1202 ALARM

Thanks to Noel on Freegle, I have a bunch of retro 8-bit computers to play with and repair if necessary. Some cool accessories as well. 

I have a bunch of these little motors recovered from broken printers. They have a neat feedback system built onto the back using a slotted infrared sensor and an encoding wheel. All that needs to be added is a 74LS14 (or equivalent) Schmitt trigger to clean up the pulses coming from the infrared sensor. I modified the motor spindle to take the smallest Lego Technic gear and built a little test rig with a linear actuator type arrangement. The motors can be glued upside-down to a 4x2 stud Lego plate and occupy roughly the same space as a classic Lego Technic 4.5 volt motor. VIDEO -  Lego Robotics Test Rig The motor is driven by a L293NE H-bridge IC with another of the Schmitt inverters used to reduce pin count to just 2 - MotorDirection and MotorSpeed. The code uses an interrupt to count the incoming pulses on a pin and also detects a stall situation by checking if the pulse count has stopped when the motor is supposed to be running. TEST CODE // Lego Robotics Test 002 // G...

A kind Freegle user called Niamh (who owns a lovely bicycle) gave me this awesome retro Pioneer stereo system (YouTube video below).  Pioneer Stereo System The CD tray was a bit temperamental and one of the speakers might have a damaged wire, but nothing too serious and the unit was quickly back in action. I only ever came across Pioneer systems in classic cars so was keen to find out how this one performed. I hooked the stereo up to a heavy pair of speakers I got from Will on Freegle a few weeks ago and have been blown away by the sound quality. Real depth and bass. The tape mechanism and big tilt display are just things of beauty, I think I'm in love!

I was given another Acer C720 Chromebook recently and after taking the back off and removing the write-protect screw I flashed the firmware and installed GalliumOS as I did 2 years ago with the white one. Installation wasn't as slick as last time and I'm leaving the original 16Gb SSD in this one and using Google Drive for cloud storage. It seems to be working well so far.  I gave away my old HP Pavilion G6 ( laptop upgrade ) to a guy starting an OU course now that I have this laptop as well as the updated Intel-based Dell for the workshop. I also repaired this Aiwa Walkman for the lady who gave me the Acer C720. A bad synthetic drive belt was the problem, but this was fixed with a rubber belt cannibalized from an old answering machine. The synthetic belts rot away to a sticky goo that is a pain to clean off even with cellulose thinners. This needs some Wham or Duran Duran! 

A spudger (apparently) is a plastic device for prising open the cases of electronic items to get into them to repair them. You can use a flat-bladed screwdriver, but will probably crack or score the case unless you are both lucky and careful.  I never throw out used toothbrushes because they are invaluable for cleaning and degreasing engine parts (EGR valve on a Skoda Fabia being a personal favourite!). It occurred to me that they would make good spudgers with a bit of, well whittling I'd guess you'd call it. If I'm honest, the inspiration was the classic jailhouse shank actually.  Get your Stanley knife and instead of using it for a thrill-seeker liquor store hold up (putting you in the aforementioned jailhouse), whittle the tops of a couple of old toothbrushes into fine spade ends. Ideal for opening radios, DVD players and especially tablet computers. Free and greener than just chucking them away.

Another damaged portable DVD player I got from a kind lady on Freegle. She said it had been dropped and wouldn't play discs anymore. The unit powered up okay and as luck would have it, can read DVD and DivX files from a USB flash drive. A bit of testing revealed that the main turntable motor was only getting 0.5 volts instead of 6 volts and the drive transistor was probably blown. My guess is that when the unit was dropped something jammed the spindle and the stall current blew the transistor.  Anyway, my eyesight isn't up to even trying to replace a surface mount transistor so I thought, why not gut the DVD parts out of this thing and just keep it as a digital player.  And below you can see Chun Yu Fat in the classic action film 'Hardboiled'  playing from DVD files copied on to a USB flash drive. A 32Gb flash drive will hold around 45 DivX film files, plenty of choice.

Upcycled VFD Display Counter Test (Arduino) (YouTube video)  All parts are recycled or recovered from obsolete electronics, with the exception of the Arduino board.  The VFD is being driven by 2 ULN2308 transistor arrays via 10K pull-up resistors to 12volts. There are a total of 16 lines, 6 for digits and 10 for segments. Normally the VFD elements are held high (ON) , but switching a ULN2308 transistor ON pulls the line to GND and turns the VFD segment (or digit) OFF, so inverted logic.  The 2volts for the VFD filament is coming from the Arduino 5volt line via a 10R resistor. The code is based on the Arduino SevenSeg library but I will be writing my own code with interrupt-driven multiplexing for the VFD digits.

We recently upgraded to a new (to us) Nissan Leaf after over 4 years of successful and ridiculously cheap motoring in our first one. The second generation Leaf uses a Type 2 AC connector at the car end whereas the first generation used Type 1, which is now basically obsolete. New cables are £100+ so I decided to convert our existing cable instead. I had bought this from a mate for £50 because at the time Nissan didn't actually supply a charging cable, expecting home and street chargers to have a tethered cable. Some do, most don't. Anyway, when we traded our old Leaf in, I kept the cable. The dismantled Type 1 connector is shown above, ready for sale as spares on eBay to recoup some of the cost of the upgrade.  A new Type 2 plug cost £35 delivered via AliExpress and arrived in about 10 days. It was complete with the necessary 220ohm resistor which is connected between the PP pin and the PE earth pin to tell the car the plug is in and to draw up to 22kw from the char...

