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Coming up in Silicon Chip Subtractive Manufacturing Dr David Maddison details the history of manufacturing techniques involving devices like mills and lathes, through the early years of numerical control and onto the amazing modern CNC machines. These can create a wide array of shapes out of solid blocks of metal, timber, plastics or other materials with extreme precision and virtually no human labour. He also explains quite a few other modern subtractive manufacturing techniques that you may not be aware of. Touchscreen RCL Box This handy device fits into a compact Jiffy box and puts 43 resistance values, 19 capacitance values and 11 inductance values at your fingertips. It can even step through a range of values by itself, to make testing and prototyping really easy for you. Plus it displays the characteristic frequency of various RC, LC and RL combinations. Advertising Index Altronics...............................75-78 Ampec Technologies................. 67 Control Devices..................... OBC Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. IBC Hare & Forbes............................. 7 Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 RTL-SDR dongles with inbuilt upconverters LD Electronics......................... 111 Following on from the article in this issue, Jim Rowe examines two low-cost offthe-shelf SDRs with inbuilt upconverters. They claim to give significantly better performance than the smaller and cheaper dongles which use the “direct sampling” approach, described in this issue. LEACH PCB Assembly............... 5 Tektronics T-130 ‘Elcee’ Meter Ocean Controls........................... 8 An in-depth look at the operation and restoration of a classic piece of vintage test equipment. This was one of the devices that helped make Tektronics famous. It used some ingenious principles to give extremely accurate and stable inductance and capacitance measurements, with a very clever arrangement of thermionic valves, wafer switches and passive components. RayMing PCB & Assembly........ 10 LEDsales................................. 111 Microchip Technology.................. 9 Silicon Chip Back Issues.......... 81 Silicon Chip PDFs.................... 95 Silicon Chip Shop...........108-109 Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The June 2020 issue is due on sale in newsagents by Thursday, May 28th. Expect postal delivery of subscription copies in Australia between May 26th and June 12th. Philips TV using another HDMI cable. This was our “spare TV” and about 18 months old but with very few hours on it. All seemed well, so I turned down the volume and left it running, confident that if the fault appeared, I would hear the noise. About an hour later, I discovered that the Philips TV was completely dead, without even the standby light on. Investigations showed that the power supply was delivering all the voltages expected if the TV was in standby, but it could not be roused from that state. The circuit is basically a tuner, power supply and a megapin IC that seems to be everything else required to make a TV work. As I wasn’t watching when it died, I am not sure if there was any unusual display, but I am confident 112 Silicon Chip that the PVR ‘bricked’ the TV via the HDMI. An internet search showed several people saying that an HDMI connection had damaged their TV, but in nearly every case, there was a reply from a tech ‘guru’ telling them that they are wrong, that HDMI cannot damage your equipment. I am not so sure now. I replaced the Topfield with a Panasonic PVR, which can do a lot more, and the problems with the TV have stopped. So am I right in thinking that a faulty device with an HDMI output can damage a television? (B. T., Bonogin, Qld) • It sounds like your PVR had a fault which was not only interfering with its own operation, but was also delivering voltages to the HDMI cable outside of the normal range. These have Australia’s electronics magazine Silicon Chip Special Offer........ 35 The Loudspeaker Kit.com........... 6 Vintage Radio Repairs............ 111 Wagner Electronics................... 99 confused/damaged the TV(s) via their inputs. Probably your Kogan TV has better protection on the HDMI inputs than the older Philips TV. You probably aren’t surprised to find out that many of these internet ‘gurus’ think that they know a lot more than they actually do! Unless the connection is galvanically isolated (eg, optically or via transformers), there is always the possibility of damaging voltages travelling from one device to another. We’ve even seen a USB battery pack fail and ‘brick’ a charger. Replacing the PVR was a good idea. It may be possible to repair the old one, but probably not economically. And you risk damaging more TV inputs if you go to test it, thinking you have fixed it, and you haven’t. So we’d leave it well alone and move on. SC siliconchip.com.au