Super Chromega D Dichroic II

[Donald Qualls]

I've been working on combining the color head that came with the D5 I bought last spring, with the frame for my (much less worn and more familiar) D2. Before disassembling the D2, I've been making sure the Super Chromega D Dichroic II head works.

It doesn't.

The fan powers up as soon as I switch on the power supply (as I gather it should); the panel light operates when I move the switch behind the color filter dials. The three filters all move with the dials, and move out of the way when I switch the side lever to "WHITE" -- though the neutral filter is missing from the plate that moves in when I set that lever to "LOW", so I'm on "HIGH" all the time. I've tested my Gralab 525 digital timer, and once I found the right combination of modes, it switches power to the Safelight and Enlarger outputs correctly (tested both outlets individually with my safelight -- see why below).

Unfortunately, even after repairing the melted wire nut on one of the wires leading to the main lamp and verifying the new-looking lamp has about 7 ohms across the filament (as opposed to an open circuit if it were burned out), I'm getting no main lamp start.

Still to do, when I replace my multimeter (which failed today, by one of the probes coming off the wire -- and I can't find the spare probe I thought I had) is to check that the 24V output on the power supply is actually delivering power. Of the 7 wires in the cable between supply and head, I should have one pair at 24V (for the main lamp), one at 120V (for the panel lamp), and another pair at 120V for the fan motor, I think (why separate that from the panel lamp, I don't know).

It's not clear from the manual whether the lamp is operated on AC or DC -- DC might provide slightly better lamp life or brightness, but AC would simplify the power supply; all that would be needed is a suitable transformer powered by the "Timer In" connection on the power supply.

Is 24V output a known problem with these, or is this more likely to be a bad wire connection at the plug or an issue with my extension cord from the timer not making contact? Obviously, this worked at some point, else it wouldn't have had power the melt the wire nut -- but I have no way to know if that was with this power supply.

EDIT: And now it does. I went back and rechecked the power cord from timer to timer input on the power supply -- I'd had to trim the extension cord's outlet a little to get it in (the receptacle is a circular opening with the prongs of a standard 120V plug inside -- vaguely similar to one generation of Bosch circular saws from ten years or so ago) -- and when I pulled the cord end out of it, I could see the plastic had been deformed by the metal receptacle. I applied a sharp blade to trim down the plastic a little (carefully, not to get close to the conductors inside) and reinserted it, and it went in a good quarter inch deeper than before. Reconnected everything, et voila, I have light!

Now, does anyone know the correct value of neutral density that should go in the "low" paddle, for those times when I need a longer exposure?

Also, is there any sensible reason, when I get a spare projection lamp for this beast, to get the "high lumen" with the 50 hour rated life, vs. the "long life" of the same wattage, six times the rated life -- and about 2% higher output? I presume this is just a newer technology version of the same lamp assembly...

 

[DREW WILEY]

The power supply is supposed to cut down max voltage and light output just a little in order to prolong bulb life. The actual life of bulbs depends on several things - the cooling fan must still work well, the bulb socket should be corrosion-free, and then, the quality of the specific brand is very important. Junk made-in-China cheapo bulbs will have a dramatically shorter lifespan than high quality ones actually made in Japan, Germany, or the US. The brand name itself might not tell you, because some companies offer both; you have to check the specifics, though one generally gets what they pay for. A junk bulb might pop in a week, a good one maybe after ten years of use - spoken from actual experience.
The "low" setting is approximately 2 stops less.

 

[ic-racer]

From the description is reads as if you have the standard D power supply, which is just a 'transformer in a box' which steps 120V down to 24V AC for your lamp.
If you see the schematic you can probably figure it out.

 

[ic-racer]

The density filter is like a strainer or screen. It is metal. You can see it here on this "D" head I repaired a while ago.

 

[DREW WILEY]

That concept is called a scrim in studio lighting.

 

[ic-racer]

You probably already figured out that you need to keep exact notes of the positions of the washers and springs when disassembling the filter mechanism. One can almost bet it is buggered up if someone has been in there before.

 

[ic-racer]

That concept is called a scrim in studio lighting.

Yes, that is it. Also, on the Durst it is more of a 'non-diffracting' aperture which is adjustable.

 

[ic-racer]

I have not had any trouble finding halogen lamps, so I only have a few spares, expecting I'll just get the off the internet if they burn out. In fact 3 tiny lamps for my Philips PCS 150 ADDITIVE system were only a few mouse clicks away last month when I ordered 3 spares. Those might be considered 'rare' because they are not the usual MR16 base.

I started a thread about 10 years ago about converting a "D" Dichroic II head to 120v with a 120v MR16 lamp and no power supply.

 

[Donald Qualls]

From the description is reads as if you have the standard D power supply, which is just a 'transformer in a box' which steps 120V down to 24V AC for your lamp.
If you see the schematic you can probably figure it out.

Yep, that's what I've got -- a heavy, simple-looking brick with a switch on the front, cord, 120V receptacle (for timer), 120V plug-in-a-hole (for timer in), and the 7-blade connector to the head.

I have not had any trouble finding halogen lamps, so I only have a few spares, expecting I'll just get the off the internet if they burn out. In fact 3 tiny lamps for my Philips PCS 150 ADDITIVE system were only a few mouse clicks away last month when I ordered 3 spares. Those might be considered 'rare' because they are not the usual MR16 base.

I started a thread about 10 years ago about converting a "D" Dichroic II head to 120v with a 120v MR16 lamp and no power supply.

The 24V lamp doesn't appear to be hard to find or excessively expensive; I'll probably just order a spare on payday. Converting seems like it should be electrically trivial -- replace socket with correct type for the new lamp, replace 7-wire cord with two cords (so the panel lamp and fan are independent of the timer) and maintain proper case ground. Getting in there would be the challenge, but I work on more complex stuff than this every day.

