1995 Stock Creepy Noise

[EJD799]

I know why the 1996 Stock makes the noise it does, but the 1995 Stock instead makes a really weird creepy noise when accelerating. Why is this?

 

[Edvid]

95 Stock trains are equipped with insulated-gate bipolar transistors, I believe because they were built after the 96 Stock trains (the switch from gate turn-off thyristors was made in-between the two builds).

 

[Sad Sprinter]

I know why the 1996 Stock makes the noise it does, but the 1995 Stock instead makes a really weird creepy noise when accelerating. Why is this?

This fantastic thread I started a few years ago might be if interest: https://www.railforums.co.uk/threads/alstom-onix-traction-system.177784/

 

[bramling]

95 Stock trains are equipped with insulated-gate bipolar transistors, I believe because they were built after the 96 Stock trains (the switch from gate turn-off thyristors was made in-between the two builds).

Exactly right. 95 was used simply because that was the original designation for the Northern Line replacement stock, but it was delayed by a few years due to budget issues. By all rights it should really be 98 stock.