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Tag: repair
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Another LCD TV repair
I repaired a Sodium LWD400-SI 40″ LCD TV, another case of defective capXcon capacitors that was sitting in a too hot power supply. http://kaizerpowerelectronics.dk/general-electronics/sodium-40-lcd-tv-repair/
Sodium 40″ LCD TV repair
Introduction
A friend of mine had this defective TV set and wanted me to take a look at it.
When plugged in the red led would light up and you could power it on to get a green led, but there would be no picture, just a black screen.
That it could actually turn on and go from red to green led could be a indicator on something wrong with the image / input boards, but as no back light turned on either I would start to take a look at the power supply.
The power supply is almost always the fault when flat screen TVs refuse to turn on.
Safety
WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.
Read this document about safety! http://www.pupman.com/safety.htm
What to look for
Taking the TV apart was no problem, just some few 30 screws around the frame and we are inside to view a main board and a power supply board.
The power supply was pretty compact and it was hard to see all the components for the heat sinks and plates covering them. I pulled out all the plugs and could measure +24VDC for the back light inverters, +12VDC for the image / input boards, but two of the four +5VDC only measured +0.3VDC.
There was one slightly popped 1000 uF / 16V CapXcon capacitor at top of the power supply. Hidden underneath the plate over the heat sinks was another four capacitors that looked to be in bad shape. No wonder when they are crammed in between two heat sinks with a roof, it would impossible to dissipate any heat from there.
I upgraded the all the capacitors to the same capacitance, but from 16V/25V to 35V/63V rated 105ºC capacitors. Capacitor life time depends highly on supplied voltage vs rating and temperature. By using capacitors with a higher voltage rating it should help them live considerable longer. I also moved that largest ones out from the heat sink trap. That two others was not as damaged and therefore I left them in their original place and now with a little better air flow with two capacitors moved away.
The popped CapXcon capacitors measured:
– 1000 uF / 16V: only 33 uF and 43 uF
– 470 uF / 25V: 215 uF, 300 uF and 453 uF.
I used capacitors that I de-soldered from other electronics to replace the popped CapXcon capacitors, turning the TV on revealed that it was fixed and now able to show a steady picture.
All I used was some common electronics knowledge, a soldering iron and 5 capacitors that I had from other old electronics.
Bottom line: I repaired a 40″ Sodium LWD400-SI LCD TV for free and spent about an hour on it.
TI-83 calculator repair
Published on: Jun 24, 2014. Updated on: Jan 05, 2018.
Introduction
I bought my Texas Instruments TI-83 calculator back in 1999 for when I took my HTX degree (Higher Technical Exam).
Since 2012 it began showing various symptoms of ageing that just got worse as time went on.
It could freeze during calculations and get stuck with dots moving in the upper right corner, as if it got stuck in a infinite loop, this could only be fixed by removing the backup battery.
It would not turn on at all, removing the batteries no longer helped and the calculator seemed dead, when I looked at prices for a new TI-89 I decided to repair my old one instead, despite it have some 20 dead pixels from a hard blow to display.
The freeze, unresponsive and suddenly dead calculator is caused by a flat ribbon cable connecting the two circuit boards in the calculator. There are some data lines with communication between them and when this link is disturbed it can freeze doing calculations or it just will not turn on at all.
Troubleshooting
If your calculator shows up with a black screen after a battery change, try to turn down the contrast setting by pushing the yellow 2nd button and arrow down button alternating.
The black screen appears because the calculator remembers your contrast setting that you gradually turn up as the batteries are drained, so when new batteries are in place they will light up the whole screen as they can supply full current.
Disassembling the TI-83 calculator
It is a relative simple repair that will require nothing more than a set of small screw drivers, flat and star will do even for the Torx5 screws used for the enclosure.
You will also need a knife, soldering iron, some thin wire and a steady hand.
The blue damaged pixels area is caused by leaking fluid from within the liquid crystal display, usually as a result of pressure or impact damage. Unfortunately this type of damage is irreversible and no amount of soldering or heating will fix it.
First remove the battery cover, batteries, backup battery cover and the backup battery.
Remove all six enclosure screws.
Remove the two screws holding the foil in place.
Locate the flat cable that connects the calculator unit to the display unit.
Remove the flat cable from the contact surfaces by peeling it off with your fingers, cut the black support ribbon with a knife and clean the contact surfaces for glue.
Solder a wire straight from each point on the calculator unit to the display unit. I used a single strand of copper wire from a multi core machine tool wire, nothing special, just a thin copper wire.
Almost as good as new!
Humax 40″ LCD TV repair
Introduction
I was taking a walk with my girlfriend when we came by a house with a 40″ LCD TV standing against the wall outside, on our way back to the apartment the TV was still standing there. I knocked on the door and asked if I could take it if it was just for the trash. I got it for free and they spared themselves a trip to the recycle station.
Dragging the 38 Kilogram heavy TV home was a less pleasant part of this great deal
Safety
WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.
Read this document about safety! http://www.pupman.com/safety.htm
What to look for
I turned the TV on and got a picture with no signal noise, but the back light was flickering at about 10 Hz making the picture absolutely useless to watch.
Taking the TV apart was no problem, just some few 30 screws around the frame and we are inside to view a main board and a power supply board.
Previous knowledge tells me that if there is a picture, noise or not, on the screen, the main board is okay. Looking at the power supply board it quickly became clear where the problem was to be found. 3 clearly popped CapXcon capacitors is likely to be the fault.
The red circles on the above picture shows where the three capacitors were located. The two large capacitors are the smoothing capacitors for the 24VDC supply to the back light inverter boards, these were measured to only 300uF capacity. The reduced capacity to around 1/5 of the original explains the ripple current in the 24VDC supply that makes the inverter boards emptying them before the power supply board can charge the capacitors. Thus making the back light flicker.
I found some 2200uF capacitors that I de-soldered from other electronics to replace the popped CapXcon capacitors, turning the TV on revealed that it was fixed and now able to show a steady picture.
All I used was some common electronics knowledge, a soldering iron and 3 capacitors that I had from other old electronics.
Bottom line: I got a free 40″ Humax LDE-40A LCD TV and spent about an hour repairing it.