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  #21  
Old 21st November 2023, 01:34 PM
John King John King is offline
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Default Lpl7700mx

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Originally Posted by Dave Woodhead View Post
Hello from Nottingham. Brief intro, I've been learning and practicing for the last 12 months printing b+w on a DeVere 504 at a community darkroom (Make It Easy Lab). Just light proofed my spare bedroom and bought an LPL C7700MX. Seems I've fallen down the rabbit hole...
The hole may be deep but there is light down there. The LPL7700MX is my enlarger too and have had it since 2000 when I changed it from a Leica 35mm only enlarger.

So far I have only encountered one problem and that is with the ceramic bulb holder and they can corrode inside where the pins of the bulb are inserted. New LPL ceramic holders as far as have found are non obtainable although ones used for Kaiser and possibly Durst colour enlargers are the same design and can be spliced into the present wiring although getting to where the ends are inside the enlarger head is a complicated task to strip down and rebuild. (I have a spare head and one day when I become exceedingly bored I will try to take it to pieces to see where the wires are attached to.)

The symptoms of corrosion are flickering of the bulb when it is switched on. I got around this by ensuring the pins on the bulb are completely clean then applying a very small coating of solder to each pin which ensured a good contact and circuit.

Also check that the head is completely perpendicular to the baseboard using the screw adjuster under the head which allows the head to turn for horizontal projection and the column if it is found out to be out of kilter this can be adjusted by loosening the securing bolts and using pieces of card to shim the column to get it vertical.
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  #22  
Old 22nd November 2023, 09:02 AM
Dave Woodhead Dave Woodhead is offline
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Thanks John, my bulbís not flickering (yet), good to have a known solution to the potential issue. I was thinking about alignment and how one goes about squaring everything, as thereís no obvious adjustment knobs. Do you use a particular method or device for calibration? Iíve read about two mirrors, or a laser, but Iíve never got involved before as Iíve only ever used other peopleís enlargers.
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  #23  
Old 22nd November 2023, 10:12 AM
John King John King is offline
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Quote:
Originally Posted by Dave Woodhead View Post
Thanks John, my bulb’s not flickering (yet), good to have a known solution to the potential issue. I was thinking about alignment and how one goes about squaring everything, as there’s no obvious adjustment knobs. Do you use a particular method or device for calibration? I’ve read about two mirrors, or a laser, but I’ve never got involved before as I’ve only ever used other people’s enlargers.
Firstly make sure that the baseboard is level which is easy using a spirit level. You don't need anything special, but one made from metal is probably better. It doesn't have to be a laser type and in any case they can cost a lot more so a basic one will do just as well, but make sure you can check horizontal surfaces AND vertical ones. Check the level across the board and fore and aft. If you are really fussy you can check on an alignment from corner to corner If there is a discrepancy you can level it up by shimming the board with pieces of thin card under the small feet on the underside of the baseboard.

Now check the main column using the vertical position on the spirit level. Check from the top and centre positions on the column, on side and from the front. The little bubble should be as near as dammit in the centre of the glass tube. As I said in my previous post if the column is out of true, loosen the screws that secure the column the adjustment can be made using thin cardboard shims. They should be slightly thicker than what is actually needed because when you retighten the screws it will compress the card.

Now check the accuracy of the enlarger head by removing the lens (if one is fitted) and placing the level under the casting immediately below
the centre where the lens would be. If you have the column and baseboard aligned, the for and aft check should be completely neutral, in other words spot on.

Under the lamp-house at the back, but in front of the column there is a large gnurled knob which is there to loosen the head if it needs to be removed. There is also a casting on the head with adjustment indicators and a pointer which can be a guide to getting the head level in the sideways aspect.

To be blunt this is actually quite crude and the only way I have found to get real accuracy is to centre the pointer with the central cast marking and check. If it is out of adjustment, just slightly loosen the gnurled knob and manually move the head just a touch and then check with the spirit level. The one on mine was actually quite a way off. You will only need a minute movement and after each movement check again. Once you have the bubble central, just tighten the knob securely and the jobs a good'un.

Now make a large print from each of the of the corners of the negative with the lens stopped down to F8 (for 35mm or F11 for 120 ) If the appearance of the grain is even with all 4 small prints, the enlarger is aligned accurately. If there is a discrepancy it may be because you are using a glassless negative holder so this may be corrected by using a carrier with glass inserts.

Last edited by John King; 22nd November 2023 at 10:27 AM.
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  #24  
Old 22nd November 2023, 02:30 PM
Dave Woodhead Dave Woodhead is offline
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Amazing, thanks John, will follow along. I'm using the universal carrier with glass inserts so that's one variable omitted. Nice one.
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