It’s important to talk about failure as we can often learn from it and this brief write-up is all about something which left the workshop, ready for recycling. I made it go bang, sadly.
Remember TVs before the networks ‘went digital’? They had analogue tuners built-in, which received the signals. With so many old TVs out there, manufacturers sold digital set-top boxes, which allowed an older TV to work with the new digital TV stations from about 2007. Since then, manufacturers include a digital receiver within their TVs of course and this particular device now seems a bit of a museum piece.
This SEG DVB Digital TV box had failed completely, so off with the lid. Once open, the printed circuit board (PCB) was revealed. The PCB on this device was made in two halves; one for the TV reception stuff and one for the power, the conversion of mains electricity to lower DC working voltages. The power part of the board had some visible damage and it appeared that a smoothing capacitor had gone pop.
As it happened, I had a similar device on the shelf I was gradually stripping for spares and was able to quickly identify a suitable replacement. Once re-soldered in and powered-up, nothing happened!
Then I spotted an on-board fuse which had also failed, but I didn’t have one of these, so I decided to temporarily short the fuse connections to make a connection. That’s when things got smoky.
I’d missed the fact that a small transformer on the PCB had a winding short on it, which had impacted on the rest of the components. Bang.
Never mind. Digital boxes are still available online and that’s what I did, I ordered a new one.
Although I didn’t win this one, it’s important to have a go and that’s the whole point. If it’s not working to begin with, what’s the worst that can happen?
Cost of repair: A new DVB box at about £20.
Fix It Workshop 