for those who use manual focus lens on eos camera will know "error 01" will happen when use it with a eos compatiable extension tube or tele-convertor.
i have attached here the modification for extension tube.
modification of tele-convertor is similar but more care have to be taken to prevent accidentally scratching the lens element.
pls note this modification is non-reversable.
1) tools needed
2) removing the coupling plate from the extension tube by unscrewing 4x screw
3) dis-assembled parts
4) *dont loose the spring loaded plunger pin*
5) modify the coupling flange, *note the orientation*