After years of thought and slow construction, my modified Beseler CB-7 (changed from the negative platform up) is newly mounted with a 10x12" LED light source of my own design. For those considering their own, here's what you might expect.
16 green and 17 royal blue, 1 amp Cree LEDs use about 35 watts. Contrast control is a simple knob that shifts from all green to all blue; half and half in the middle. It is 2 stops brighter than my 12x12" Aristo V54 was and gives a slightly broader contrast range on both ends than the standard #00 to #5 filters (on Ilford MG Fiber Classic). Unit plugs into a standard timer. There is no warm up or tail-off of the light. Evenness appears to be very good, but this required careful design of the diffusers.
None of the parts for the build is particularly expensive, just lots of them. LEDs were $4/ea. The other items nickel and dime you to death. Time is the biggest expense. My drive electronics are all analog, through-hole style, so that I could build them by hand. If one isn't familiar with op amps, current sources, FETs, and soldering, then this should not be attempted.
If I were to start again, I would seriously consider using 'super bright' LED tapes of royal blue and green. Power each with an adjustable current supply that is controlled by a potentiometer. Gang the "pots" on a single shaft such that as one increases, the other decreases.
Besides not having to fiddle with filters, the biggest surprise is how much difference just a tenth of point in contrast can make in a print.
If you're designing your own and would like to correspond, my email address is ejwoodburyatgmaildotcom. No PMs, please.
Happy printing in the new year.
Bookmarks