[DTech]

I prefer to have it there, since ori one had it even if the chinese invention works also.
@sixcode if that picture is from your real vas, you might want to look at 1977EFE that needs to be replaced with 1976 model and also around it you have one extra capacitor, i think is china bonus.
LT1976 - High Voltage 1.5A, 200kHz
http://cds.linear.com/docs/en/datasheet/1976bfg.pdf

LT1977 - High Voltage 1.5A, 500kHz
http://cds.linear.com/docs/en/datasheet/1977fa.pdf

The difference between the LT1976 and LT1977 is that the fixed switching frequency of the LT1976 is 200kHz vs 500kHz for the LT1977.

The switching frequency affects: inductor size,input voltage range in continuous mode operation, efficiency,thermal loss and EMI.