One of my friend has the repair mobile phone shop in rural areas. He said he lived in a small village, the people has low income. But almost every house will be used cell phone because It is easy for us. However mostly used in older models Or the second hand, For economy.
And he was complaining the problems in repairing his mobile phone that not has the circuits, for comparison or as a way to repair that very old machine. Parts are hard to find, but he had solve the problem. By donating old machines. I carved into pieces and use them to try. Which is very time consuming. However, it is necessary when we has less resources. It must adapt to the situation. I just happened to save a link to download the Total Circuit. Although a long time ago. It is available I hope that it will be useful to you too.