lm7833 schematic
**broken link removed**
This is the board.Thanks for your replies.I'll post the picture soon. I forget to mention about the board, it's from Silabs and it's a mixed signal microcontroller 8051, but the board I had is the same, but it was manufactured in Shinghai,China. They manufacture Silabs MCU,development board and other things and supply them to Asia.The board was running fine, but when I tried to connect the development board with my custom made hardware, the development kit slowly deteoriate without me knowing, first case was seen, when I found 500mV AC ripple on the regulate output. I then look carefully at the regulator, I found out AMS1117 3.3V, where as in schematic manual Silabs had used LM2937 3.3V. I was stunned to see this, then I replace the regulator with a new one, it was LM7833 3.3V regulator. The board began to work perfectly, then within 2 days, I found out the MCU was getting Lava hot and the regulator too, then I realized MCU must have gone. Then I made a more shocking discovery, the PIN comming to header from MCU were routed differently from the one shown in the manual. I mean suppose if Vcc is coming on Pin3, then it was coming on Pin5. I followed the manual, but I didn't know the chinese board was different. Then I telephone the Silab Europe and I explain them my problem, then they said, email me, then I emailed them. I recieved answer 2 days later, then Silab Europe said, you are using Chinese verison of the board, I said I don't know if this board is Chineese or not.Then he showed me indication of it and it was then confirmed I had Chinese board, then I asked them for help, then they said, we have no consulation with Chineese Silab manufacturer. They might have made changes, but we are not known of any, they deal with it, so you better contact them, then I emailed to Chineese people ,waited around a week, got no response, then I telephoned them, those chineese guy were not even able to speak English. I tried to explain him in a very slow english, but his english was very poor. Most of the chineese I have seen are not good in English, even the team of Civil engineers Chineese I met a month ago, no body was good in English. So Chineese people were not giving me any response either on phone and neither on email, so then I place a phone call to Europe company again, then they said, I can't help you, if they are not helping, what I can offer is that, you buy our product, then we will assist you. As you see, we are not in co-ordination with Chineese company. My dad ordered that board from the internet. He didn't know all about these, if we would know, the board was about to come from China, we would never purchase from it and Chinese people had created problem. What they did, they used the European manual and changed the PCB accroding to their condition, if they had changed the PCB, then they must inform customer of their changes, but they didn't inform. Just because of them, I had accidentaly destroyed my MCU installed in the board, it wasn't my fault.My MCU got damaged, because of my custom made hardware connected on wrong PINS, it was correct if schematic was consult, but hell wrong in real, because PCB had different routed PINs. Then I made the new layout by checking the pins and output and made a new schematic, I then tried to replace the bad MCU with the new one I had, I then damaged the PCB while replacing the MCU, the face of the tracks are very badly damaged.Now I'm stuck, so that's why I'm making a new PCB.This was bad experience with Chinese company.
www.silabs.com European Silab
**broken link removed** Chineese Silab