I took a punt on another retro portable television on eBay which was listed as non-working due to a missing volume knob. It was a Sony which I figured would be built to last and getting it including delivery for £20 I couldn't really go wrong.  It turned out the television works perfectly and I found a matching volume knob in the spares bin (probably from some other piece of Sony kit I dismantled), so a result. The case has a little damage and the tuning knob isn't working properly, but from the photo you can see a signal coming in via my old Acorn Amega RF modulator. And here's a Zoom call on it!! 

I recently had a clear out and chucked away some old PCBs from set-top boxes which had vacuum fluorescent displays (VFD) in them. Like many others, I like the retro look of these displays, so removed them before the boards were scrapped.  Having to take a couple of days in bed this week due to (finally) catching Covid-19, I watched a few YouTube videos on how these things work. It turns out it isn't that difficult to make them light up if you have 3 volts and 12 volts available. So a few initial experiments today, but a long way from anything useful for now. Bulldog clips can be really useful for all sports of things! 

The first donated 4K LCD television, a nice Samsung. Unfortunately only suitable for parts because of a cracked screen.  I'll get the power board and backlight strips out and the speakers sound a lot better than in the cheap units. 

I've been trying different component values for the composite video input on the repaired National Commando 505 television. I soldered a screened cable into the entry point to the video circuit by taking R141 (47K) in the schematic off-board. Than I tried different input capacitors and the infamous 75R resistor (which seems to kill the signal). This is digital television coming off a Freeview box.  The mag-mount aerial is handy. I need to work out how to patch up the case and whether or not to spray paint it. I could be boring and go matt black or be radical and go bright red.

A non-working one of these came up for under £20 (delivered) on eBay and I figured it would be good craic seeing if I could fix it and add a composite video input. It's a slightly different model (on the right) with a toggle power switch instead of rotary, but apart from that looks identical. I found a brilliant video on YouTube detailing how to add a composite video input to a 1977 Panasonic television which turned out to have a very similar circuit. UPDATE (13/02/22) - All that was needed to get this going again was to replace a fuse on the main board. The problem was that someone had soldered a replacement fuse into the holder at some point and it wasn't rated highly enough. I sorted out the holder and put a 1.6A fuse in and off it went.  I removed the UHF module and battery wiring and started adding a composite video input to this one. Above is an initial test using a signal from my trusty (repaired!) DVD recorder, but some tweaking is st...

Just messing about with the big Dell monitor and a Linx Windows 10 tablet Mike kindly gave me. The screen has a problem with a black bar down the centre which is physical and probably terminal, but it has a micro HDMI output so can drive a monitor. I'm going to get the screen out of the tablet at the weekend and get a part number and a good look at what has gone wrong with it, but the tablet could still be useful as a computer even with no screen! UPDATE!! 27/02/22 I passed this monitor on to Steve from Freegle/Freecycle this morning.  Unfortunately I managed to drop the stand which was glass and shattered, but the monitor will most likely be wall-mounted so not a huge problem. If it fails again it needs a STPS60170CT high specification diode costing about £5.

I got this monitor on Freegle from Noel who has kindly given me a lot of stuff over the last few years. This model is from 2008 and uses a cold cathode backlight and although heavier on electricity, they are more reliable than the later LED backlit models. The power board was dead and a bit of research online revealed a known fault which had killed hundreds of these monitors, an under specification diode which overheats and goes short circuit after 4 to 5 years. The monitor was a beast to dismantle and the power board was clearly never meant to be repaired, with heatsinks that had to be unsoldered and removed to get at the failed part. Repaired it was though, using a higher specification diode salvaged from a junk power supply. Resolution is 2560 x 1600 (roughly 2K) and the picture is exceptionally sharp with vibrant colours and smooth motion. I'm tempted to leave the monitor naked, but the inverter has high voltages so that's unsafe. I might cut a large...

National Commando 505 circa 1975, £30 on eBay. When I was growing up in Bangor there was one of these for sale in the window of Dennis Brown's electrical shop. It cost a fortune, but looked incredibly cool with the military styling and top handle. I've been tracking these on eBay for over 5 years until I could get a good one at a reasonable price. Analogue TV signal provided by the modulator from a broken Acorn Amiga RF adaptor. Runs at 12 volts on UHF channel 3. Remember when you had to tune your TV into the VCR, then Channel 5 came along and messed it up? Same idea.

Finally got round to sorting out a large number of ICs. TTL, CMOS, I2C, PIC and ATMega microcontrollers, monolithic amplifiers and a huge bunch of assorted 555 timers. Dumped a lot of obsolete ones too to make room. I found a LM1881 video sync separator I was looking for a few months ago. Coupled to a HEF4066 analogue switch a composite video signal can be manipulated. 25 years ago I built a simple video fader for film editing based round these 2 integrated circuits, but now with microcontrollers a lot more TV experiments are possible. 

So I purchased a flip-digit clock in eBay and after 3 weeks in transit from China, it arrived like this.  I asked for (and received) a full refund and as the seller didn't want a broken clock returned, I chucked it in the spares box. A few weeks later I had an hour so took the clock apart and discovered a rogue piece of plastic sprue had jammed the mechanism. Putting the 20 or so loose numbers back in place was a bit fiddly, but now it's working fine and keeps excellent time. There's also a loud and satisfying click on the hour.