Meopta meochrom head - what kind of bulb do I need?

Hello, I recently acquired a meochrom head for my Opemus 5, of the type described here: http://www.jollinger.com/photo/cam-coll/manuals/enlargers/misc/Opemus_5_manual.pdf

I do not have a transformator with it, but that seems to be easy enough to fix by dropping any transformator in front of it. However I don't know what kind of halogen bulb I need. This question is twofold: The manual does not describe the fitting of the lamp (which I suspect to be of the G6.35 or GY6.35 variety), and does not describe what color temperature the lamp should be. I am new to color printing and I remember reading that people use 4000K lamps, but I cannot find any of those in the Netherlands. The best I could find was 3400K; will this affect my ability to print in a meaningful way?

Could anyone, ahem, enlighten me on this matter? Maybe someone has experience with this type head, it seems to have been quite ubiquitous back in the day.

Thanks!

Hi, do you have a photo of the lamp house internals that might show the lamp fitting? My Meopta 'Magnifax 4' colour head takes the standard 12V 100W halogen lamp - https://www.amazon.co.uk/dp/B000N5MVAO?tag=duc08-21&linkCode=osi&th=1&psc=1 - although my example here is from the Philips 'Focusline' range.

I make colour prints and the standard 3400K lamps are fine.

Tom

Hi Tom, good to know that 3400K lamps are fine. My head takes lamps without reflector-though it is possible to take out the head's reflector and I suppose you can put lamps with reflector in it. Attached a photo of the lamp house.

Richard

aetios said:

Hi Tom, good to know that 3400K lamps are fine. My head takes lamps without reflector-though it is possible to take out the head's reflector and I suppose you can put lamps with reflector in it. Attached a photo of the lamp house.

Richard

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I see. I'd be tempted to keep the head as is, at least for the time being. RK Photographic in the UK might know as they distributed the Meopta products for a long time - www.thedarkroom.co.uk

I just took the plunge and ordered a 12v/105W transformator, and this lamp: https://www.osram.com/ecat/com/en/GPS01_1028526/PP_EUROPE_Europe_eCat/ZMP_56116/. I will report back whether it fits, for posterity. I won't be the last asking this question, I presume.

aetios said:

I just took the plunge and ordered a 12v/105W transformator, and this lamp: https://www.osram.com/ecat/com/en/GPS01_1028526/PP_EUROPE_Europe_eCat/ZMP_56116/. I will report back whether it fits, for posterity. I won't be the last asking this question, I presume.

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As you say, reporting back will add to the knowledge base here on Photrio.

aetios said:

I am new to color printing and I remember reading that people use 4000K lamps, but I cannot find any of those in the Netherlands. The best I could find was 3400K;

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There is no such thing as a 4000K halogen lamp. A 3400K model already is stretched to its limits so to say (overrated in other words).


(The melting point of Tungsten already is at 3695K.)

My spare Osram bulb for the Opemus 6 color is a Xenophot 64627 HCX EFP 12V 100W GZ635

AgX said:

There is no such thing as a 4000K halogen lamp. A 3400K model already is stretched to its limits so to say (overrated in other words).


(The melting point of Tungsten already is at 3695K.)

Click to expand...

I had honestly never given color temperature a second thought but put this way it makes sense. Guess we learned something fun today

Good news - the materials I bought seem to work, and the enlarger is now powering on and shining light!

I have two new problems arise now:
- The light takes quite a while to come on and power off. I think this is due to self induction in the transformer and I can probably work around it.
- The light that comes out of the enlarger is tinted distinctly yellow. This seems to be a repeat of [this] problem with exactly the same color head that came up a number of years ago. This mainly affects my ability to get blue light out of the enlarger; it stops at a rather weak and muddy blue light. I don't know how big this issue actually is all things considered but I have enough pointers to try and work it out myself should it cause problems.

For now I'm happy to know it actually powers on.
Summing up: A GY6.35 bulb fits, but felt a bit tight. Maybe G6.35 is better. For the transformer, I took a regular 105W 220v - 12v transformer and that seems to work but the light comes on and turns off slowly.

Thanks everyone who replied! See you around.

A 220V > 12V transfomer has too high voltage output with 230V mains of today,

The transformer says 220-240V; if anything the voltage is lower, I measured it and my (very cheap) multimeter told me it's about 8V under load.

It should be 12V under load.
There is no need for discussing colour-temperature of a certain type of lamp if the feed voltage is wrong.

I couldn't find the 220V 100 W transformer, so I connected two 220V 50 W in parallel and it seems to work.

What voltages are Photrio members seeing from the mains supply? I'm in the UK, close to a sub-station, and see around 245-250V.

I get typically 230V (today though 228V)


The 5% voltage rise I hinted at above in general is nothing to worry about, but with lamps that already are overated such can further strongly reduce longevity, thus rare lamps I only feed via a preceeding variac.