Philips HPL-N
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Standard High Pressure Mercury Lamp with 50W, 80W, 125W (E27 base) and 125W, 250W, 400W, 700W, 1000W (E40 base) Features
Lamp control gear
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Best retro purpose
Mercury vapour lamps were traditionally used on industrial and street lighting and they can be used on these areas although LED lamps offer much better performance with lower energy consumption. There are still some specific uses that are specific to this technology. Light appearance is cool white with a bias towards reds as well as blues, and, especially ultraviolet.
Although this is rarely specified or even mentioned in datasheets, UV-A emission is significant if the lamp is used as is, with no cover. This means that most surfaces that are painted white look even whiter in this light. Trees foliage is also emphasized, so this type of lamps are very well suited in gardens. Flowers are not as well showcased as some colours are missing except for red, orange, white, blue and violet. The amp themselves do release quite a lot of heat meaning that closed fixtures are not well suited if not specifically built for this purpose.
Houses can be properly light but such a lamp is less suited for living rooms, bedrooms but is well suited for workshops, halls or any other space that requires wide area lighting. Generally, low power lamps such as 50W are to be avoided as they are quite fragile so typical applications focus on 125 and 250 watt lamps and 400, 700, 1000W lamps are typically too large or cumbersome to be used as free standing lamps or in light fixtures. Due to the fact that fixtures are getting harder to find, outside applications such as area lighting should consider a minimal protection for lamps, meaning that floodlighting is harder than in the past. Of course, any metal-hallide and high pressure sodium fixture can be adapted, if found.
Understanding manufacturer data
Lamp light output is always measured in lumens. This is a way of measuring by averaging light output at a distance of 1 meter in an integrating sphere. This was carried out in lab environments and this information was mentioned in lamp datasheets and catalogues. While this information is accurate it should be considered only across similar lamp types.
Lamp life is presented in thousands of hours. It does not point at a specific moment when an installed lamp will not operate anymore but a statistical point at which some of the lamps may not operate, giving a rough estimate of useful life.
Ra8 colour rendering index, or simply colour rendering index is a way of expressing the typical colour rendering capability of a lamp. While it may be non-intuitive this is a computed average of brightness of certain coloured samples that are light by the lamp. The brighter they are, the more efficient is the lamp in this task. Most lamps do not have a continuous colour spectra so only some specific colours might look very bright and others look very dull. Colour samples are not intense reds, greens and blues but intermediately vivid colours that are focused on human skin colours and some fabrics or surfaces, meaning that a only very high colour rendering indexes are desirable for indoor home lighting. Sun light renders colours almost perfectly, having a value of 100 while typical lamps have a rendering index between 50 and 80, a good value being above 80 and a poor one below 50.
Colour temperature is another important detail. The value is presented in Kelvins and follows a theory that boils down to the fact that light can be produced by heating a metal up to a specific temperature. A camp fire releases light as the flame reaches around 1500-2000 degrees Celsius and a slightly higher value expressed in Kelvin. The designation is warm white for a value of around 2700 Kelvin, natural white with a value of around 3200-3500 Kelvin, cool white for a value of around 4000-4500 Kelvin, daylight for a value between 5000 and 5500 Kelvin, and cool daylight for a value above 6000-6500 Kelvin. There are cultural preferences that make some warm colour temperatures preferred in colder climates and cool colour temperatures in warmer climates. The most popular home lighting worldwide is mostly warm white, due to a comfortable, pleasant atmosphere that is close to the old incandescent lamp.
