Sunday, 27 November 2016

Mini Oscilloscope

Bought this mini oscilloscope as a kit on eBay (from China as usual) for £20. The main board with the surface mount components was already completed, but the electrolytic capacitors, an inductor, diode and all the switches had to be soldered in along with the display. There is no case as such, but clever use of 2 extra pieces of pre-cut PCB and 4 stand-off fixings make for a nicely finished unit. I might make sides for it out of 3mm foam board if the notion takes me.

When I initially switched it on, nothing much happened except the backlight was on. Checking the troubleshooting guide helped and it turned out that the potentiometer for adjusting the LCD contrast needed a bit of working up and down to clean its track.

The 'scope can measure up to 2 MHz which is fine for my needs and has sample and hold and a frequency meter function. I tested it with the composite video signal from my Arduino TV-Out board and got a nice sync waveform at the right frequency.

More information at -

Friday, 25 November 2016

Retro CCTV monitor

This is the second of these little black and white televisions I've picked up. I think my wife got this one in a charity shop in Portaferry (for £3 if I remember right). They run on 12 volts or a load of batteries and have a radio as well as TV.

Anyway, a bit of Internet research revealed that all of the RF side of TV things is handled by a single chip and the composite video is dealt with by old-school transistors. This made it easy enough to cut into the video circuit at the right point and hook it up to the DVD player and we have a retro composite monitor.

The radio section was on its own board which I removed along with the speaker, front panel switches and so on. Some plastic card to fill the gaps, epoxy and satin black paint gave it a bit of 80s class! I also added a power LED to the front and re-wired the antenna jack socket to act as the video input.

The DVD player is actually a recorder I got on Freegle because the power supply had packed in. In this case the transformer had fried, maybe due to a shorted 'bad cap', so I replaced the whole power board with a similar one from another broken DVD player. A bit of drilling and soldering and it is working like new. It would make a great CCTV security recorder.