This is a post about a simple fault that has been puzzling me for the last few weeks. Perhaps it might save someone else a lot of wasted paper.
I have been finding my prints inconsistent; wildly so in fact. Prints have not been responding as predicted to changes in exposure or contrast. This became so extreme (and so obvious) that when I put 2 prints next to each other, one exposed for 1/2 a stop more than the other (both the same grade) they appeared identical. I changed all of the chemicals in my Nova slot processor as I thought the developer might be exhausted but that did not remedy the problem. After this went on for about a week the bulb blew. I changed the bulb and thought the failing bulb must be the explanation for the odd prints. It was not the explanation and the problem continued.
Then I noticed that during an exposure the light was varying in intensity. It was actually difficult to see this. I thought it might be the transformer so I swapped it for a spare I have. That didn't help. Then I thought I would check the bulb again and discovered that one of the wires to the ceramic lamp holder was loose (this enlarger uses a GZ6.35 12v 100w Xenon bulb). The wire was so loose that it came straight out of the lamp holder with the lightest pull. Unfortunately, the lamp holder had no clamping screws to hold the fly leads in place. It must have been fitted at the factory with some method I cannot replicate so I had to order a new lamp holder and new high temperature (200 degrees C) double insulated fly leads (the end of the loose fly lead was burnt and corroded, stripping it back further did not reveal good copper). I installed the new lamp holder (which has clamping screws for both the fly leads and the pins of the bulb) and suddenly everything is back to normal. Hurray! I was beginning to think that I had completely lost the ability to make a print! The fix cost £8 for the new parts.
PS If anyone wants to replace the bulb holder and leads in this type of enlarger there is an easy way to to do it. When you take off the access panel (black metal finned heat sink) to get to the bulb you can see that the enlarger is constructed with a plastic outer case screwed to a metal inner chassis. There is a hole in the right hand side (looking from the front) of the inner chassis designed to allow a long screwdriver through to undo the screws of the ceramic terminal block. To use this access for a screwdriver you need to remove the right hand half of the plastic outer shell. 3 screws secure the right hand plastic case along with the handle for the filter "in/out" (there is a spring washer under the handle). Obviously turn off the power and unplug the enlarger from the transformer before opening anything up. You need to take the head off the enlarger to take the outer plastic case off. The factory fitted leads to the bulb are high temperature (200 C) double insulated and so if replacing they should be the same (or better) specification. Ordinary leads will melt (or at least the insulation will melt).
I have been finding my prints inconsistent; wildly so in fact. Prints have not been responding as predicted to changes in exposure or contrast. This became so extreme (and so obvious) that when I put 2 prints next to each other, one exposed for 1/2 a stop more than the other (both the same grade) they appeared identical. I changed all of the chemicals in my Nova slot processor as I thought the developer might be exhausted but that did not remedy the problem. After this went on for about a week the bulb blew. I changed the bulb and thought the failing bulb must be the explanation for the odd prints. It was not the explanation and the problem continued.
Then I noticed that during an exposure the light was varying in intensity. It was actually difficult to see this. I thought it might be the transformer so I swapped it for a spare I have. That didn't help. Then I thought I would check the bulb again and discovered that one of the wires to the ceramic lamp holder was loose (this enlarger uses a GZ6.35 12v 100w Xenon bulb). The wire was so loose that it came straight out of the lamp holder with the lightest pull. Unfortunately, the lamp holder had no clamping screws to hold the fly leads in place. It must have been fitted at the factory with some method I cannot replicate so I had to order a new lamp holder and new high temperature (200 degrees C) double insulated fly leads (the end of the loose fly lead was burnt and corroded, stripping it back further did not reveal good copper). I installed the new lamp holder (which has clamping screws for both the fly leads and the pins of the bulb) and suddenly everything is back to normal. Hurray! I was beginning to think that I had completely lost the ability to make a print! The fix cost £8 for the new parts.
PS If anyone wants to replace the bulb holder and leads in this type of enlarger there is an easy way to to do it. When you take off the access panel (black metal finned heat sink) to get to the bulb you can see that the enlarger is constructed with a plastic outer case screwed to a metal inner chassis. There is a hole in the right hand side (looking from the front) of the inner chassis designed to allow a long screwdriver through to undo the screws of the ceramic terminal block. To use this access for a screwdriver you need to remove the right hand half of the plastic outer shell. 3 screws secure the right hand plastic case along with the handle for the filter "in/out" (there is a spring washer under the handle). Obviously turn off the power and unplug the enlarger from the transformer before opening anything up. You need to take the head off the enlarger to take the outer plastic case off. The factory fitted leads to the bulb are high temperature (200 C) double insulated and so if replacing they should be the same (or better) specification. Ordinary leads will melt (or at least the insulation will melt).
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