Fixed short in Salora 22 inch TV
This TV was brought to me with the complaint that it no longer worked after the owner had used a too high voltage at the 12V input. Below photo shows the label on the back of this 22 inch TV.
Previous photos showed the matching Salora remote that also didn’t seem to work when tested with an IR diode as receiving signal sensing diode on the BNC input of my oscilloscope. And neither when tested on the IR detector of my LCR-T7 tester. Also shown were all signal inputs that are available on the leftside of this Salora. And this Salora TV also has a USB input port at the dvd insertion right side.
The Salora now indeed showed a completely shorted 12V input port when I used my 3A 12V Dreambox satellite receiver’s power supply to power the TV with a decent 12V voltage.
So it was time to open up the TV and inspect the boards. The short circuit was on the HV board.
Previous photo showed the dvd player board and the main board after the shorting HV module was removed for inspection. It was connected with a 6 wire white flatcable to the mainboard. And it had 4 HV output connectors for feeding the 4 backlight CFL tubes on the 22 inch LCD screen.
When measured on both e-caps next to both dual N-channel ME4946 mosfets they showed a very low ohmic short. Which most likely points to partly or completely defect now shorting mosfets. Assuming the shorting was not in the SAQ8818 pwm controller on this HV board but only in the mosfets it drives on its 4 pwm controlled outputs.
After both mosfets were removed with my Gordak hotair gun the short indeed was gone. So this must have been the only reason why the 12V input voltage short circuited. I did have many sop8 smd mosfets but not this one so it was time to order these. For about 11 euro I ordered 50 of them since they do not take up much space anyhow and are relatively cheaper when ordered as a set including the unavoidable relatively high shipping costs.
Previous photos showed the back of the HV board and of the mainboard with its 12V input port. Followed by a close-up photo of the dvd player board that also incorporates a USB input port.
When the mosfets arrived in just about 7 days the HV board was fixed and ready and the TV was working splendidly! But first I also had to fix the previously not working Salora remote before I was able to further test the TV. Which I did by re-soldering the resonator/quartz and its smd components before the remote finally controlled the Salora functions. Following last photos show the fixed and completely working 22 inch Salora TV.
Also the HDMi input port was tested and it showed an excellent picture of my connected quad-core computer. And last photo shows a final photo of the ready re-assembled and working Salora TV.
I also did measure on both removed mosfets and apparently only one mosfet was partly defect and completely shorting on its S1, G1 and both D1 connections. (which were pins 1,2 and pins 7 & 8).
So the second removed dual N-cannel ME4946 7Amp >60V mosfet was still fine and kept for future repairs.
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous article on 12V 3 Amp Power Adapter After About 5 Years Fixed Again
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Parasuraman S
June 29, 2024 at 5:05 pm
A good fix and a wise salvage too! Many thanks for a detailed article packed with useful info!
Waleed Rishmawi
June 29, 2024 at 6:31 pm
great work. thanks for sharing. 11 Euro for 50 parts? I think that not a bad price for these parts but how much was the shipping cost? any ways have a blessed day
Albert van Bemmelen
June 29, 2024 at 10:04 pm
The 50 small smd dual mosfets were 9.29 Euro alone. So the shipping cost was about 1.43 euro. Which often is the same shipping price when only a few of those parts are ordered. Why I bought 50 of them to make it relatively more interesting having to pay extra for shipping.
Yogesh Panchal
June 29, 2024 at 8:18 pm
Good job! Albert
Bill Shaw
June 30, 2024 at 6:45 am
Albert, always good to read your articles. In this case, I thought a couple of arrows showing where on the boards you were referencing would have been helpful.
Thank you.
Albert van Bemmelen
June 30, 2024 at 1:48 pm
I didn't want to elaborate on the obvious too much Bill, also leaving out the dual ME4946 N-channel mosfet datasheet and how the remote looked inside because it was all mentioned.
And the electric shock warning on the label here only warns for the HV power supply board, because there is no dangerous 230VAC power line input. Only 12V 4A DC.
Imoudu.O
July 1, 2024 at 4:33 am
I wonder why you refer that board as HV board when there is no 230vac input.Good that fet has making on it, in some cases they don't have.
Well thanks for sharing.