Technical details
| Designation | Base (Edison Screw) | Lamp wattage | Luminous flux | Colour appearance | Colour Temperature | Colour Rendering Index (Ra8) | Operating Position |
|---|---|---|---|---|---|---|---|
| HPL-N 50W/542 E27 SG SLV | E27 | 50W | 1800lm | Cool White | 4200 K | 49 | any |
| HPL-N 80W/542 E27 SG SLV | E27 | 80W | 3700lm | Cool White | 4200 K | 48 | any |
| HPL-N 125W/542 E27 HG SLV | E27 | 125W | 6200lm | Cool White | 4100 K | 46 | any |
| HPL-N 125W/542 E40 HG SLV | E40 | 125W | 6200lm | Cool White | 4100 K | 46 | any |
| HPL-N 250W/542 E40 HG CRP | E40 | 250W | 12700lm | Cool White | 4200 K | 45 | any |
| HPL-N 400W/542 E40 HG CRP | E40 | 400W | 22000lm | Cool White | 3900 K | 45 | any |
| HPL-N 700W/542 E40 HG CRP | E40 | 700W | 38500lm | Cool White | 3900 K | 45 | any |
| HPL-N 1000W/542 E40 HG CRP | E40 | 1000W | 58500lm | Cool White | 3900 K | 36 | any |
Note: there are other bases such as, for instance, the British B22D or the American E26 and E39; HG means hard glass, SG means soft glass;
Durability and Repair-ability
Generally, mercury vapour lamps were very durable but more modern products were released with lower typical lifetimes. This is mainly due to the fact that upto the 70s, even into the early 80s, manufacturers focused on better performing lamps but this was detrimental to sales. Many installations were left as is with extremely old lamps that were still working, despite very low light output with a greenish tint, since they were not turned off and repairing them cost more than leaving them as is. Also, keep in mind that electricity was very cheap at that time. Many lamps could still operate with broken outer bulbs and left to be blown by wind, cope with mist and frost, although they were dangerous due to UV-C output.
Compared with modern LED lamps, mercury vapour lamps fare very poorly, as they have noticeable light output and quality degradation over 10.000 hours. However, they do have advantages. Hot or cold air affects them very little and they can survive direct operation in free-standing position, meaning with the lamp suspended on wires, even for their entire operational life. Ballast can survive tens of years if properly protected against direct rain or snow exposure. A very simple circuit means that lamp servicing is straightforward and risks are similar to mains voltage operation. 125 and 250 watt lamps are very well built and they were highly popular.
Greatest features & flaws
| Features | Flaws |
|---|---|
| High light output in very compact package | Serious risk of glare |
| Highlights white walls and gardens | Not suited for main interior light |
| Mostly omni-directional light | Unavoidable light flicker and some heat output |
| Very simple circuitry and operation | Requires bulky, heavy lamp gear |
Review
These high pressure mercury vapour lamps are compact light sources that are viable for wide area lighting. Their average colour reproduction and large output means that they are better suited to outdoor lighting. Compared with flourescent lamps they were very compact, having better performance at low temperatures. A longer lifetime, that was around 10 to 15 times higher than tungsten lamps, meant that these lamps are well suited for use in places where lamp replacement was costly, as in high bay lighting and street lighting. They had similar useful life as fluorescent lamps. High pressure sodium lamps had higher light output, almost double, of mercury vapour lamps while having low quality colour reproduction. This means that mercury vapour lamps were still suited for areas where colour reproduction was moderately important and there was still an advantage from compact light sources, which means industrial and workshop lighting, sometime even commercial premises.
Fixtures are generally compact, considering the light output made available, but are generally heavy due to the bulky electromagnetic gear being used. There are directional and omni-directional fixtures that are suited to various purposes. In street lighting, the well known cobra-head style lamppost was used, and they may still be available for purchase. They were only moderately effective as light covered a large area but a considerable amount of light was lost due to the fixture directing some of it upwards, with no control. Omni-directional fixtures were used in residential areas and parks, where ambience was more important than efficiency. Indoor fixtures were centered on the typical high-bay or low-bay purposes, having a metal parabolic reflector and directing most or the entire light output downwards. Other fixtures were compact, having a boxy design, with a symmetrical or asymmetrical lamp placement that was suited for flood lighting. These type of lamps were used indoor as well as outdoor, for floodlighting. There were no home designed fixtures as these lamps were not popular in home environments and were mostly used as porch lighting with a fixture design similar to street or area lighting.
