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  1. #1
    foto-r3's Avatar
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    OMEGA D5 voltage problems 220V

    This has to do with an OMEGA D5 Dichroic enlarger we recently bought here in Spain. To the best of my knowledge, these enlargers all came with the US voltage and were rigged-converted to 220V. Mine has two big transformers. The problem is: the enlarger works correctly but makes a annoying humming noise from the head --different from the otherwise quiet humming noise of the fan itself. When we hooked it up to a third-party solid-state voltage stabiliser, the fuse pops on the stabiliser every so often. I suspect that these enlargers do not normally make this annoying humming noise. Can anyone verify this, and, has anyone had a similar experience with voltage conversions and-or voltage problems that could shed some light on this...thanks.

  2. #2
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    Quote Originally Posted by foto-r3
    This has to do with an OMEGA D5 Dichroic enlarger we recently bought here in Spain. To the best of my knowledge, these enlargers all came with the US voltage and were rigged-converted to 220V. Mine has two big transformers. The problem is: the enlarger works correctly but makes a annoying humming noise from the head --different from the otherwise quiet humming noise of the fan itself. When we hooked it up to a third-party solid-state voltage stabiliser, the fuse pops on the stabiliser every so often. I suspect that these enlargers do not normally make this annoying humming noise. Can anyone verify this, and, has anyone had a similar experience with voltage conversions and-or voltage problems that could shed some light on this...thanks.
    I'm going to assume that the humming is still there even when you use the voltage stabiliser, if so then read-on. Also I'm going to assume that voltage stabiliser outputting 220VAC (rather than 110VAC).

    The most likely cause of the hum would be the step-down transformer (220V-110V). If an under rated (power-wise) or poorly designed step down transformer is used you will over-load it causing hum. If there is a rating on this txformer then see how it's power rating compares to the power needs of the enlarger.

    A humming transformer is operating inefficiently and will draw more power than it should. So if the fuse on the voltage stabiliser is chosen exactly for the enlarger (i.e. the ratings were chosen to match) then the additional (unnaccounted) power drain in the humming transformer core will blow the fuse (albeit intermittently if it is just over the limit since fuses are not binary in nature, they obey a time*current curve.)

    So if that is the case, I'd get the step-down transformer replaced with one that can handle the power drain of the enlarger. If the step-down transformer is sufficiently rated then get another one anyway because it is probably a bad design ! Toroidal transformers are quieter conventional shaped (cubical ?) txformers and are used in audio amplifiers for this reason.


    regards
    Peter




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    I'm not sure what in the head would be humming if you've excluded the fan - it depends what other components are inside as to what it is and what is the cause. Is the hum coming from the power supply or the components within the head? My Durst power supply does hum quite significantly when it's providing power to the lamp but it's normal. If some components in the head are expecting a DC voltage and are receiving some AC then you might have a faulty rectifier or capacitors in the power supply. Does your voltage stabiliser completely replace the supplied transformer? If you're blowing the proper type and rating of fuses in the stabiliser, then as Peter suggests it probably doesn't have the power rating to drive the enlarger. Sorry I can't be more help.

    Roger.

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    Without physically examining what someone else has done by way of a conversion I am guessing as to a source of a bothersome hum.

    It may be that your conversion has a contactor installed in the head itself to do the switching of the voltage to the lamp. This would typically be done to shed the load of the lamp off the enlarging timer. Contactors, which are electrically operated switches, can hum because the electromagnetic coil represents an inductive load whereas a typical incandescent lamp will be a resistive load.

    If there is nothing in the way of auto focusing on the enlarger, there would typically not be a requirement for a stepping transformer. All that would be required would be to install a lamp of the proper voltage and wattage.

    A regulated power supply would typically be of limited benefit in black and white printing. It would be more applicable to situations where a lamp emission color shift could occur with voltage fluctuations.

    In regard to your interrupting current by blowing fuses, I would suggest that you confirm the proper sizing of the device. The way to determine this is to divide the wattage by the voltage and the result would be the amperage that would represent the load. A slight oversize of fuses may be appropriate if the device is not undersized.

    Transformers are typically sized by VA (volt/amp) designations. This would be determined by determining the amperage as I described above and multiplying this by the output voltage of the transformer.

    An example of determining these calculations would be as follows: The enlarger has a 1000 watt lamp and the supply voltage is 230 volt 50 hz.(Europe) the amperage requirement of the device would be 4.34 amps. The proper sizing for a transformer to supply this load would be a minimum of 998.20 or more typically expressed as a 1KVA transformer. However in actual practice one would be more accurate in sizing this as 1.5 KVA and the fuse to protect the device should be sized at 6 amp and installed on the secondary (output) winding circuit of the transformer. This would allow proper operation of the equipment and provide the necessary safety factor to protect the device.

  5. #5

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    Quote Originally Posted by foto-r3
    This has to do with an OMEGA D5 Dichroic enlarger we recently bought here in Spain. To the best of my knowledge, these enlargers all came with the US voltage and were rigged-converted to 220V. Mine has two big transformers. The problem is: the enlarger works correctly but makes a annoying humming noise from the head --different from the otherwise quiet humming noise of the fan itself. When we hooked it up to a third-party solid-state voltage stabiliser, the fuse pops on the stabiliser every so often. I suspect that these enlargers do not normally make this annoying humming noise. Can anyone verify this, and, has anyone had a similar experience with voltage conversions and-or voltage problems that could shed some light on this...thanks.
    Is the fuse blowing when you turn the lamp on, or while the lamp is operating? In either case, the stabilizer may be underrated for your load. If the power rating of the stabilizer is close to the lamp wattage, it may actually be underrated. The transformer will waste some power. The lamp will draw a very large inrush current when you turn it on.

