LPL 6700 with no transformer - ideas?

[davidbrown57]

Good evening, I have just bought a large darkroom sink and with the sink came an LPL 6700 enlarger. But it does not have a transformer. It has a 12v 100w bulb. What is the most cost effective way to connect it to a transformer and timer? Could I just swap the bulb for a 240v LED? What about a normal light 12v transformer - would that work. Any other suggestions very welcome. I am not adverse to a bit of DIY electrics and can use a soldering iron. Many thanks in anticipation of your help

[glen_h]

This one:

http://www.khbphotografix.com/LPL/LPL6700Dichro.htm

says that it should have an 82V halogen lamp.

As far as I know, 82V is designed for a regulator run on 120V.

 

For actual 12V, there are many power supplies designed for PCs that could

be adapted for an enlarger.  The smaller ones, for 1U rack mount boxes,

might be 250W or so.  They aren't designed to put full power at 12V,

but some should be able to do 100W.

[rodeo_joe1]

The condenser head version will take a standard bulb and needs no transformer. 

My LPL C7700 uses a 12 volt 100W dichroic-reflector bulb. I'm pretty sure the dichroic colour head version 6700 uses the same bulb and transformer. 

Unless you're doing colour, there's no real need for a voltage-stabilised transformer, and nowadays you can get tiny domestic 12v switch-mode PSUs for low voltage ceiling lights. The only modification needed would be to cut the proprietry plug off the enlarger cable and wire it into one of those little white 12 volt supplies. 

The huge and heavy black box that came with LPL enlargers was designed before modern switch-mode supplies became cheap and commonplace. No need for such a monster these days. Just make sure you get a supply with at least a 100 watt total load capacity. 

Edited February 21, 2023 by rodeo_joe1

[glen_h]

11 hours ago, rodeo_joe1 said:

The condenser head version will take a standard bulb and needs no transformer. 

My LPL C7700 uses a 12 volt 100W dichroic-reflector bulb. I'm pretty sure the dichroic colour head version 6700 uses the same bulb and transformer. 

 (snip)

This one:

http://www.khbphotografix.com/LPL/LPL7700series.htm

does say 12V 100W for the 7700.  The one I linked above says 82V for the 6600.

 

I do remember that 82V is not rare for projector lamps. 

 

But yes, little switching power supplies are easy to find. 

I am more used to computer power supplies, and suspect that they are

a little more reliable.  I bought one of these:

 

https://www.amazon.com/dp/B0B92S3QX1

 

for an actual computer not so long ago.

(Actually, it is NAS, Network Attached Storage, which is a computer

with four disk drives, two gigabit Ethernet ports, and no keyboard or

monitor port.)

 

That one is $35, and 240W at 12V, and also nice and small.

(It fits in a 1U case, and is 40.5mm (less than 2in) tall.)

 

82V switching power supplies will be harder to find.

 

 

 

[rodeo_joe1]

What idiot thought a bulb requiring 82 volts was a good idea!? 

[glen_h]

27 minutes ago, rodeo_joe1 said:

What idiot thought a bulb requiring 82 volts was a good idea!? 

Years ago when I was looking at projectors, and bought the Kodak 760H,

I also looked at the 760HK.  That is the selectable voltage version.

(Though without any plans to move to Europe.)

 

Looking at:

http://www.khbphotografix.com/LPL/LPL6700Dichro.htm

at the bottom of the page, it indicates the 82V lamp for

US and Canada, and the 12V lamp, presumably, for other

countries.

 

The HK cost a little more, and I always wondered later, if the bulbs

last longer. I don't know the power supply that Kodak uses for those

projectors, though. 

Definitely it is harder to make incandescent lamps at higher voltage,

and especially at 240V.  It might be a switchable series inductor,

or some other type of regulator. 

 

As you note, we now have nice switching power supplies that

they didn't have so many years ago.

 

There use to be:

https://en.wikipedia.org/wiki/Voltage_regulator#Constant-voltage_transformer

saturable reactor transformers that have close to constant output voltage.

(Though might be frequency sensitive.)

