Having problems with your Computer Monitors ?

Yuraku LCD TFT Monitor MA7BBA Wont power up

\015 Hi brought 36 of the above monitors we now have 11 dead ones so they all seem to go pop, Yuraku will no longer fix them they will not collect them even thou RMA is faxed etc! fault must be a common diode but no one says which one? Im happy to go to Maplins and solder etc, but no idea which diode/component is faulty!\015\012Other monitors like MA9BBG has same fault so it must be easy to find and replace, If it was one I would not bother but so many with same fault!!\015\012\015\012Cheers and good luck!\015

Answers :


I've had the diods problem on such a monitor recently. To fix it I had to change the fuse and two 1N4007 diods as you can see on the following page:

You will notice I mounted the replacement diods on the solder side ( second hand components with too short leads) and that only 3 diod locations are seen on the component side; the fourth is hidden under the transformer on the top side.

Hope this can still be of any help.
I first tested the 1N4007 diodes as per tux12's solution. In my case, these were not the faulty diodes.

Next I turned my attention to the large Schottky diodes toward the top end of the power supply. There are two SR560 diodes in parallel on the left, in parallel. (The SR560 is rated for 5 amps, and can handle a peak reverse voltage of 60 volts, RMS 42 volts) Above them is a small capacitor. On the right are two SR5100 diodes in parallel (similar to the above, but rated for a peak reverse voltage of 100 volts, with a large capacitor above them.

I removed the Schottky diodes from the circuit and tested them with a multimeter on the diode setting. On the good diodes, I had a reading in one direction and no reading in the other direction. On the bad diode I had a very low reading in both directions. This was obviously the faulty diode.

I swapped in a fast-switching BY500-800 (rated for 5 amps, max peak reverse voltage 800v, rms reverse voltage 560v - possibly overkill, but I thought I'd try it and see what happened) and that replacement seems to have done the job fine :)
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