Hi,
So a while ago I bought a TL866 and it came with a bunch of PCB adaptors to allow it to program non-DIP chips. I've used it a few times to backup EPROMs from old test gear (why I bought it in the first place) and I've had no problems, its been good.
However today I needed to use it to program some SOIC8 I2C EEPROMs mounted on a PCB - cool I'll just use the dedicated cable and clip that came with it.
Well.. so I thought. It always read zeros, and if I tried to program it, verification would fail on the first byte. bugger...
So after a lot of messing around, involving pulling a chip off the board in case it was something there, I hooked up the scope and what do you know.. yep SDA line is ground.. hum.. buzzed out the connections and there was a short on the board between Ground (IC pin 4) and SDA (IC pin 5).
So I fixed that and all was good!
This looks like it could be common as the ground track is very close to the pad.
So if you have one of these, do yourself a favour and just check for a short before you try to use it.
Ash.