When LEDs’ wide availability and my interest in pinball coincided in the mid ‘90s, I soon found that apart from the obvious benefits LEDs had, they also came bundled with a number of serious drawbacks - drawbacks which were sufficiently bad they rendered them unusable for my pinball plans.

The intention was to be able to replace all the incandescent lamps in a game with LED equivalents.  Now, bear in mind that was back in the mid-‘90s and LED technology has improved in leaps and bounds since then (even if pinball technology hasn’t).  So perhaps now is the time to re-evaluate what I want a pinball LED to achieve and how close development of the device has brought it to being the drop-in lamp replacement I was looking for?

I was originally only considering how LEDs could take over from #555 and #44 type lamps, but as LEDs have improved, it’s now worth investigating whether flash lamps such as the #89 and #906 can be consigned to the spares box of history as well.

Here is my criteria checklist for LEDs when used as a lamp replacement in a pinball.  I’ll look at each in turn to see how LEDs have changed, and if they now come up to scratch.

To replace a lamp, LEDs should:

If LEDs can tick all these boxes then it’s game over for lamps.  If not, I have to decide if any of the areas where LEDs fall short are showstoppers, or if they can be tolerated for the other benefits they bring.

So, first of all we have:

Consume Less Power
Using less power means power supplies are less stressed and the amount of heat given off by components on the power supply board is reduced.  This helps stop backglasses flaking, boards and connectors burning, and also reduces the electricity bill.

LEDs are intrinsically more efficient at producing light from electricity, so this is a definite win for LEDs.

Generate Less Heat
By producing less heat, the playfield is kept cooler, plastics over the top are less likely to show burn marks or start to melt, and playfield inserts should be less likely to sink or build up dirt on the underside.

LED’s improved efficiency also means they produce much less heat than a lamp.  They are not entirely cool, but any heat generated is tiny in comparison.

Have A Longer Life
The life of either a lamp or a LED depends on two main factors – how quickly does the device burn up its light emitting section and how well does it handle physical shocks.  Lamps fail because they either burn up their element or the element becomes damaged when knocked.  Special versions – such as those used for automotive applications - provide more support the element and give a much improved life expectancy.

LEDs have a much longer lifespan when they are manufactured properly.  Their resistance to physical knocks depends how well the external connections and components are designed and built, but by their nature, LEDs win out again.

Produce The Same Colour
The colour of a white lamp or LED may seem an oxymoron, but lamps do not produce a pure white light.  Their light when correctly powered is actually a bright yellow.  The higher their voltage, the closer the colour comes to being white but when driven too hard, the element will burn out.  Plus, the warm yellow colour is something most people enjoy about a pinball.

LEDs have always had a hard time producing white light.  Early attempts produced a blue-ish hue before the next generation of devices managed a pure white output.  It’s only in recent years that manufacturers have been able to develop that warmer white we need for pinball use.  They have got there, though.

Have Same Fade Characteristics
When power is applied to a lamp it takes a certain amount of time for the element to heat up and start glowing.  Similarly, when power is removed, the hot element continues to glow until it cools.  This 'soft' switch on/off can be a nuisance in some applications, but it’s what we’ve come to expect in pinball lamps.

LEDs behave in a very different way, having very low light persistance.  Once power is applied, they start generating light almost immediately.  They also switch off just as quickly when the power goes away.  When they switch on and off frequently, this gives a very hard, digital look which contrasts with everything we’ve been trying to achieve with the warm colour. 

Newer LEDs generate UV light which hits a fluorescing coating to produce the light.  If this coating could exhibit some persistence like the phosphors in CRT monitors, it might be possible to introduce some fade time, but for now LEDs don’t pass this test.

Produce No Flicker
Pinball machines are designed to use lamps.  The method by which a lamp matrix works depends on the way a lamp continues to produce light for some time after the power is discontinued.  If LEDs don’t emulate this behaviour, you start to see the rapid pulses of power the lamp matrix generates which the lamps themselves disguise. 

This flickering effect can also be produced by the fact general illumination is fed with AC power in many manufacturers’ designs.  Although the 50Hz or 60Hz power is usually fast enough to not be objectionable in itself, the fact that LEDs are polarised and only produce light for less than 40% of each cycle exacerbates the situation. 

Work is under way to change the AC general illumination power to DC on some replacement power supply boards but that doesn’t fix the lamp matrix issue and so LEDs currently fail this test.

Illuminate When They Are Supposed To
This might seem an obvious requirement, but LEDs and lamps operate in very different ways as we have seen, so are there any instances where a lamp will work but an LED will not?

Generally speaking, pinball lamps need a higher voltage and more current than their LED replacements, so both have to be reduced with a resistor which is usually built into the base of a pinball LED.  I haven’t seen any instances where the polarity of the current deliberately changes during operation, so that shouldn’t cause any polarisation problems once the LED is inserted the correct way initially. 

The only issue noted so far is where LEDs draw so little current, they are mis-diagnosed by those pinball operating systems which use current sensing to alert the operator to any dead lamps.  That’s not a major issue and it can be worked around by connecting another resistor across the lamp socket’s terminals to increase the current flow.  So LEDs meet this requirement.

