timer question, can I use a 240v timer with 120v enlarger?

Discussion in 'Darkroom Equipment' started by slight, Mar 18, 2013.

  1. slight

    slight Member

    Messages:
    44
    Joined:
    Mar 7, 2011
    Location:
    Paris
    Shooter:
    Multi Format
    Hello everyone.

    This seems a bit stupid but I'm very confused about how to choose enlarger timer, as I have only used Ilford 500 system before and it can be switched between 110v-240v, and its timer is connected directly to the transformer.

    But currently I'm building my LPL 7452 system. I plan to use an Analyser Pro with it. The question is, my lpl 7452 is 120v, while here the wall plug is 240v; should I use a 120v analyser pro (which is a timer/densitometer) with it, or a 220v version?

    I'm very confused here, please help!

    Jing
     
    Last edited by a moderator: Mar 18, 2013
  2. Jesper

    Jesper Subscriber

    Messages:
    728
    Joined:
    Mar 29, 2009
    Location:
    Sweden
    Shooter:
    Multi Format
    You cannot plug a 120V appliance into 240V. It will burn very quickly.
    Could you change the lamp to a 240V version?
     
  3. slight

    slight Member

    Messages:
    44
    Joined:
    Mar 7, 2011
    Location:
    Paris
    Shooter:
    Multi Format

    Yes I am aware that I must use a transformer to use the LPL 7452 when the wall plug is 220v.

    BUT, my questions is, can I plug a 240v analyser pro timer in this 120v lpl 7452 enlarger??
     
  4. RH Designs

    RH Designs Advertiser Advertiser

    Messages:
    657
    Joined:
    Apr 9, 2003
    Location:
    Yorkshire Da
    Shooter:
    Multi Format
    You will need a transformer to convert the 240v mains to 120v for your enlarger. It would be best to use a 120v Analyser Pro, so you'd plug the transformer into the 240v mains, plug the Analyser into the 120v from the transformer, and plug your enlarger into the Analyser's Enlarger socket. Alternatively (and this would be a better solution) you could find a 240v version of the LPL power supply. The Analyser is simply a mains switch so no, you cannot plug your 120v enlarger into a 240v Analyser.

    Is your enlarger a colour or VC head? They use (I think) a 24v lamp so you'll already have a transformer to convert the 120v to 24v - the best solution is to replace that with a 240v-24v transformer.
     
  5. slight

    slight Member

    Messages:
    44
    Joined:
    Mar 7, 2011
    Location:
    Paris
    Shooter:
    Multi Format
    Thanks Richard, that is very helpful!

    But can I actually replace the transformer without burning anything? Because, the lamp itself is a 84v 250w lamp, not 24v. When I replace the 120v power unit into a 220v one, do I need to replace the 84v lamp into a 24v one?

    Thank you!

    Jing
     
  6. slight

    slight Member

    Messages:
    44
    Joined:
    Mar 7, 2011
    Location:
    Paris
    Shooter:
    Multi Format
    I found the following explanations on khphto's ebay store.

    "250W/24V Quartz-Halogen replacement lamp for LPL model 7452 and 7452L 4x5 Dichroic Colour, VCCE Variable Contrast, and B&W Diffusion enlargers with 24V power supplies. The 24V power supplies are typically supplied with these enlargers in areas with 220V or 240V electrical service. "

    Does it mean I can switch the 82v lamp and 110v power unit into a 24v lamp and 220v power unit combo, without modifying anything?? What about the fan? The fan won't burn when the mains power jumped from 110v to 220v??

    Thanks
     
  7. mr rusty

    mr rusty Subscriber

    Messages:
    743
    Joined:
    Sep 7, 2009
    Location:
    lancashire,
    Shooter:
    Medium Format
    Hi Jing

    Yes, I had a quick look on the web and it seems it is an 84V (or 82V) lamp on the 120V transformer.

