Sunday, 11 March 2018

I've been fiddling about with a 40" Samsung LCD television today. I was given this free because the power board had packed in. The previous owner had attempted a repair by replacing the 'Bad Caps' (i.e. blown electrolytic capacitors, Google that one!), but the de-soldering and soldering was a bit ropey looking so I tidied that up and replaced 2 of the capacitors myself as one didn't look right and the other was the wrong value. I managed to find a schematic diagram online for the board (Hansol SIP400B), which was helpful in identifying the capacitor values.

Anyway, I put it back in the TV and powered it up and all the voltages coming off the board are correct, but all it does is click. This is the result of a relay on the board switching the circuit from  standby to power on. The red LED on the front panel lights and the set is receiving IR signals from the remote control.

This is really frustrating, but as 95% of these boards suffer from Bad Caps, I might just buy more new ones from CPC (which should only cost about £3) and give it another go. It would be bad to lose such a nice Samsung TV, which I was going to give to the Wee Man to use with his PS4.

Saturday, 13 January 2018

Retro Keypad Find

I was having a clear out and found this homemade keypad. I built this as part of my computing project when I was training to be a teacher in 1989. I used to go up to the Maplin store in Edgeware on the tube to get parts, or Cricklewood Electronics which was like the Old Curiosity Shop. This wasn't cheap either, I had to buy about 20 of the switches with separate caps, but it looked good when it was done with the Letraset transfer letters. The keypad was wired to a Sinclair Spectrum to allow entry of Logo-ish commands to a Lego Technic robot buggy.

Happy days!

Thursday, 28 December 2017

Classical Gas

(Apologies to Mason Williams)

We switched our central heating to a gas boiler in November, which is working out really well, but the stove presented a bit of a challenge. This has been our main source of heat and hot water for over 5 years with the oil boiler acting as a back-up coming on for an hour in the morning and again in the early evening until the stove was lit and up to heat.

With the gas boiler the central heating has changed to a pressurised system which is incompatible with the stove's back boiler. The concern was in running the stove 'dry' as we like having a fire in the winter. Would the existing copper pipe overheat or worse?

The solution was to create a separate mini gravity-fed convection heating system with one radiator. Admittedly this is the highest-output radiator I could get from ScrewFix at 2.2kW which would fit the available wall space on the landing.

The plumber removed the special £600 dual-coil copper tank (groan) and moved the expansion tank in the loft as high as possible.

So far the radiator has dumped away the heat very efficiently and the upper floor in mi casa is comfortably warm when the stove is lit even when the gas boiler isn't running.

The carpet will be replaced during 2018!

Sunday, 25 June 2017

Tablet Repair Part 2

So when I was replacing the broken USB connector on the Samsung Galaxy Tab I managed to get a bit too much heat onto the main board and melted the lens of the front-facing camera. This was really stupid because I could have easily removed the camera before doing the soldering. I think the tin foil might have worked against me here.

This is the old camera module with the lens removed, it still worked, but was pretty useless. I raided the broken bits box and tried a couple of web cams from an old netbook and 'phone, but couldn't get a lens that would fit, so I just bought a new one on eBay for about £12.

I went the whole hog and bought a rubber bump case and screen protector for £10 because I liked the rugged look of the thing. The case is a nice one my wife got me for Christmas with a classic version of the periodic table on the front and a matching notebook. I stiffened the case with a piece of foam board behind the tablet for a bit more protection.

Saturday, 24 June 2017

HP Laptop Repair

A nice HP laptop I was given by another kind Freegle user which had stopped working.

It is about 4 or 5 years old and nicely specified for running Linux Mint with 4 GB of ram and a fast multi-core Intel processor running at 2.2 GHz.

The guy's kids had been using it and it was covered in colourful stickers, which was cute, but it was also full of dust, probably because the kids had been sitting on the carpet to use the computer. This is really common and you see the same with Playstations and XBox consoles because they are usually put under the television on the floor.

The computer was reporting a fan failure which a bit of research turned out to be very common for this model. The fan sounded like it was on its last legs, so a full strip down was needed, then a serious clean out to remove all the dust and finally a replacement fan off eBay for about £4. The keyboard wasn't great so I got a new one of those as well for £7, total cost of parts £11. I carefully took all the stickers off and gave the laptop a good clean and it is pretty much as new.

Now running Linux Mint 18 (obviously) like lightening.

Tablet Repair Part 1

This was one of the hardest repairs I've ever attempted. I got this lovely Samsung Galaxy Tab E (9.6-inch screen) from a kind Freegle user. It was dead, but a good look showed up that the micro USB socket was broken. I stripped the tablet down following a couple of useful YouTube videos and got the main board out.

The only way to really work with surface mount components is using an SMD re-work station, a kind of soldering iron using hot air. I don't have one of these, but I do have my trusty B&Q hot air gun for plumbing and paint stripping. This is way too big for this work, but by wrapping the circuit board in tin foil and using the gun on the lower setting I was able to get the old USB socket out. I soldered 2 wires to the power contacts and partially re-assembled the tablet. 

The tablet has intelligent charging and due to the odd connection it took about 12 hours to fully charge, but when it did the tablet booted up and I was able to do a factory reset and log in with my own Google account.

So far, so good. I bought an exact replacement USB socket on eBay for a little more than £1 and when it arrived I took the circuit board out again. Now the fun really began. After trying to solder the new socket into place with a small iron I realised this wasn't going to work and it would be back to the hot air gun and tin foil approach.

After 2 hours of messing about I finally got the new socket in place, fully soldered and connected correctly. Flux turned out to be really useful in getting this done, it helps to clean the contacts and make the solder flow. I have since found out that solder paste is what you should use when working with surface mount boards so I'm going to order some from CPC for future use.

Gazebo Repair

We have had one of those pop-up gazebos for a few years, very handy for barbecues and picnics and so on. Unfortunately, it got caught in the wind last week (my fault, it wasn't fixed down securely) and as my wife and son tried to get it popped down one of the struts snapped. There was a bit of damage to a couple of the plastic corner pieces as well.

Not too difficult a repair although I couldn't find any scrap tube with the same oval profile so I used a round piece and crushed it at the 2 ends and middle. The damaged corner pieces are okay for now, a couple of cracks, but I replaced the self-tapping screws with nuts, bolts and washers.

The repair worked out so we should get a bit more use out of the gazebo. We just need a few more good sunny days for more barbecues!