Nowadays, mercury vapour lamps are very well suited for outdoor lighting. As the number of available fixtures diminishes and only second-hand or used products are available, they may not be economically effective to purchase except when you can readily use them rather than collect them. Free standing lamps are quite capable on their own so if you need a compact light source that is highly durable and colour output is appreciated as is, then high pressure mercury vapour lamps are well suited. They are especially well suited for lighting in areas that are undergoing renewal work, workshops, gardens. Of special interest is renewals, since no modern LED lamp can output the same light spectra that dulls old painted areas and brightens newly painted ones.
Operation
These lamps are not well suited for frequent switching. They need a couple of minutes to reach maximum light output and they require a couple of minutes to restart after being turned off. The light colour and output changes from start-up to normal operation from a pink to white. A good lamp should have a strong pink light at startup, suggesting good internal coating performance. As the lamp ages, the coating degrades and light turns greenish.
The lamp requires a conventional or electro-magnetic gear of the same power output as the lamp, connected in series with a lamp. Connecting the lamp directly to mains damages it instantly as there is no current limitation. A power factor capacitor that has a specific value might be used to correct the power factor and current requirements on the circuit. The lamp itself is not influence by the presence or absence of this capacitor. When used sparingly in homes or some premises where not a lot of these lamps are located, power factor correction is not important but large industrial or commercial clients were required to maintain a specific power factor due to electricity distribution contracting.
Suitability The best lamps in terms of useful lifetime, colour reproduction, light output, are the equivalent OSRAM HQL branded lamps, not Philips HPL-N lamps even if Philips lamps were very popular. Chinese branded lamps are much worse in all performance and quality metrics with a greener light output and poor reproduction of oranges and reds. Reflector lamps are generally less versatile than the classic one for most purposes but they do not require any fixtures in most instances.
The best choice of wattage are the 125 and 250 watt lamps as lower wattages have quite a low light output and larger powered lamps are bulky and too powerful for most purposes. The above lamp wattages are also cheaper as they were highly popular. Electro-magnetic ballasts or conventional gears are plentiful and can be used interchangeably with all manufactured lamps for a specific wattage. Lower rated power output gears can be used, making the lamp operate dimly but higher powered ones damage the lamp due to overstressing and are dangerous.
Used lamp gears might work but old lamps are not as desirable. Rusted ballast may still operate but are a potential hazard while old, used lamps, may not have much useful life left and they may already exhibit some colour light emission issues. New old-stock lamps are the best choice, if available.
History
HPL-N lamps are high pressure mercury vapour lamps that have been produced, with somewhat similar properties, since the 1950s. The lamp's fluorescent coating technology dates back to around the end of 1930s while modern lamps were essentially manufactured as early as 1970s and are a result of subsequent improvements up until that time. The market for these lamps grew as industry and commercial activity recovered after the Second World War, meaning that research was justified by large sales. The energy crisis meant that clients demanded improvements and they were focused on improving these lamps, giving rise to derivatives such as metal-hallide lamps, with much better colour reproduction and lower energy consumption. Sodium lamps were improved, culminating in the high-pressure sodium lamps that, with their yellow-orange or golden glow, dominated exterior lighting. By late 1980s mercury vapour lamps where on a market share decline that laster
These lamps were not intended for home or office use and they were seldomly used as such. Tungsten lamps had perfect colour reproduction and electric energy costs were very low. Even after the oil crisis of the early 1970s, tungsten lamps were still cheap enough and convenient to be used for general lighting. Also, these lamps did no require any gear. As mercury vapour lamps were heavily used in street lighting and industry. This means that development focused on colour reproduction but energy efficiency and reliability increases were most successful.
