Hi,

I have two Sound Blaster 16, a CT1750 with "good" DSP version 4.05 and a CT1770 with "bad" DSP version 4.12 (hanging notes in DOOM after 1-2 minutes).

As I need the SCSI interface (the box I've put the Sound Blaster in has only one expansion slot and no internal CD-ROM), I've decided to try swapping the DSPs between the two card.

I used a (cheap) hot-air rework station and desoldered both chips (at about 350C).

(The scratch marks are from my SMD tweezers which are too small for these chips and kept popping off)

I then soldered the chips swapped back in to the cards.

(I've now also cleaned the boards from flux after taking these pictures)

After plugging the CT1770 back in to the box, the SB16 was still detected by diagnose.exe and the DSP version shown is 4.05. A test with DOOM confirmed that there are no more hanging notes. 😀
And even the CT1750 still works, but now produces hanging notes, as expected.