I'll toot my own horn on this one - The repro boards are right here on pinside
https://pinside.com/pinball/market/shops/1297-glodstone/04572-vsu-2-speech-board-replacement-for-vsu-100
However with no speech at all, you may want to check dip switch #17 on the mpu and make sure it is on!
Also:
Quoted from Xtraball:I can get that same loud screech if I turn off my Flight 2000 and then turn it on again right away.
TheLaw is right, that its unfortunately normal. That loud sound is greatly reduced on the repro board. Others have reported reduced background hum too