In the p
A midrange, quite slim, business laptop, released in 1998. It had an average mix of parts. Perhaps the single biggest issue is that the whole Dell CP and CPi range is very complex and difficult to understand. Differences between CP and CPi models is minimal in terms of aesthetics while most configuration options are difficult to spot. The major performance jumps are shown in the CPi lineup that has a Pentium II CPU model with major performance improvements, although the Pentium I option is still decent. The graphics chipset is quite fast, actually the best among Pentium I laptops, with good Windows acceleration and compatibility. Another rare feature is the presence of USB ports on a Pentium I era laptop, which is very nice and useful.
However, the typical mix of features of these laptop models mean that it also was obsolete by late 1998, just as most of the mid and high end IBM laptops, due to a lack of 3D acceleration. Windows 98 SE is a typical choice, especially if you have at least 32MB of RAM available. The Neomagic graphics is the top performer on 2D graphics both for compatibility as far back as Windows 3.1 and DOS as well as competitive with Chips&Technology or S3 Trio 64 videocards.
The LCD TFT screen is somewhat alright but far from being the best in terms of contrast and colour reproduction. However, the screen's brightness can be quite pleasantly set using keyboard shortcuts, as the laptop has somewhat more levels to choose from. As usual, DSTN or passive matrix screens should be definitely avoided due to their poor contrast, response, colour reproduction and brightness levels, no matter how lightly they were used.
The keyboard is not as pleasant to use as some IBM models, feeling somewhat light on keypresses. The palmrest is comfortable although the trackpad is somewhat bad in terms of sensitivity and response, being quite dependent on ambient humidity, as is also mentioned in the operating manual. The choice of a trackpoint system would have been much better. Also, due to the laptop's design, the lower area near the mid part of the laptop's case, between bays, is a common failure point due to the simple screw mounting point with no additional stiffening brackets.
The removable drive tray is a nice feature, offering both CD-ROM and Floppy drive support, which was a staple of period DELL laptops . The rechargeable battery has an unique self test feature that also shows the charging level by a simple button press. The BIOS and suspend battery uses a set of non-standard NiMh cells that can be quite messy if worn enough.
The lid closing latch is quite badly designed as it compounds the issue with cracks midway on the palmrest and cases's edge. The display's case is quite flimsy although the frame itself is reasonably well engineered. The integrated speakers are somewhat poor despite their positioning and size, being quite prone to failures due to water ingress.
The standard HDDs are quite competent in terms of size and performance, being well accustomed to the rest of the laptop's configuration.
Software support is great for reasonably modern (for its time) operating systems. Due to the video chipset, Windows 98 is the best operating system choice. Good DOS sound support is present due to the CrystalWare audio chipset that is Sound Blaster compatible, offering good MIDI and software support in MS-DOS.
Manufacturing specificities
Philips has been releasing lamps for many decades. Lamps produced in the 70s and early 80s are probably not commonly found today. In the 90s and early 2000 Philips was manufacturing lamps in Holland and other countries, while in the last years they were doing the same thing in China. Quality was not severely affected as, realistically speaking, there were some occasional lamp defects even in their Holland produced lamps due to average manufacturing quality. It should be noted that mercury vapour lamps were mass manufactured and considered low-cost products, meaning that quality was not paramount.
Until the manufacturing plants move to China, there were small differences in this product line as the 90s and early 2000s was using the same technology. Chinese built lamps have some slight improvements that leave some aspects to be desired as well. The internal coating is thinner and has a different grain size with a potentially different powder mix, improving colour rendering more than what the datasheet suggests. Lamp lumen maintenance and uniformity is improved due to a thinner coating that degrades slower and more uniformly. However, the lamp light looks whitish-green rather than whitish-purple, which might be unpleasant for some persons.
Products manufactured by Philips were similar to General Electric but with a quality and consistency much above some East-European manufacturers in terms of colour rendering, light output and life. However, Philips was manufacturing lamps with shorter lifetimes and poorer internal coatings than Osram ones, even if some values specified in datasheets might not suggest much. These differences were maintained until the end of mercury vapour lamp production in the late 2010s. This Philips-Osram lamp difference must be experienced in person. On the other side, Philips lamps were much more popular and are easier to find.