The analogue circuit board used in the ISA 428 MkII is exactly the same board used in the original.

Here is a summary of the changes made to the ISA 428 MkII:

• Analogue ‘moving coil’ peak meters have been removed.
• The Soft Limiter feature has been removed.
• The bit depth selection button has been removed from the front panel.
• The linear power supply has been replaced with a switched-mode power supply. 
  The new power supply automatically switches between input voltages. It can be plugged into most mains power supplies around the world without changing a voltage selector or a fuse.

The LED meters remain on the ISA 428 MkII and sit in the signal chain before the A-D converters.