Quoted from barakandl:
Maybe the leg rot that happens on these chips gets up inside of the chip package and effects something or just they just always sounded different from day of production... not sure
That's an interesting point, I wonder if they degrade/change over time.
I bought 7 NOS TMS5200NL chips nearly 20 years ago & I tested them when I got them, all the same date codes, I think 3 or 4 out of the 7 appeared to be faulty with garbled speech, the rest were ok, I sent them back & they sent me replacements - I remember when I had 7 working chips they did all had the same pitch when tested in the same board.
None had any leg oxidization when I got them, but I noticed recently that most now have a bit. I decided to vac seal the 6 of these I still have in a tube to halt this - this may be a first!
Also, going back earlier to around 1997, before their were any sellers on the net for chips like this, I needed a TMS5200 & could not find one anywhere or even a used S&T board at that time, so I bought a TI99 speech synthesizer which are cheapish & utilize a TMS5200.
Interestingly when I pulled the unit apart it had a different part number for the chip - CD2501E. It is funtionally identical to the TMS5200, just a different number. Works perfectly. That chip has also oxidised. No NOS CD2501E chips can be found anywhere.IMG_0771 (resized).JPGIMG_0773 (resized).JPG