Not Illuminate When They Aren’t Supposed To
If the previous requirement seemed obvious, this one might also appear to be a no-brainer, but in fact it’s become one of the biggest problems with LEDs.

The inside of a pinball machine is, electrically, a very noisy environment.  Solenoids firing rapidly, flashers being pulsed repeatedly and the constant scanning of the lamp matrix all generate spikes and induce voltages in places where they’re not meant to be.  The lamp matrix itself relies on blocking diodes to prevent power reaching adjacent rows or columns and these diodes may not be 100% effective all the time.  So small amounts of voltage and current leak into nearby circuits, and we know that LEDs only require relatively small amounts of each to work.  This results in some LEDs coming on when they are not supposed to.

Is that the fault of the LED?  Some designs are better than others in this regard, but - although it’s not actually the fault of the LED which is just doing what it’s told - it is still a problem in many LED products out there, so it doesn’t pass this test.

Have The Same Brightness (or more, but controllable)
The lighting in a pinball machine is designed in such a way that lamps are placed where they are needed to create a reasonably consistent level of illumination across the playfield and in the backbox, with spot effects positioned where they are most effective.

The light produced by a #555 or #47 lamp was usually the reference used when designing the lighting layout, so any LED replacement needs to be able to produce at least as much light.  Similarly, if it produces too much light, the whole look of the game changes and hot spots might appear in unexpected places.

It’s taken many years, but now I believe LEDs are quite capable of producing the same amount of light as the typical incandescent lamp used in pinball.  Not only for GI and controlled lamp use, but also – by combining multiple devices – as a higher-power lamp and a flasher lamp replacements too.

Produce The Same Light Dispersion Pattern
A filament lamp used in pinball will radiate light in all directions.  The base may block some or all of that (depending whether it’s a bayonet-style or a wedge-style mounting) but otherwise it’s a reasonably even spread of light.

Replicating that spread with LEDs has been one of the biggest problems pinball buyers have encountered.  Most LEDs shine the majority of their light up through the top of the device where a frosted casing may disperse it somewhat, but when viewed from the side, only a small amount of light can be seen. 

As we said earlier, fluorescent coatings on LEDs have improved matters and allowed some light to be emitted horizontally, but the intensity still falls off rapidly once you stop viewing it head-on.  For inserts and spot lamps that’s no problem and can be quite desirable, but for general use, LEDs are not quite there yet.

Have A Range Of Colours Available
The traditional way to colour the light from a lamp has been to put a coloured filter in front.  That filter may be a plastic insert, a rubberised “condom” which fits tightly over the bulb, paint applied the glass bulb or some printed artwork.  These methods take the yellow-white light and strip out all wavelengths outside the filter colour, resulting in a less bright lamp.

LEDs are now available in almost any colour you choose, including dual- or multi-colour versions, and achieve this by producing the desired colour of light in the first place, resulting in a brighter, purer light.  So this is another area in which – if you’ll excuse the pun – LEDs really shine.

Have Flashing Versions Available
Self-flashing lamps weren’t used very often in pinball machines, but they do crop up now and then, so to provide a universal panacea we have to provide for those situations too. 

Fortunately, a flashing circuit built into the body of an LED has been available for many years now, so this should prove to be no problem.

Have The Same Physical Size And Mountings
There are relatively few designs for lamp holders used in pinball machines and the trusty miniature bayonet (BA9s) base has been the mainstay for decades.  While wedge base lamps have become more popular recently, both styles are readily available from LED vendors along with larger wedge and bayonet styles for flash lamp replacements. 

There may be some obscure lamp holders out there, but if the demand is there, people will produce suitable LED bases, or the socket can be replaced with something more conventional.

Cost The Same (or less)
The last criterion is the easiest to test.  A box of 10 #555 or #47 lamps is about $2 at a pinball show. 

To get 10 LEDs costs about $5, so even though the price has fallen quite rapidly in the last couple of years, LEDs are still about 150% more than their filament lamp equivalents.

So, where does that leave me in my quest for the perfect replacement LED?

Consume less power
Generate less heat
Have a longer life
Produce the same colour light
Illuminate when they are supposed to
Have the same brightness (or more, but controllable)
Have a range of colours available
Have flashing versions available
Have the same physical size and mountings

9 out of the 14 criteria have been met, but 5 important ones are not there yet.

Have the same fade characteristics
Produce no flicker
Not illuminate when they aren’t supposed to
Produce the same light dispersion pattern
Cost the same (or less)

Over the coming years, some or all of these 5 may be addressed and the technical difficulties overcome, but for now, this is where we stand.

Now to the big question; are these failings bad enough to make LEDs unsuitable for general use as an all-round replacement for incandescent lamps? 

For me, I’d say they are and I’ll be sticking with lamps for the time being, other than for specific spot effects, multi-colour lighting, very hard to reach lamps and possibly for flashers where the criteria are weighted differently and the extended life and increased light output are tangible benefits worth paying extra for. 

You may come up with a different conclusion, of course.

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