Durst 138S Replacement Bubs

[Graybeard]

I have a new (to me) Durst 138S with a B&W condensor head on the way to me. There is quite a bit of pleasant anticipation on my part; first decent enlarger that I had (still have, in fact) was/is a Durst 606 whose purchase price represented an entire week's pay for me from the summer job that I had 47 years ago. It is time for me to consider which replacement bulbs I'll need for my second jewel from Bolzano.

What bulbs are currently available for use in the B&W head with the Latico 240 condensors for 5x7? I'm aware that this question has been discussed here in the past but sources of the bulbs and availability of specific part numbers seem change frequently.

GE sells a 100W opal bulb (part #G40, 4 3/4" in diameter) that I've found to be useable with a 5x7 Elwood (on a socket extender). This bulb is available nearly everywhere and even has the label down near the lamp base like a PH series enlarger bulb. At about $5 each, this would seem to be a sensible one to try. Lowe's offers a Sylvania 150W bulb of similar physical dimensions.

What bulbs are other Durst 138 owners using and where do you find them?

[ic-racer]

One just sold on ebay yesterday. 10 bids to about $137 USD.

That bulb you are showing looks nice but maybe 100w is not enough. One thing I had always thought of is to take a glass cutter and remove the top part of that bulb your are showing and rig it up in front of the more common 250w smaller enlarger bulbs.

Another thing that might be worthwhile is using diffuser material somewhere between the bulb and the negative and again see if you can get the $5 PH213 250W lamp to create an even field.

[Michael Clark]

I think the Idea is a large diffuse light source bulb,the original bulbs are like 5" or so in diameter.I was thinking if a 200 or 300 watt smaller bulb could be used if a larger frosted glass lamp could be inserted in-front of the smaller bulb,thus spreading out its light more uniformly. Could be a cheap fix.

Mike

[Donald Miller]

I still have two of the original Thorn bulbs that I am not using. One is 300 watts and the second is 500 watts. I personally converted my 138S to more of a point light source by designing a new reflector and incorporating a 1200 watt lamp. This involved quite a bit of trial and error to arrive at a new lamp placement and reflector design and installation. This necessitated a number of other changes among them was the installation of a sizeable cooling fan. Without the cooling fan the lamp that I use will melt glass. If I were redoing this modification today I would opt for a 600 watt lamp. I have converted other enlargers with the lower wattage lamp (600-650 watt) and they worked out very well.

With the point lamp, one can use diffusion material in the internal filter drawer to create varying degrees of diffusion. I would think that diffusion used in conjunction with a smaller diffuse lamp envelope may work better than without diffusion. The point lamp that I use gives me results more in keeping with those that Brett Weston achieved with his point source 138...contrast is enhanced and sharpness is without equal.

Jensen Optical had, at one time, a conversion kit for these older enlargers. I don't know if Jens still offers these or not.

In my experience the 212/213 lamps that have a smaller envelope that some have used are too low wattage for what I needed.

[Len Middleton]

Graybeard,

To address the issue of no new replacement bulbs being available, Jensen Optical has designed a new system to address that problem: http://www.durst-pro-usa.com/lamp_kit.htm

To get around the issue of the clear bulb they use, (essentially a point source with a large filament), they provide a heat filter and opal glass. On my V184 condenser head there is a metal bracket on the lamp side of the divider that supports the first condensor before the mirrors. That is where one could install the heat filter and opal glass.

From the notes on the little bit of research I have done thus far:

1. Current large Thorn bulbs and replacements have not been made in some time (over 25 years?), and are available only on secondary market and rarely found, and expensive if seller knows of rarity. Bulbs have unusual envelope sort of a cross between a standard “A” and “G”. Diameter is approx. 4-1/4” (e.g. G34 or A34), and MOL is approx. 7-3/8”.

2. Larger photo bulbs, not generally available and expensive ($200 to $300 at donsbulbs.com) when available. At 300W or greater, a cooling blower is recommended.
a. PH/300 ANSI – 150W, 3100⁰K, PS30 glass, C9 filament, MOL 8.19”, 100 hours, 3300 lumens
b. PH/301 ANSI – 300W, 3150⁰K, PS30 glass, C9 filament, MOL 8.19”, 100 hours, 6650 lumens
c. PH/302 ANSI – 500W, 3200⁰K, PS30 glass, C9 filament, MOL 8.19”, 100 hours, 11000 lumens

3. Need to research and experiment on replacement lamps. The use of an opal glass diffusion panel before the first condenser in the enlarger will mitigate the impact of a smaller light source. Whether it will be enough for even illumination remains the question. Potential additional solutions include:
a. Lamps with large envelopes (e.g. G40), but variation between lamps (spectrum) may be high.
b. Halogen lamps with an E26 base, so no modification to the enlarger is required.
c. Halogen lamps with another style base, but with an adapter that could handle the heat involved.

Anyways, it will be something I will need to address, but having two 100w Thorn bulbs and a PH/302 500w will give me some respite once I get the enalrger set up.

Hope the information is helpful to you,

Len

[Michael Clark]

Donald,with the 600 650 watt lamp did you have to use a cooling fan.

[Cesar Barreto]

I've been using 200w Chiyoda bulbs for some time and still have 2 or 3 spare, but don't know yet what to do when they're gone.
Those bulbs are kind of flat and have about 8cm diameter and I managed to use it with both 138s and L 1000, although a piece of difuser may help sometimes.
Actually, I was expecting a solution using Led arrays or something alike, but it seems only trials have been made and nothing came to market so far.
Have anyone had success using this method?

[Donald Miller]

Donald,with the 600 650 watt lamp did you have to use a cooling fan.

Yes, I did. Although the fan I used with the 650 watt lamp was a lower CFM than my fan on the 1200 watt lamp.

[ic-racer]

One just sold on ebay yesterday. 10 bids to about $137 USD.

I forgot to mention that things could be worse. I recently got two spare bulbs for my CLS2000 and each bulb was over DOUBLE that price. Plus, these bulbs don't come with the dichroic reflector. That is an additional $1800 if you need it.

[Graybeard]

Thank you all for the helpful comments.

I'll probably begin by trying the 150W Sylvania G40 bulb and see if the source intensity is adequate for me.

With my Elwood 5x7, the GE G40 100W bulb gave useful exposures of 20-30 seconds at f8 when I enlarged a normal density 5x7 negative to 11x14 using a #3 Ilford Multigrade filter. I would expect quite a bit of light loss to have occured with the diffusion plate in the Elwood. The condensor system of the Durst should be more efficient and have less transmission light loss. The 150W G40 bulb may prove just adequate; given the low cost of this bulb, it won't be an expensive experiment.

If not, there are plenty of other ideas here for me to try.