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  #1  
Old 29th October 2016, 09:43 AM
John King John King is online now
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Default Massive filtration change

I thought I had seen everything with colour printing but what happened this morning is a new one on me and I cannot see any logical explanation.

With my current mix of RA4 developer (Kodak Ektacolour) which has had very little through-put, say about 10 sheets of 10x16 and adequately replenished after each session (10cc per every 80sq ins as recommended)

I made a print yesterday which I thought was OK but after examination in daylight today, I could see it still had a slight cyan colour cast. I started printing and made another test strip using 65m and 50Y which was the filtration I used last time. The result was the same. I then altered the filtration to add more red = take away 5M and 5Y. The next print was spot on.

I went to check the focus before I made a full print but the enlarger would not light up although the lighting for the filtration windows did. I assumed it was the bulb had blown, so stripped the housing down to replace it but to me it looked fine. The bulb itself is also relatively new - less than 3 months old and not used a great deal.
When I switched it on again it worked for a second or two then stopped.

To cut a long story short I turned the bulb around so that the two base pins fitted back into the base, but in opposite holes. I switched it on and it was now working again so re-assembled the housing and set about to make a confirmation test print -'just in case'!

The resulting print now had very a very heavy red cast. just as if the filtration had been completely removed. But nothing had been changed, filtration was the same as before, it was just that the print was a different colour! It was however over exposed!

The lever to remove the filters out of the light path was working correctly and in place. I have eventually managed to get the filtration back on track, but it now requires 125M 130Y, about double that I was using before. The exposure I was using previously was also back to what I was using before the hiccup (16 seconds) despite the increase in filtration values.

Basically I am stumped to what the problem was, it was sudden, not gradual and appears to be due to the bulb. Unfortunately I don't have a spare to test.

Any ideas?
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Old 29th October 2016, 10:23 AM
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Jon Butler Jon Butler is offline
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John,
It's the bulb.
Jon
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http://real-silver-prints.com/

"I Prefer it in the Dark"
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Old 29th October 2016, 11:02 AM
John King John King is online now
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But the sudden and very dramatic change? I have never come across this before. A gentle change over the life span of the bulb as per my previous ones, but a step change in one fell swoop?

I don't know. I have ordered 2 on line so I should be able to tell next week.
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Old 29th October 2016, 03:32 PM
John King John King is online now
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Default Non the wiser.

I have stripped down the enlarger colour head and found nothing wrong. The dichroic filters are all moving up or down as they should and go to the ends of the scale. They are clean as is the light diffusing box. The only little problem I found was the illuminating bulbs for the filtration scales were a little loose.

The main bulb ws removed then placed it back in the original position it was in before the problem and now it works normally, but why moving the bulb and turning it 180 degrees should have such a dramatic effect... I simply don't know. The filtration is back to normal with no colour shifts over a 12x16 print.

I'm still baffled! (I do know a bit more about the interior of the enlarger though!)
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Old 29th October 2016, 03:49 PM
alexmuir alexmuir is offline
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Might it have been an issue with the power supply/transformer? Perhaps the voltage to the lamp was reduced?
Alex


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Old 29th October 2016, 07:10 PM
JohnX JohnX is offline
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I had a lamp once that had a broken element, sometimes it lit and sometimes it didn't, with varying amounts of light output.
The element was broken, it was resting on its supports and/or resting on another portion of the element, either way, the connection was good sometimes and sometimes it wasn't, which provided a few hours of heads scratch entertainment till I figured it out..
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Old 29th October 2016, 08:20 PM
Mike O'Pray Mike O'Pray is offline
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John, we and you combined may never get to the bottom of what was the cause but like the others I suspect the bulb or but less likely the transformer.

I have a Durst 605M and my bulb's prongs fit into a ceramic holder(female). Over time it seems there is arcing inside the female part and this affects the bulb's output until eventually the bulb's output can fluctuate during the exposure.

It may be that simply putting the prongs in the other way round has "cleaned" the female part and enabled it to give stable full power.

This is all really speculation on my part based on my Durst and I have no electrical knowledge to back it up but if your prongs fit into a ceramic holder it might be worth giving the prongs a rub with emery paper or small round file and the inside holes a scrap with the largest sewing needle that will fit

Best tool would be a very thin round file that fits inside the holes if you have one but a sewing needle did work in my case

Eventually the ceramic part may need changing. There was a seller on e-bay for the ceramic part for the Durst. It may be that this ceramic part is the same for all or most enlargers and might be obtainable

I am not sure that the "gunge" caused by arcing inside the ceramic holder's holes and now "cleaned" would be enough to double your filtration. That's a lot of "subtracted"red in your new filtration.

Do all the negs on that film, if shot in similar light and having a good range of colours need the same extra Y and M now the bulb is working?

Mike
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Old 29th October 2016, 09:09 PM
alexmuir alexmuir is offline
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This is a good point Mike makes about the bulb holder. I've had trouble with this type of holder in other applications. You have to be careful cleaning them though, as the ceramic part is easily damaged. Electrical contact cleaner may help.
Alex.
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Old 29th October 2016, 09:16 PM
John King John King is online now
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Default Normal filtration

I am using Kodak Endura paper cut from a roll and not Fuji pre-cut and the filtration is significantly different. As I said, after putting it all back together I did a test strip using the heavy filtration that I had been required after the 'problem'. It was heavily under exposed even though I used roughly the same times as before. Not only was it under exposed but was strongly cyan.

I reverted to the original filtration I had been using before it went belly up and the results were just about spot on, only needing a bit of cyan removing. I was back to the same exposure range also. (22 seconds at F8 for a 12x16 print from a 6x4.5 neg) Final filtration 55M 45Y. pretty well as I would expect it to be.

As for the bulb and base unit, the base is just like a new item. On my previous enlarger (LPL6700) the base was quite discoloured and rough compared to the present one. Infact the interior of the enlarger is prestine! The pins on the bulb are uncorroded and slide into the base easily, there is no roughness at all.

What I have done is push them in and out of the holder a few times after wetting the pins with WD40 and finally rinsing them off with quick drying automotive electrical cleaner. There was very little deposit.

It's all back together now but I will swap the bulb over when the new ones arrive.

P.S. For those who still do RA4 printing. Make yourself a dispenser for a paper roll. I am using a 12" x 88M roll from AG Photographic (about £89 and disregarding wastage I can cut around 200 sheets of 12x16. That's about 1/2 to 1/3 the cost of buying ready cut Fuji, which I don't like anyway. Once you have got the knack of cutting it, it is easy.

Last edited by John King; 29th October 2016 at 09:27 PM.
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Old 30th October 2016, 08:29 AM
John King John King is online now
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Default Transformer

I forgot to add I checked the output from the transformer with a digital test meter and there was a steady output to the enlarger of 12.21V
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