Replacing 12V 75W Enlarger bulb with LED upgrade...??

I'm currently trying to fix a Leica V35 Focomat enlarger which has a bad transformer. The info
on the particulars of the old transformer are not readily available, and here in the U.S, it's becoming
quite frustrating trying to get the parts to do a work-around...Leica changed bulbs later in the
production due to the original buld no longer being available...a kit was required, but basically an easy fix.

These bulbs are about $30 each, not a biggie...if your system works. Leica no longer have the transformer.
So I got to thinking...with the new LED technology, why couldn't I just bypass the 12V step down and
simply go with a 120V LED replacement, upgrading the socket system etc.

Does anyone know what differences in light quality, if any, that there would be with LED vs the original Halogen?
If I can duplicate the 3400K of the Philips 13139 bulb, it should be the same right?

Jason

You may need to upgrade the wiring too. 12V wiring likely has a lower insulation rating. Using 120V with 12V wiring may present a shock hazard. 18ga wiring with 300V rating is inexpensive and easy to work with.

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I checked bulb size and the newer style bulbs should fit into the Leica upgraded bulb fixture. Good point on the wiring...I had planned on replacing the wiring anyways...thanks Mate. I think an LED of about 1100 Lumens should be equal to the original 75W bulb...it will be a slightly different color temp, but with B&W, that won't be an issue as far as I can determine. I'm sure the old bulb is in the 3400K range...so if I can get close, shouldn't affect filtration.

You will still need a power supply for the LED lamp. I'd think that LED would be the expensive way to go. If you are on a budget, you could use these 76 cent 75watt halogen lamps. https://www.1000bulbs.com/product/5...77UsrOZ8V8dURCGYZmb86unXod28EErOL3hoCK2zw_wcB
In terms of power supply, if you are having trouble locating a 75VA transformer that fits in the v35 base, you could also look at a switching power supply. Those are much more common and could be small enough to fit inside. It could be placed outside the base also.
http://www.halogentransformer.com/r...tYnaPp9DuDwNTz4JNWmeivEWjMficNQIqGxoChnjw_wcB

Voltage is not the issue, its the current rating, how many amps.

Finding an LED bulb that fits the Focomat without modifications will be a problem. LEDs can't get too hot and therefore the LED bulbs always have a heatsink built in. The more power, the bigger the heatsink. A 75 W halogen bulb would be approx 1500 lumen (20 lm/W). An modern LED can do about 100 lm/W so you'll be looking at a 15-20 W LED bulb but in a small MR16 (12V) or GU10 (120V) form. I don't think that these exist (yet?). There simply is not enough space for a sufficient heatsink. So LED bulbs that do 1500 lm are too big. Some of the Philips MR16 bulbs even have a tiny fan built in but only go up to 300 -400 lm. You can built something yourself with a COB LEB, a lens/reflector, a LED driver module and a heatsink but it won't be plug & play into the existing socket of the Focomat.

If the transformer is the main problem, just get a non-Leitz transformer and keep it external to the Focomat. As IC-racer suggested, a switching power supply can also be an option but beware that these things usually don't switch on immediately. There's often a delay of up to 0.5 s. Not a big deal if your exposure times are well over 10 s or simply always add a 0.5 s extra time on your timer.

The enlarger contains "no user serviceable parts" in the base, so if you don't have experience repairing this stuff, it will be tough going. Transformers only transform AC, that is basic physics; like gravity. Watts is Amps x Volts; also pretty basic stuff. Incandescent lamps light when connected to both AC and DC, this information predates the introduction of sheetfilm. ( http://www.pbs.org/wgbh/americanexperience/features/general-article/light-acdc/ )

The fuse is on the primary, so 240v and 0.6A fuse for them and 120v and 1.0A fuse for us. Conservation of matter and energy is pretty basic stuff (I did not add the crayons to the below illustration) dictates the fuse only needs to be 1 amp if it is on the primary (that allows up to a 120W load, so it won't blow with the 75W lamp). Aren't transformers cool?

http://image.slidesharecdn.com/9-3t...2/95/93-transformers-13-728.jpg?cb=1272285896

In some non-photographic fixtures, I've replaced large, hard to find, toroidal transformers with much smaller electronic ones like this. Not sure if it would work for you or if these electronic transformers have stable enough output.

Then there's this: (there was a url link here which no longer exists)

Swapping the wiring no problem. Why though if it's not deteriorated? The original lamp was 75W/12V as is the replacement.

Wouldn't it be possible to use LED's mounted above the lamp housing with a 45 degree mirror redirecting the light. Plenty of room
for The LEDs and any V converters needed.
Wouldn't have to be LEDs, it could just as easily be tungsten or halogen.

RE: 45 degree thing. Durst used it in many of their enlargers but with the lamp horizontal and the light directed downward.

The transformers in classified are in the UK. Would shipping be $$$? Easier to change to an external xformer.

It would be difficult to hack the Focomat lighting system without affecting the even distribution of the light and it's usability with any of the filtration heads (either VC or CMY). The filters, diffuser and the condenser are all part of that system and the whole thing is tiny and heavily made.

As 12v halogen lamps are widely used, and the power supplies are widely available, can't you get one from a shop outfitting electrician for example? The bulb availability problem can also be helped by replacing only the bulb envelope instead of the entire reflector, as HERE. Remember that the reflector is not the same as a normal household device - it has a non-standard focus point (there's a tiny hole in the diffuser box which the light must go through) and a silvering which allows IR radiation to go right through it, hence reducing heat build-up in the lighting system.

A while back I tested a number of MR16 lamps with different reflector configuration in a diffusion enlarger. The efficiency of the lamps varied by the evenness of illumination was not affected. Can you share the results of your tests showed reflector configuration affected the evenness of the light output?

You need to do some research on the spectral output of any LED substitute. While the output of incandescent bulbs is continuous the output of an LED may not be. Any discontinuity could cause problems with color or VC printing. What the human eye perceives as white light may not be what photo materials see.

http://www.lighting.philips.com/pwc...versity/internet-courses/LEDs/led-lamps5.html

ic-racer said:

A while back I tested a number of MR16 lamps with different reflector configuration in a diffusion enlarger. The efficiency of the lamps varied by the evenness of illumination was not affected. Can you share the results of your tests showed reflector configuration affected the evenness of the light output?

Click to expand...

Presumably that was for me?

The main difficulty with adapting the V35 head for anything different is the compact size, it is designed down in size to a really great extent. The use of the wrong bulb (hence wrong beam) causes a lot of light to miss the hole in the colour-filter section and not get as far as the mixing box and the excessive radiant heat reportedly overheats the whole head. If you try to replace the whole of the back of the enlarger head, behind the filter system, in order to fit a completely different lamp system then you will need to be very careful indeed with alignment, as the mask behind the filters is the same size as the hole in the mixing box but also quite far away - it would be easy to cast a shadow from the filter system in to the mixing box.

I have not had to do any odd tests with incorrect bulbs as, happily, I have the adapter kit to take the current bulb, instead of the discontinued 6604. I only bought the (expensive) adapter when I couldn't come up with a suitable, high-quality, alternative of my own...