For the LOW scrim, then, it looks like I'm after an approximate 25% porosity metal mesh; I think I can mount a replacement by just removing the lamp and gluing with high temperature silicone -- or if not, as noted above, this isn't complex compared to rotary hammers and the parts are big and easy to handle compared to the tiny air tools I've been estimating the past couple weeks at work. The filters appear to work correctly as it stands (right colors move with the right wheels, cut into the light, which gets evened out in the mixing chamber), so if I mount the scrim from the bulb side, it shouldn't cause problems.

 

[ic-racer]

You might find an original scrim replacement on ebay. Otherwise, I'd consider a few layers of metal screen or, if you have a punch and a drill and graph paper, make one like the original from a piece of aluminum.
I'd probably go with some screen, as I think the original scrim is too limiting for B&W. Seems to be designed for making 4x5" color prints to match 8x10" prints at the same baseboard luminosity.

 

[Donald Qualls]

You might find an original scrim replacement on ebay. Otherwise, I'd consider a few layers of metal screen or, if you have a punch and a drill and graph paper, make one like the original from a piece of aluminum.
I'd probably go with some screen, as I think the original scrim is too limiting for B&W. Seems to be designed for making 4x5" color prints to match 8x10" prints at the same baseboard luminosity.

For B&W, I don't much care if I need a longer exposure -- in fact, longer than 10 seconds is highly preferred (though my timer does work in tenths if needed). I think I'll still look for 25% (= 2 stops). Good thought on checking eBay (and possibly that online parts dealer) for an original type replacement. I agree, 4x5 test print, then get the same exposure for 8x10 (without having to stop down the aperture further) seems like a sensible reason for the thing to exist in the first place.

BTW, have folks found a need (for color printing) to cover the front panel (HIGH, LOW, WHITE) display? It had black masking tape over it when I got the head, but the light shield was mis-installed (blocking the fan, rather than covering the panel light), so it might have had main light leaking there, which would be enough to fog paper, I'd think.

 

[ic-racer]

It has been a while, but as I recall there was a switch to turn to display off.

 

[Donald Qualls]

@ic-racer You're correct, I have that switch, and it works. So, no sensible reason to need the display covered, now that I've corrected main lamp light leaking from it.

 

[ellipticalquiet]

I'm getting no main lamp start.

transformer in a box'

Hey folks, I am having a similar sort of problem with my 412-021 voltage regulator. The fan and panel bulb seem to be receiving 120v AC, but none of the crimp terminals coming out of the wire seem to be transmitting 24v AC. I am a little green at this but I am more than willing to follow & learn if one of you folks would be willing to teach me how I might salvage this thing.

 

[Donald Qualls]

Hey folks, I am having a similar sort of problem with my 412-021 voltage regulator. The fan and panel bulb seem to be receiving 120v AC, but none of the crimp terminals coming out of the wire seem to be transmitting 24v AC. I am a little green at this but I am more than willing to follow & learn if one of you folks would be willing to teach me how I might salvage this thing.

Assuming you're supplying 120V to the "Timer In" connection on the back of the power supply, you should get 24V out between two of the receptacles in the 7-blade socket on the back (not sure which pair, but the wiring diagram that was linked here recently might have the pinout). If you are, there may be a problem with the cable from the power supply to the head; if not, there's an issue with wiring or the secondary transformer inside the power supply.

 

[ellipticalquiet]

if not, there's an issue with wiring or the secondary transformer inside the power supply.

This seems most plausible. My multi-meter tells me that there are about 120V AC (actual measure is 123-124V, Which is close enough I'm guessing) coming from the "To Timer" socket. Only the middle pair of the three sets of pairs on the inside of the voltage regulator is carrying voltage, and that pair is carrying 120V AC (123V actually). Where to go from here? Do you figure I could find what's causing the other wires not to carry charge?

 

[Donald Qualls]

You'll need to check continuity from the various blades on the plug to the end points inside the head. You know which two carry the 120V; there should be two more that have continuity to the lamp socket (or at least its wires); the corresponding sockets should have 24V AC between them.

 

[ellipticalquiet]

You'll need to check continuity from the various blades on the plug to the end points inside the head.

I think, actually, I've figured it out. I had to read what you said a little more carefully. There had to be 120v AC coming into the "timer IN" socket! The timer that came with this unit was the problem. Somewhere there was discontinuity in the timer; where that actually is however, I will have to test a little more to figure it out. Luckily I already have a Gralab 300 timer sitting around for use with the condenser head that I usually print with, and it outputs 120v AC. I plugged it in and viola! 25V AC coming to one of the female crimp sockets meant to go inside the head. Seemingly the other crimp socket meant to be giving me 120v AC for the panel bulb is not giving me that anymore, but that I care about significantly less.
Now, a few questions: 1) Is the timer salvageable, has anyone got a schematic for that?;
2) How awful is one volt over? I have those SoLux bulbs for which one volt over makes for a color temperature change which is not insignificant.; and
3) Unrelated, what is the purpose of the u-shaped piece of plastic in my mixing chamber? When I opened the chamber it seemed to just be freely floating around in there, what is the proper orientation for it?

 

[Donald Qualls]

The voltage will drop a little under load, I wouldn't worry about 25V reading on the 24V nominal circuit. Color temperature change won't matter for B&W, and you'll just compensate filters if you print color.

 

[oliton]

As I am about to embarque into the restauration of a friend's D2, would a charitable soul be able to share with me the enlarger's manual and/or schematics? The unit I will take care of has been stored for a long time in an attic, half disassembled. I need to be able to check if all the parts are there and if the owner will have to order some stuff.
Any help would be really appreciated.