 

In any case, there are some interesting things you can do with an 82V bulb.

[glen_h]

It seems that the 60Hz Kodak Ektagraphic projectors

(industrial strength versions of the Carousel projectors)

use 82V bulbs:

kodak_ektagraphic_iii_a_kka_ja_ats_am_amt_jamt_b_br_e_e_plus_slide_j-e_plus_kke_plus.pdf

(I never knew that Korea is 60Hz 220V before!)

 

They use windings on the fan motor to get the lamp voltage.

The manual doesn't explain how they do Japan's 100V or Korea's 220V, though,

but I suspect also with fan motor windings.

 

I don't know about Kodak 50Hz projectors.

[davidbrown57]

Its just for black and white - do you think I could put a 240v LED in it?

 

[glen_h]

16 hours ago, davidbrown57 said:

Its just for black and white - do you think I could put a 240v LED in it?

 

There are two versions of the dichroic enlarger, one for color and the other for

variable contrast black and white paper.  The 6600 is the condenser version

using lamps with regular lamp sockets. 

 

The dichroic versions use dichroic lamps, it seems the ESJ

https://www.bhphotovideo.com/c/product/610350-REG/Impact_ESJ_ESJ_Lamp_85W_82V.html

for the US version.  I will guess that your uses a similar shaped bulb but 12V.

The dichroic reflectors for lamps don't reflect IR, which keeps the negative cooler.

(Or slide for slide projectors.)  That is separate from the dichroic filters for color

balance or B&W contrast.  The lamp and reflector come as one piece.

 

It would be interesting if someone made an LED in the same shape,

but be used in its place.  It should have the same reflector, same light

output distribution, and same color temperature.

[glen_h]

It looks like the 12V version is EFP.    Some seem to sell

them for about USD 7.00 others closer to USD 60.00.

 

 

They look similar to the ESJ, but I don't know if they fit in the same socket. 

It does seem that some dichroic reflector lamps have an LED replacement.

[rodeo_joe1]

17 hours ago, davidbrown57 said:

Its just for black and white - do you think I could put a 240v LED in it?

What bulb does it have at the moment? Because the easiest route is to use the same bulb holder and get a power supply to suit. 

I take it you're in the UK if you're talking about 240 volt mains? 

In which case the enlarger probably uses a 12v bi-pin dichroic reflector halogen bulb, and it's not going to be easy to fit a powerful enough LED into the same space. 

A 100w equivalent domestic LED bulb would be perfectly OK as far as light output is concerned. There just might not be enough room in the lamp-house for it. 

[glen_h]

Should look like this:

https://www.bhphotovideo.com/c/product/822392-REG/Impact_EFP_EFP_Lamp_100W_12V.html

[rodeo_joe1]

42 minutes ago, glen_h said:

It would be interesting if someone made an LED in the same shape,

Not easy. I looked at adapting a LED module to my Durst L1000 5x4 enlarger. It takes a 24V 250 watt(!) dichroic reflector bulb. Apart from costing a small fortune to replace, that bugger puts out a lot of heat and needs a vibration-inducing fan to cool it. So a LED would be a far better option. 

I figured a 50 watt LED module would put out about the same amount of light.... but (1) a 50 watt LED chip needs a sizeable heatsink and, albeit smaller, fan. (2) The heatsink and fan won't fit in the same space as the dichroic bulb. (3) The LED module needs 36 volts DC to drive it. (4) The LED module doesn't have a focused light beam like the dichroic bulb. 

The PSU is a trivial issue, but the overall bulk of the LED module + heatsink + fan - which all have to be thermally coupled - is the real stumbling block. 

Glen said - "Should look like this:" 

I know, I have the LPL C7700 that takes an identical bulb. 

Edited February 23, 2023 by rodeo_joe1

[glen_h]

How about this one?

 

https://www.amazon.com/dp/B016PD5NAW

that is a 7W replacement for a 50W halogen lamp.

 

That suggests that you might need 14W for a 100W lamp.

With a big metal heat sink, where the existing fan can blow

on it, it might work.   (If it has a fan.)

