I finally fixed it. Here the summary: I bought a graphic tablet with a 21.3-inch Wacom Cintiq monitor broken down very cheap, although the previous owner did not know how to explain what symptoms I had. Besides, it didn't come with its external power source, so I couldn't study it to see what it had. So I followed these steps: 1. I jumped a 400w pc power source. and from there I took the 12 volts to power the tablet. I had to take it apart to see the polarity of the cables. I tried to turn it on and saw that the power indicator light turned blue and after a few seconds it turned orange, so I assumed that everything worked fine except the LCD lighting lamps. Even without that lighting I tried to see some image on the monitor but nothing was appreciated. 2. I measured the voltages that reached the inverter, and I saw that they were correct: 12 volts of power, GND and 3.3 volts of Enable when the tablet was turned on. This kept telling me that what was missing was the monitor lighting. 3. I inspected the inverter card and saw a capacitor that at first glance seemed in good condition, but I noticed under it a trace of ollin. I broke it up and it was effectively exploited. Also the only fuse on the card I could find was open. I thought about buying the parts, but the capacitor was 150 mF and apparently it is a non-commercial value, because I could not get it anywhere. I also couldn't get the fuse, but I was going to bridge it with an American 5 Amp. However, I measured the legs of other capacitors and saw that they were short. I removed all the capacitors and the short one persisted, so I was going to have to find out what the defective component was. I thought that the lamps were perhaps very old and that sooner or later I would have to change them, so I decided to definitely remove the entire card from the inverter and replace it with everything and lamps with an LED lighting kit, which I could get for 200 pesos . 4. Disassembled the entire monitor to access the lamps. That was the most difficult, because the LCD is very fragile. Fortunately I could do it. I removed the lamps and with instant glue I glued the LED strips (which I had previously trimmed to match their size). 5. The LED kit card came with 4 cables: the GND, the 12 V, one for ENABLE and one for DIMMER. The ENABLE I soldered it to the cable that was marked ON / OFF on the inverter; I DIMMER welded it to the ADJUST cable. And the GND and 12v I soldered them to their respective cables that were marked on the inverter. As all this I welded on the wires and not on the inverter card, I was able to discard the latter. 6. Before assembling the tablet, I tried it and I could see that it worked correctly. It may be strange, but I have become accustomed to buying devices whose price of new ones is too high, and that broken down I have found them extremely cheap and I have been able to repair them, such as laptops, cell phones and other monitors. This tablet originally costs 70,000 pesos and used around 30,000 pesos, but I could buy it for 900 pesos and repair it with 200. I use these elite devices not for vanity but for their characteristics that I require in my activities but whose price escapes my hands. I appreciate how little I know about electronics, because it has allowed me to access these devices.