Halogen Enlarger lights

hoffy

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Howdy,

I am currently using a small Durst M305 with Colour head. I am not sure if this is standard, but it uses a 12V Halogen globe, powered by a dedicated transformer.

Tonight, I noticed a couple of times that the light was flickering ever so slightly. It wasn't all the time, but I did stuff up 1 print due to it.

Would this suggest that the globe is on the way out? Would these just be standard down lamps? Should I be heating up the globe before making critical exposures?

Cheers
 

Ian Grant

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More likely to be a power supply problem, halogen bulbs tend to just suddenly blow rather than the flicker you occasionally get with normal hosehold bulbs.

No need to warm up these lamps, they reach a paek very quickly.

Ian
 

Thomas Wilson

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hoffy said:
OK, no probs.

Do you know whether I can use a normal DC power supply? I have a regulated variable unit that I use for other hobbies (Slot car racing).
Click to expand...

Yes, 12 VDC is 12 VDC, regardless of the source. The only variable is the capacity (usually in watts) of the 12 VDC power supply.

If your lamp is rated at 100 watts @ 12 VDC, make sure your power supply can deliver at least that much. 125% of load should be a minimum.

Note, you may use a 12VDC power supply with a much higher capacity than will be needed as the lamp will only draw what it requires. In other words, you wont blow a 12 VDC 100 watt lamp by energizing it with a 12 VDC 300 watt power supply.
 

MPandolfo

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Thomas is right, but usually power supplies are rated in Amps rather than Watts. In this case, you obtain the Ampere rating by dividing Watt/Volts, i.e. 100/12=8.4 Amp, so you need at least an 8.4 Amp. supply. If more, doesn't hurt. The lamp is originally meant to be driven by AC current, but DC will work OK. I suggest you use a common domestic halogen lamp 12V transformer, it's far cheaper than a DC supply and will work equally well if not better.

That said, I don't think you have a power supply problem. Your description fits better a wiring/contact problem. Check all the cables, sockets, terminals, etc. in the low voltage circuit of the enlarger (the 12V side). As currents are very high there (yes, 8 Amps is a pretty high current) is very likely that you have a sparking contact. If this is the case and you don't fix it soon, the damage will keep growing and you will end up with a very smelly darkroom, if not a small fire.
 

Larry.Manuel

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I've noticed halogen 50w screw-base pot-light and track-light bulbs often vibrate in houses as people walk around - with heavy feet. The filament vibration looks like a flickering effect. It might be the same with your enlarger bulb. If yours is truly flickering, I'd suspect a poor connection somewhere [especially in the bulb socket due to heat-corrosion]. Low-voltage circuits are susceptible to that.
 

pentaxuser

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My experience tends to contradict that of Ian Grant. I have had a 100W bulb fitted to a Durst 605 and before it went it did seem to flicker a bit and yes it does play havoc with prints especially RA4. However another cause in my case was that the power to the twin prongs on the back of the lamp is via a ceramic holder and apparently arcing can occur inside the holder which builds up a form of resistance. Some say that the ceramic holder should be renewed every so often but others say that a small round jeweller's file should be pushed into the two holes and the holes cleaned. If you haven't got such a file then a large sewing needle will do if you scrap the inside of the holes to clean them.

Get a new bulb and try it. If the problem goes away then the bulb is likely to be on its way out. If there is still signs of flickering then the ceramic holder might need replacing or cleaning.

In all of this of course I am assuming that there aren't any loose connections. That might be the first check required

pentaxuser

pentaxuser
 

Ian Grant

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Definitely clean the contacts every few year, my De Vere 5108 was blowing a bulb regularly, always th same one of the four (far more expensive) that was down to oxidation on the contacts, I use 1200 grit Wet & Dry.

Don't you go contradicting me Sometime when I'm in the UK we'll have to meet up again and have a better chat (luckily I can easily understand his Daventry accent ).

It is more likely to be a contact or voltage problem, the filaments in Tungsten Halide bulbs are robust but they operate at very high temperatures, they give a constant output through out their life, no colour shift etc, but a spike in voltage or arcing kills them.

Ian
 

paul_c5x4

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Not wanting to appear to be contradicting Ian, but.... Did some enlargements recently and couldn't get the contrast I was after. A few days prior, grade 3 on VC paper looked crisp, but not this time round. Changed the bulb and started getting the prints the way I wanted - Concluded that the bulb was fading or had a colour shift and on it's last legs.
 

Ian Grant

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paul_c5x4 said:
Not wanting to appear to be contradicting Ian,
Click to expand...

These bulbs can & do change over time, my main use was outside the darkroom, we used them in stores, & I also used them in my office/study. I've seen the coated part of the reflector oxidise & lose reflectance long before the bulb blows.

What's always surprised me is that in Durst enlargers they last well, in 30+ years I've not bought more than 5 or 6, probably less. I know my spare bulb is 20 years old

Of course some manufacturers bulbs may be better than others, but my enlarger bulbs in the Durst have always lasted extremely well.

Ian
 

Thomas Wilson

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Ian is correct, probably on all points. The biggest contributor to lamp failure is the jolt it receives when energized, not the burn hours. The finer lamp-house power supplies ramp-up and then ramp down voltage (very quickly) when switched on and off, minimizing the jolt to the filament.

All lamps will lose luminescence and experience color shifts as they age.

Mean Well is a pretty good manufacturer of low voltage step down transformers. I bought this one to power my Super Chromega Dichroic lamp-house. It arrived a couple of days before I located two mint Chromegtrols. for which I paid $25.00.

I went with the Chromegatrol.
 
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MattKing

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hoffy

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OK, looks like I was a bit wrong. Don't know where I got M305 from (it was late and I was tired). Its a M301 with a CLS35 colour head. According to this site, I need a EKG:

http://www.replacementlightbulbs.com/lampscrossreferenced.html.

Does anyone know if this is the correct part?

Now will be the fun part in finding one!

Cheers
 
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MattKing

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That bulb is an 80 Watt 19 volt bulb, which doesn't seem to match the rest of the information in your thread.

Any chance that the voltage regulator is the wrong one for your enlarger?

Matt

P.S. the EKG bulb does seem to be the one indicated for that colour head
 

ic-racer

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A few things I have noticed. If the power supply regulates the AC voltage using pulse width modulation and a triac, a dirty contact can cause it to ramp up the voltage and when it arcs across the contacts the bulb can blow.

I also had a power supply that produced a stocastic unsteady voltage, irrespective of the above problem. After a complete rebuild, its voltage output was rock solid. (there was a url link here which no longer exists)
 
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hoffy

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OK, just a quick followup. I went to the local lighting supplier. What I have found is that these kind of lamps are becoming harder to find! They have suggested a new lamp that matches the Power supply, moreso then the enlarger. The only issue that may become apparent is focussing, but considering that to focus, the whole lens moves, this should be overcome.

I'll find out tonight I suppose!
 
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