Quote Originally Posted by HenrikOlsson View Post

Another possibility is bad chips, where did you get them? EBAY?
chips came from three separate supliers (farnell aka element14 ,rs components and a local supplier) they all look identical so I can't tell which is which any longer ,
the rs232c inputs are floating and the rs232 outputs are not connected to anything for the test process .according to the data sheet the cmos/ttl level inputs have no internal pullup and need to be not left floating , the rs232 inputs have internal pull down resistors so I'm assuming these can be left o/c (surely). I got a bunch of soic (smd) pack ones on ebay too but these have not been tested yet.
I have only tried 1uF caps but three different types. I'm at a loss to understand why they sometimes fail to work but after a few power on/off attempts they work (for days ) until the next power up