[LargeFormat] Durst 138S focusing problem

[Don Wilkes]

At 10:16 AM 6/14/01 +0100, Clive Warren wrote:

>Good to hear from you - shame about the 138S.

Well, it's not fatal, just irritating :}


> From memory (the machines are not at this location) the focusing knob 
>moves small rollers against the centre column. Pulling the knob as a lever 
>allows gross movements up and down the column.

That sounds like the gross-adjustment lever, the ball-on-a-stick knob.
What's giving me grief is the round focusing knob, the one that has a
flip-out crank, for doing the final, critical focus.



>  Could it be the case that 
>the spring which holds the rollers against the column is misplaced or
weakened?

I'll check, but think it unlikely that they'd suddenly go 'soft' in the six
months I've had it.  It *was* working perfectly not that long ago!


>Lubrication is almost definitely not the solution - you may even have 
>lubricant on the centre column or rollers which could  well cause the 
>symptoms you describe.  Try cleaning the column and rollers.

Will do; thanks.



>Just to be technical for a moment - backlash means that the focusing knob 
>turns without any corresponding movement of the head up or down the column 
>- is this also happening?

It's actually the exact opposite of that.  After focusing 'up', and going
just a teensy bit too far, just breathing on the knob to focus 'down'
causes things to jump past the focus point.  Then I have to try to sneak up
on it again, and again, and again...

Cheers,
\dw