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

[aetios]

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!

 

[Tom Kershaw]

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

 

[aetios]

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

 

[Tom Kershaw]

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

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

 

[aetios]

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.

 

[Tom Kershaw]

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.

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

 

[AgX]

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;

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.)

 

[Martin Rickards]

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

 

[aetios]

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.)

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

 

[aetios]

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.

 

[AgX]

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

 

[aetios]

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.

 

[AgX]

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.

 

[Martin Rickards]

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

 

[Tom Kershaw]

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.

 

[AgX]

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.