, to work on solid state pinball machines. The processor technology is limited to 80’s Motorola 6800 series, running at or below 2MHZ.
I’m hoping the bandwidth of the scope is enough to be useful for this technology.
I couldn’t find anything stating the actual speed of the digital inputs, and I’m not even sure if the scope comes with digital leads.
Mostly, I just need to see activity on lines, and to be able to tell a high from a low, and observe any noise that might be on the power lines, etc.
Voltages used in a pinball machine of that era, are +5 +12 +28 -100 +100. I’m hoping that the probes in 10x mode will be able to handle +/- 400v. Is this assumption correct?
Can the digital inputs be used for triggering the scope? Are the digital inputs compatible with TTL level signals. I read that 3.3v was max, but I’m hoping that they’d be ok on 5v also.
Basic operation will be fine for viewing 2MHz waveforms pretty well using the analog channels.
You have to be a bit more careful with the digital channels as most models came with ESD protection diodes on the two digital channels that had fairly large capacitance (100pF) and combined with the series protection resistor (11K). This was certainly the case with 2.6 and 2.70 hardware. The effect of the protection is to skew the digital channels by about 1uSec with respect to the analogue plus makes them limit the frequency of the waveforms to about 1MHz. This is a bit stupid given that the channels can be fast sampled. Myself and others faced with this, have modified the circuit to avoid this limitation. Some remove the diode completely and live with less protection for these inputs. I chose to replace it with a USB 3.0 protection diode device which does the same job and has less than 1pF of capacitance so eliminates the skew and allows fast digital signals to be monitored with those channels. You need to be OK with fairly fine soldering to do the swap. There is a 2.72 version of the hardware out now and I don’t know whether that is different and improved in this area.
You can trigger from the digital inputs and because of the series resistor and some internal chip protection diodes it is actually safe to use them with TTL levels.
For higher voltages you need to be aware that there are two types of cases for the DSO203; plastic and aluminium. If you have the metal one then the case is connected to the ground and so there is additional danger of shock when working with higher voltages.