    It MAY be as simple as just changing the bulb for a 24V one, but it is going to depend what the rest of the wiring is. 250W into 24V is >10A which is a lot more than 250W into 84V which is only 3A. 10A over wiring designed for 3A could get a little warm! It isn't a complex system - just a regulated transformer and a bulb, so provided that all parts match it should be easy to re-build to the new voltage. However, if you are unsure I would take the problem to an electrical engineer - perhaps an auto-electrician, or perhaps electrical engineering at the local college - anybody who knows how to safely build electrical systems.

    However I would probably consider plan A and get a 240v-120v converter transformer - easily available- big/robust ones used on building sites. As Richard says, get a 120V analyser and plug your 120V enlarger straight into it. May well be the neatest/easiest solution rather than messing around with the potential issues of converting a 120V enlarger (if you are not quite sure what you are doing).

    EDIT just seen your remark re the fan - this could also be designed for particular voltage. Suggest external 240v - 120V transformer with a 120V analyser is definitely the simplest route
     
  8. slight

    slight Member

    Messages:
    44
    Joined:
    Mar 7, 2011
    Location:
    Paris
    Shooter:
    Multi Format
    I got it, if I want to modify my 7452 into 220v version, I need to replace the WHOLE lamp house (which includes the fan), the lamp, AND the power unit.

    This is really a pain. I will simply buy a 120v analyser pro, and a 220v - 120v transformer.

    But this leads to another question, will the 220v-110v transformer affect the enlarger's light output stability???
     
  9. slight

    slight Member

    Messages:
    44
    Joined:
    Mar 7, 2011
    Location:
    Paris
    Shooter:
    Multi Format
    Thanks Mr. Rusty, just saw your post. Yes indeed I will now try to finder a decent transformer.

    One thing that concerns me is whether this will affect the current quality and in the end affect the enlarger's light output stability. Is it worthwhile to get a stabiliser along with the transformer?
     
  10. mr rusty

    mr rusty Subscriber

    Messages:
    743
    Joined:
    Sep 7, 2009
    Location:
    lancashire,
    Shooter:
    Medium Format
    No. The Enlarger still has it's stabilizer. The step-down transformer just works to convert your power supply as if it was a 120V supply. Depending on which transformer you get you may need to wire up a lead to convert the socket on the transformer to the socket on the analyser. The chain of devices is:-

    240v mains => stepdown transformer => 120V mains => 120v analyser => 120v enlarger transformer (with its regulator) => enlarger/fan/bulb

    Just one other thought. If you are going to use the analyser safelight output you will need a 120v bulb in the safelight as well.

    If it were me I'd get a building site stepdown. Very easy to find, high rating so won't overheat. Even the smallest are probably 1kW. like this:-
    http://www.ebay.co.uk/itm/110v-Tran...al_Components_Supplies_ET&hash=item43b88819f3

    or you could get something like this:-

    http://www.amazon.co.uk/Goldsource-...ODNI/ref=sr_1_7?ie=UTF8&qid=1363617703&sr=8-7

    I'd go for 1kW minimum, even though you are only drawing 250-300W.
     
    Last edited by a moderator: Mar 18, 2013
  11. Ed Bray

    Ed Bray Member

    Messages:
    348
    Joined:
    Nov 23, 2011
    Location:
    Plymouth, UK
    Shooter:
    Multi Format
    Just something to also be aware of is the frequency of the AC voltage in France is 50Hz whilst the frequency of the AC Voltage in the US is 60Hz, depending on the circuitry this may give rise to some timing errors.
     
  12. mr rusty

    mr rusty Subscriber

    Messages:
    743
    Joined:
    Sep 7, 2009
    Location:
    lancashire,
    Shooter:
    Medium Format
    No, it isn't using the frequency for timing! not a problem.
     
  13. Steve Smith

    Steve Smith Subscriber

    Messages:
    9,042
    Joined:
    May 3, 2006
    Location:
    Ryde, Isle o
    Shooter:
    Medium Format
    That's because it is in series with a diode so it is a half wave rectification of the 120 volt supply.


    Steve.
     
