Yep, really am using 1N4004's. When putting this together, I couldn't quite grasp the complexity of the diodes available. Trr is rarely listed on diode data sheets. So I used what it seems like other circuits posted on the Internet were using. From reading around, it looked like about 80% of the time, people were like "Anything is fine, 1N4004's are fine", and then the other 20% gave non-specific warnings that something better should be used. Never could I find a part# that should be used instead. So anyway, now I ordered some 1N5822's to try, but even that does not list trr on the data sheet! I am relying on the "Extremely fast switching" in the marketing section of the datasheet. Do you think 1N5822's will be sufficient??
Also buying an Aavid 566010B03400G heat sink. It seems that heat is normal and expected for the L298, but since I'm leaving this thing on all day now, and not real savvy about thermal engineering, I'm trying to play it safe by keeping the chip cool to the touch.
I am curious as to how you found the one you did? For a while I was looking for Multiwatt15 heatsinks, until I found some that would work at a local electronics junkyard (Apache Reclamation here in Phoenix, AZ) - I could find only certain things listed online for such heatsinks, but no pictures to see that they would actually work. Really, you could probably get away with a piece of bent and drilled aluminum stock. Remember to add heatsink grease, whatever your use!