New 1260 Pump, higher ripple than expected

Just taken receipt of a new 1260 ISO pump, however the pressure ripple is much higher on this pump than 20 year old 1100 Quat and ISO pumps I have (0.5% @ 2.0 mL/min).

The new pump is producing a ripple of 0.5 to 0.6% at 2.0 mL/min compared to the older pumps of 0.0 to 0.1%.

Compressability settings are identical, similar back pressures, automatic stroke volume, same degasser channel. Purge valve frit and seal have been exchanged with no change.

Only difference between the pumps is no AIV on the new pump, but this should have no affect.

Any suggestions appreciated.

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