 

It seems to have the GU5.3 base, which might be compatible with GY5.3,

the base of the 82V bulb. 

 

EFP has the GZ6.35 base, which seems to be less common.

[rodeo_joe1]

Hmmm. A quick Google search showed that cheap 12v 'transformers' stop at about 60 Watts, and above that the price shoots up. 

This is the cheapest one I could find that'll drive a 100 watt bulb safely. There was another rated at 105w, but it hardly saves enough money for being so marginally rated. 

I don't see why a LED bi-pin of about 15 watt rating wouldn't work, but those LED bulbs don't have a parabolic focussing reflector. They use a lens array in front of the LED chips - which may or may not put as much light into the condenser/diffuser-box as a halogen bulb. 

Then again, modern photo paper is a bit faster than it used to be. So a 50 watt equivalent LED might be more than adequate these days. 

FWIW, this is as far as I've got trying to shoehorn a high power LED module into my L1000 - 

The heatsink is an old computer CPU cooler from the early Pentium era. There's a little 12v fan screwed underneath the bit you can see. 

I think I might have to fabricate a 'power bulge' to the lamphouse to make it fit!😱

Edited February 23, 2023 by rodeo_joe1

[glen_h]

I am not so sure what the light distribution is out of the reflector.

The filament isn't near a point source, so the focus isn't all that good.

I also don't know at all how the light goes after that. 

It is supposed to be diffused, so maybe more diffusion is good.

[davidbrown57]

I think the direct replacement in the UK is an MR16 bulb - the largest I can find is about 8w that is equivalent to 50W halogen. I think that would just lengthen exposures too much

 

[davidbrown57]

Found this https://www.amazon.co.uk/Spotlight-Projection-Pathway-Garden-Lighting/dp/B07VRNWX3Y

And at £4.29 might be worth a punt. And because its from Amazon could always send it back ....

[glen_h]

3 hours ago, davidbrown57 said:

Found this https://www.amazon.co.uk/Spotlight-Projection-Pathway-Garden-Lighting/dp/B07VRNWX3Y

And at £4.29 might be worth a punt. And because its from Amazon could always send it back ....

It looks like the GU5.3 socket, more like the 82V bulb.

Also, it looks longer than the other, so might not fit.

 

With a condenser enlarger, I have found very short exposure times.  I don't know how this compares.

[rodeo_joe1]

9 hours ago, glen_h said:

Also, it looks longer than the other, so might not fit.

IIRC - it's a long time since I changed the lamp in the C7700 - the bi-pin connector is loose on two wires, and only the front part of the reflector is clipped into the lamphouse. So there's a little bit of tolerance over the length of the bulb. The diameter of the reflector is important though, and I think the diameter of the proper enlarger bulb is smaller than that of a domestic kitchen/bathroom overhead lamp. 

I might well be mis-remembering that, but the boxes that my spare bulbs came in were quite tiny. About a 40mm cube I think. 

Anyhow. That Amazon lamp has two chances of fitting - it'll fit or it won't! 

[glen_h]

11 hours ago, rodeo_joe1 said:

IIRC - it's a long time since I changed the lamp in the C7700 - the bi-pin connector is loose on two wires, and only the front part of the reflector is clipped into the lamphouse. So there's a little bit of tolerance over the length of the bulb. The diameter of the reflector is important though, and I think the diameter of the proper enlarger bulb is smaller than that of a domestic kitchen/bathroom overhead lamp. 

I might well be mis-remembering that, but the boxes that my spare bulbs came in were quite tiny. About a 40mm cube I think. 

Anyhow. That Amazon lamp has two chances of fitting - it'll fit or it won't! 

For the Kodak projectors with halogen lamps, the connector is not on a loose cord.

It does look like the base is different, too, but a loose cord with the other base is not

so hard to find.

 

For only about USD 7.00 each, and 40 hours rated life, you could get a few bulbs.

It seems that they are used in some medical equipment, so are still made.

I was noticing not so long ago, that lamps for Super-8 projectors are hard to

find, and expensive when you find them. Not made anymore.