Replace old Cold Light head with LED light source?

[Willie]

Am using an older 5x7 Beseler enlarger that came from the factory with a cold light head. It is old and the light is feeble.

Anyone with knowledge or experience in what kind of LED lighting might work to put in its place?

Doesn't have to specifically fit in the old head as can modify to make it a bit larger if needed. Quick on and off is more important - as if I were using the condenser head with light bulb.

Am asking so I don't make the normal mistakes and end up doing it three or four times before I get it to work.

[Larry Gebhardt]

Not knowing the cold light head details this may be easy or not. My first LED head was build on an old Omega E3 by pulling the internals from the cold light head and replacing them with a constant current driver and 12 high power (3W) Cree XPG LEDs on a star. These were screwed to a sheet of 1/4" aluminum for support and a heat sink. A piece of opaque plexiglass provides diffusion. The hardest part was getting the LEDs arranged to provide even light. A 3x4 grid evenly spaced resulted in a bit of a hot spot and I ended up making a pencil mask to dim the center. Live and learn.

I used a Meanwell LPC-60 driver. Turns on very quickly - seems much faster than an incandescent bulb takes to heat to full brightness - but I haven't tried to time the two. The spec sheet indicates a 500ms setup and 120ms rise time but the light seems to come on simultaneously to the relay in my timer closing.

[Keith Pitman]

This post might be helpful: https://www.largeformatphotography.info/forum/showthread.php?139056-LED-Diffusion-Lighthead-for-Omega-D5

[Willie]

Keith, thank you for the link. Missed it when I initially did a search. Probably didn't put in the right terms.

Appears as if it may be something I can do or get done.

[Tin Can]

Perhaps the best made now?

https://heilandelectronic.de/led_kaltlicht/lang:en

[Daniel Unkefer]

https://live.staticflickr.com/65535/48127137443_f38ef8bae9_z.jpg (https://flic.kr/p/2gjQaeM)LED Lighthead v1 BottomAssembly (https://flic.kr/p/2gjQaeM) by Nokton48 (https://www.flickr.com/photos/18134483@N04/), on Flickr

https://live.staticflickr.com/65535/48127140158_2e6d6a0cc6_z.jpg (https://flic.kr/p/2gjQb3A)LED Lighthead Strips TopAssembly (https://flic.kr/p/2gjQb3A) by Nokton48 (https://www.flickr.com/photos/18134483@N04/), on Flickr

Looks doable to me. Total cost around 300 Bucks?

[jose angel]

I would advice to made something like Daniel`s setup. Easy and effective. I would also place the LED lamps alternatively, instead of making a square grill.
You should check the diffuser to LED stage distance, for full power and to avoid hot spots, so design it thinking on a possible height positions.
My only issue with this design is the lack of power, you must find a really powerful LED strip. Cheap supermarket ones may not work. So make the LED chassis or plate designed to be easily upgraded or replaceable, or maybe, ready to be used with differently powered LED plates (instead of a more complex dimmable system).
My problem with much stronger LED units is the hot spot, as Larry experienced. Strong LED units work better on condenser head types.
BTW, the filter drawer is nice, but not a must IMHO. I have it but rarely use it on larger formats. I prefer a good under-the-lens system, faster and way more practical (e.g., for split printing).

[Daniel Unkefer]

Sheets of Rosco Gel apparently work well for split-filtering VC paper. Not expensive at all at B&H