    Re the humming in the head: is there anything in the head besides the fan and lamp? Take a look with the power off. Are you sure that the sound is from the head? I could easily believe the transformers humming, perhaps you are having trouble localizing the sound.

    A better solution would be to switch to a 220 V lamp and fan, or at least to switch the lamp so that you don't have to use a high wattage transformer. If Omega made / makes a 220 V version of the head, you could try finding out what lamp they used.

  6. #6
    foto-r3's Avatar
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    First, thank you all for the feedback.

    The humming sound comes from the fan-side of the lamphouse, and not from the transformers, of that I am sure. The fan purrs, while this humming sound is distinct. The humming happens with or without the voltage stabiliser. Something I did not clarify: the fan cable is not plugged into the voltage stabiliser. We plug the lamp cable into the back of the voltage stabiliser's output socket (which has a power rating of 600 VA). The voltage stabiliser and timer are two separate units but are wired together (the timer does not have its own socket). We did some tests on another enlarger, a Varioscop, which only has one plug (and no fan), and operation appears normal, no fuse popping.


    On this enlarger, there is one cable with socket for the lamp that gets plugged into the timer and another plug for the fan that goes through two transformers. Something I did notice is that, when jiggling (or moving) the fan cable with "homemade" switch, the fan motor proper begins to make a strange, high-pitched noise but then will stop once you "crimp" the cable "back in place" -- this suggests some kind of faulty connection and I hope to get to the bottom of it this weekend.

    Another issue is: we have not yet grounded our electrical installation. We will do so this weekend. Not sure if this has any bearing on it or not.

    Anyway, I will get our electrician friend to put a meter on the cables and hopefully we can get to the bottom of this.


    Thanks again for your help.

  7. #7
    foto-r3's Avatar
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    Lamp power?

    After metering the voltage, we found that the current entering the house is about 184 and not 220V. The reason why our voltage stabiliser is popping is we are using a 250W 24V bulb and this would require a much more powerful unit. We grounded the connection but this made no difference as far as the humming. We also replaced the suspicious cable. No improvement.

    My question is: what is the minimum bulb that can be used with this enlarger? 50 / 100W? The idea is, by lowering the wattage of the bulb, we can make it work with the voltage stabiliser (600W) -- anyone handy with calculations and can tell me the max lamp power for use with this stabiliser.

    Any input is greatly appreciated.

  8. #8
    Monophoto's Avatar
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    Is the head on the enlarger the original head that came with the unit when it was sold in North America?

    If so, the problem may be a combination of two factors. First, as you have noted, the input voltage to the house is 184 rather than the nominal 220. If the step-down transformer was selected based on nominal ratings, that means that the actual input voltage to the enlarger head is 92 volts rather than 110. This means two things. First, the bulb will not emit as much light, and the color temperature will be warmer than specification. I suspect that is something that you can adjust for in using the enlarger.

    Second, with reduced voltage, the torque produced by the fan motor is less than rated. If the rated input voltage is 110 v, the motor will only develop 69% of rated torque when the input voltage to the house is 184.

    The second factor is that if the head is the original equipment furnished for use in North America, it was designed for 60Hz. The utility grid in Spain is 50Hz. This difference won't mean much for the lamp, but all things equal, the fan speed will be 5/6 of the design speed.

    The combination of reduced voltage and frequency (relative to rating) will likely result in both abnormal vibration and heating in the fan motor.

  9. #9
    foto-r3's Avatar
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    Thanks much, Monophoto, for your assessment of the situation. Yes, the head is an original. What we don't know yet is if the power company will remedy the situation, which, as it seems, is fairly widespread where we are, in a "rural" area. Apparently, if they boost the voltage for us, then this may create problems of over-voltage for houses closer to the transformer, or at least this is what they have told other users with similar problems.

    Another suggestion I received was buying an adjustable transformer that could be adjusted to the real voltage entering the transformer (to compensate for the fact that we are getting 184 instead of 220). Personally I have never seen one of these. What remains to be seen is if this voltage remains constant throughout the day. My friend suggested that at night when there is little consumption this might change, but I do recall using the enlarger at night with the same problem.

    So most probably we will have to get a radio for the darkroom to drown out the hum. Times like this make me recall the spartan wisdom of E. Weston and those of like habits.

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    There are a couple of ways to assure a constant voltage supply to your enlarger. The first would be to use a buck and boost transformer. The second would be to use a variac capable of supplying over supply voltage on the outputs to the load. The first is self adjusting and self compensating. The second is user adjustable.

    It is important to recognize the conventional transformers are proportional devices. So as input voltage is varied so is output. Second transformers are amperage sensitive devices. This is due to the size and number of windings in the design. Therefore if your power supply is sized for 600 watts at what voltage is that calculated? If that is sized for 600 watts at 24 volt then you have no need to resize your lamp. In fact by supplying lower then design voltage you are placing less demand on your transformer then if you were supplying the proper voltage. For light output this is not a good thing since your lamp is emitting 200 watts rather then the 250 design wattage. As previously mentioned this will cause a color shift which is only a problem in color printing. It should not cause much problem in black and white printing.

    The second thing to recognize is that there are two types of electrical load. The first is inductive and is characterized by such devices as transformers, coils, and motors. The second type is resistive and it is characterized by such devices as resistance heating elements and incandescent lamps.

    The hum that you are hearing is probably due to the characteristics of your cooling fan motor. Not only are you supplying a different voltage frequency but also a different voltage.

    There is another way, possibly, of solving this problem. You can seek to find a fan motor that will operate on 50/60 hz (either frequency). If this is a fan of the type used in cooloing applications on devices such as computers, there are probably fans available to meet your needs.

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