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I just made my first tentative foray into the murky world off SSTCs,
with the not unexpected release of the "magic smoke" when a MIDI
controller got stuck on a high pulse rate, before I could turn it off.
The coil is a "Screamer" built by Tom Blitch in 2011. Tom's web site
has disappeared, but I do have schematics.
The schematic calls for HGTG20N60A4 IGBTs. However, the schematic image
shows them as having the built-in reverse protection diode, which I
think would make the actually HGTG20N60A4D units.
I'm pretty sure I can substitute the -D units for those installed, but I
noted that the manufacturer recommends substituting HGTG30N60A4D units
for the original IGBTs.
The newer 30N60A4D units have twice the current capability, which might
let them live a bit longer. The only unfavorable difference I can find
on the spec sheets is that the turn off time is 38 ns for the 30N60A4D,
compared with 32 ns for the 20N60A4D chips.
Would the extra 6 ns of turn-off time be expected to make a significant
difference in operation?