  14. RH Designs

    RH Designs Advertiser Advertiser

    Messages:
    657
    Joined:
    Apr 9, 2003
    Location:
    Yorkshire Da
    Shooter:
    Multi Format
    OK, so it's a b+W head, not a dichroic so it doesn't use the 24v lamp. The idea of using a diode to drop 120v to 84v seems like a bit of a kluge to me but I know it was common practice in the US. The ideal solution would be to find a 220v lamp which would fit the enlarger's socket, chop out the diode and run the whole lot at 220v, but my knowledge of enlarger lamp types is too limited to be able to say if that's a viable option.

    I don't think you would need as big a 220-110v transformer as 1KW, the Analyser's consumption is negligible so you're really only running the 250W enlarger lamp so 500W should be more than enough.

    There is no problem with the frequency difference, our timers have their own internal clock and do not rely on the mains frequency.

    Edit: looking on the web I found this which suggests there is a stabilised power supply for the 82v lamp - if you have that, ignore what I said about the diode :smile:.
     
  15. slight

    slight Member

    Messages:
    44
    Joined:
    Mar 7, 2011
    Location:
    Paris
    Shooter:
    Multi Format
    Thank you very much Richards, that's very helpful!
     
  16. Mike Wilde

    Mike Wilde Member

    Messages:
    2,936
    Joined:
    Aug 10, 2006
    Location:
    Misissauaga
    Shooter:
    Multi Format
    In low volume technical and scientific gear, which usually include photo gear, multi- tap transformers are rather common. They can usally be reconfigured to work with powere sources as found all over the world.

    Finding documentation to figure out what the different taps on the transformer do can be a challenge.

    I have more than a few times in the past bought 220/240 gear from overseas, even without the manuals for voltage conversion and converted them for my north american usage needs.

    I know this is not for everyone, but here is the basic approcach.

    I use an autotransformer (hooked to a GFI/RCD power source) to drive the device with the voltage it originally wanted, and measure the outputs going to the circuit board/rectifier section. Then I unhook the secondary termianls, and measure the voltage again.

    Look at the leads insulation colours, and try to guess which ones might be center taps.
    Look for leads on the primary tied together if coming from a 220/240 market.
    They are likely used to put two 100-140V primary windings into series.

    Unhook the links on the primary. Make ohm meter reading to figure which leads are part of the same winding, and whch ones are different.
    Then figure which ones are at separate ends of a winding, and which ones are likely neighbouring taps separated by only a few turns.

    (keep good notes/lots of digicam snaps, as you go.)

    Usually the 240/220 conversion is to take a primary OEM connections, wired in series, and modify it to connect it in parallel.

    Make educated guess trial connections on the primary, insulate unused leads, put the meter in AC volts mode, and hook it to the secondary leads that you have previously measure the output voltage of.
    Slowly wind up the voltage you drive the primary with from the autotransformer, and stop when you get the desired votage on the secondary. Then go and see what voltage you are feeding the primary. If it is your target voltage you are done. If it is some wierd voltage, then other tap connections that look promising from your ohn meter testing results should be trialled.

    Finally, once all is re-assembled, adjust the overcurrent fuse; it is likely going to need ot be doubled for a 220 to 120 conversion.
    Make note of any shaded pole motors for fans , etc. They may connect upstream of the transformer, and need special treatment. A small voltage step up transformer or surplus autotransfoeras I had, for one project can be added to drive them at 220V etc. if you are on 120V mains. .
     
  17. Steve Smith

    Steve Smith Subscriber

    Messages:
    9,042
    Joined:
    May 3, 2006
    Location:
    Ryde, Isle o
    Shooter:
    Medium Format
    It seems very strange to me too. Just make a 120 volt bulb!


    Steve.
     
  18. RH Designs

    RH Designs Advertiser Advertiser

    Messages:
    657
    Joined:
    Apr 9, 2003
    Location:
    Yorkshire Da
    Shooter:
    Multi Format
    Funnily enough I recently had occasion to find that out - I wanted a quick cheap and cheerful 110v power source and thought the transformer for my LPL 7700 might have a tapped transformer. It doesn't, it's a simple 220v in/12v out. I then looked at a Meopta 12v transformer labeled "220v" and found that it had two primary windings wired in series. So that would be a simple conversion to 110v if required - and it also provided me with the 110v I needed by using the primary winding as an auto-transformer.