A while ago I reported problems in building Haillant’s VCA which features an LM13700. The IC got very hot and emitted a burnt smell, destroying a couple of capacitors in the process.
There was a discussion about whether there was something wrong with the build or whether the IC was the problem. As I could not find any shorts or possible mistakes (as the very helpful people in this forum suggested) and the build was done on a PCB by a reputable designer, I gravitated towards concluding that the IC was to blame.
Yesterday, I finally managed to put together an LM13700 tester circuit setup and tested the batch of ICs I got from ebay, against an IC that I bought from a reputable physical shop (many thanks to @SCGator for the pictures of his tester circuit and the resistor/capacitor values to build the blinker VCO).
The IC from the shop works as intended, while each of the ICs in the batch bought from ebay got hot, too hot to touch, within a few seconds (and did not produce the expected output). For what’s worth, here’s a picture with the working IC on the right, and one of the fake (?) ICs on the left.
To give a little more context, I looked up my files and found that I paid €3.57 for a single LM13700 in the shop, and $3.02 for 5 from ebay, so if the price looks a little too good to be true, then it probably is.