Why does my ps3 get ylod?

So I want to tell some weird things that happend. I bought a PS3 with a first red blinking light. I tried to start it and it gave the l red blinking light which meant I had to clean the inside. I did that, put everything back together. After that I started it again and guess what? It started and kept staying green. Only thing was, it didn't give any output at hdmi at that moment. I didn't have another old cable to test it if that would work. I thought lets replace the thermal paste as well cause it was already an old ps3. So I put new thermal paste and ever since it doesn't run and keeps giving ylod. Can anybody maybe help me or give some advice?