Replace the Duka osram bulb by led

[czygeorge]

Well unsurprisingly the bulb of my duka 10 was done after I accidentally forgot to turn it off for three days.

I tried to contact the former agent of osram sodium lamp in my country and sure they have no stock after its discontinuing（na 10 fl，Actually it was used for stress gauge）

Finally after many time of failure tried，I replaced it by a 5w led lamp bead(which is really small,the light length is 590-595nm,I think you can find one common or better in your country too),What you need to do is to remove all the structure served for original lamp(lamp holder，transformer in the bottom of the safelight),only keep the light strength control system,It's not easy to remove those screws because those German has put glue in it...

Than you have to replace the the original circuit by a battery support(Since the lamp was too small there's no reason to charge it by 220/110v AC),The lamp I bought need a 2.4v battery.And connect it to the lamp and the original switch in the safelight(You can just connect to the wire was connected the former sodium light as it was connected to the switch already).Last step was glue the lamp to a heat dissipation aluminum(which was small enough to fit the lamp hold space),cus without it the lamp wavelength would be longer when it was overheated.

I did coin test of my ra4 paper and did enlarging with the new led safelight turning on,looks like three to four minutes would do no influence to the paper(haven't test longer),also turn it on for 90mins the light was still steady but not meet overheat problem.

Hope this could help those same safelight owner with bulb problem.Forgive my poor english since I've never use it for a long time

 

[koraks]

That's a very hopeful result! AFAIK a Duka 10 is pretty dim - how much can you actually see under this safelight?

I've done some testing with actually useful safelight levels, i.e. levels that you can conveniently cut paper with etc., and the results were not very encouraging.

I did coin test of my ra4 paper

Did you test for color shifts? In my testing I observed severe color shifts in the actual image with safelight exposures that did not yet produce any visible density in the paper whites.

 

[czygeorge]

That's a very hopeful result! AFAIK a Duka 10 is pretty dim - how much can you actually see under this safelight?

I've done some testing with actually useful safelight levels, i.e. levels that you can conveniently cut paper with etc., and the results were not very encouraging.



Did you test for color shifts? In my testing I observed severe color shifts in the actual image with safelight exposures that did not yet produce any visible density in the paper whites.

Yes it is really dark you need to set it to the lowest level,I put it for meter away on the top of book shelve and aim to ceiling.

Only can I see something when i let my eyes adapt it for thirty secs.
And with this level of light strength the color shift haven't happened to my work

Cut paper is really a frustrated job I'm used to do it with a paper box used for those fuji minilab machine.I cut 10' and 30' and use my hand's length to estimate if I pulled enough paper out and cut it.

 

[koraks]

use my hand's length to estimate if I pulled enough paper out and cut it.

That sounds like a fine way of doing it.
I usually tape a piece of wood to the cutting table and use that as a stop. It's a little more accurate than your method, I suspect, but there's still a few mm's of variation between individual sheets. Doesn't bother me; just cut a little longer than necessary and/or print a little smaller to ensure the prints always fit.

 

[czygeorge]

That sounds like a fine way of doing it.
I usually tape a piece of wood to the cutting table and use that as a stop. It's a little more accurate than your method, I suspect, but there's still a few mm's of variation between individual sheets. Doesn't bother me; just cut a little longer than necessary and/or print a little smaller to ensure the prints always fit.

yes！！Rough but save a lot of money though

 

[koraks]

Exactly; even if you waste a little paper because your sheets are larger than necessary, it's a whole lot cheaper than buying cut-size.