Durst M-805 loses the focus.

[Henry Alive]

I have a Durst M-805, condenser type for Black and White Photography.
I have noticed that my enlarger is not able to keep the focus for a long time. Let me explain a little bit. I put the negative in its place and then I focus easily the image on the paper surface located on the easel. However, after some minutes, the negative is out of focus.
I have investigated what is going on, and I have noticed that the enlargers head goes down a little bit, even though I lock any nut or similar thing that should be locked. It seems to be a problem with the counterweight of the enlarger. Can you tell me what I can do?
Thank you for your comments,
Henry.

 

[Ian Grant]

There's some friction pads that need tightening on the stage that carries nthe head, these wear and the head creeps up the column usually, if the counter balance springs weak I gues it would drop These are on the back of the enlarger.

Then there's a cruder adjustment on the focus mechanism, should be a simple screw/felt pad.

Ian

 

[ic-racer]

If the head moved down a little at at time by the next morning it will be all the way down. Is that the case?
Otherwise try to warm up the negative with the lamp on. Once the focus has stabilized put the lenscap on. Then put the paper down and quickly turn off the lamp, take off the cap and start the timer.
Otherwise, look for a glass carrier.

 

[Henry Alive]

I want to thank both of you for your answers. I have to say that the head does not move as much as to be all the way down. In fact, I have just observed a very small movement of the complete head assembly toward the easel, as I recover the focus rolling very little the fine adjusting wheel to make the lens go up. I have also checked that the lens does not move in relation to the rest of the head (or negative).
I am going to check the state of the friction pads, nuts, springs and any other thing located on the bag of the enlarger. Otherwise, I will try with a glass carrier, even though I prefer to work without glasses.
Thanks again,
Henry.

 

[Ian Grant]

Henry, from memory on the enlarger I had issues with the friction pads are beneath the cover on the back where the hadle for raising & lowering the head is located. There's nothing fancy just a simple tightening up takes a minute or two thats all.

Ian

 

[ic-racer]

I'm not sure how big you are printing, but to go out of focus enlarging a 35mm negative to 16x20 at f8 the head will have to fall about six centimeters to see any effect with a grain focuser. I'd search on 'negative pop.'

 

[Ian Grant]

I'm not sure how big you are printing, but to go out of focus enlarging a 35mm negative to 16x20 at f8 the head will have to fall about six centimeters to see any effect with a grain focuser. I'd search on 'negative pop.'

It only takes a very small amount of creep and the print lose sharpness, I had this happen with a Durst M601 quite a few years ago. Your forgetting that any shift during exposure will change the amount of enlargement of the image no amount of DOF in the enlarger lens can correct that.

Ian