# Optical Forums > Optical and Ophthalmic Equipment >  power drum sliding on B&L 70 lensometer

## morinput

I recently acquired one of these in terrific condition with one exception, the power drum slide tension is too loose.

I seem to remember having a similar problem with one years ago and it being a pretty easy fix, but I have the cover off and I'm not seeing it. Can anyone assist? Bonus points for pictures :)

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## Howard Gorin

There is a friction adjustment under the instrument.  Unplug the Vertometer.  There are two small screws that hold a cover on the bottom of the instrument.  Try not to loose the little screws, they are a sort of uncommon thread size like most of the screws used on the instrument.  You will see some setscrews that press on a flat spring that presses against the power shaft, tighten the screws slightly to put more pressure on the spring

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