Electronic transformers designed for Halogen lamps will kill LEDs.
Electronic transformers are very simple switched mode power supplies. They "chop" the input 230 V/125 V sine wave in a way that will yield an average output voltage of 12 V. However, the peak voltage will be much higher and will eventually kill LEDs (that's no problem with Halogen lamps because they react more slowly). In addition, the chopped waveform may cause radio interference if the cables to the lamps are too long. The waveform may also be the reason why your voltage readings are off.
Instead of an electronic transformer designed for Halogen lamps, you should either use:
- a conventional AC transformer (the heavy kind); or
- an electronic DC transformer designed for LEDs.
First of all, when you read about a "50W LED", it is certainly saying that it outputs the equivalent light of a 50W incandescent light (although that is often a exaggeration). That "50W" LED actually draws less than 10 watts. This means that it draws much less current and emits much less heat, both of which are the factors that typically limit the allowable light in a fixture.
You'd be able to replace a 50/100/150W 3-way with a lower wattage, even if staying with incandescent.
Second, unless the LED light is marked "dimmable", don't try to use it on a dimmer. You may damage the dimmer, light, or both. Even if the light is dimmable, some dimmers will not work well with a low load: a dimmer that works on a 100W light bulb may not work on an equivalent-light-output 13W LED. They make LED/CFL specific dimmers that may work better.
As for the 130V R40, that is probably a "long life" bulb. Running an incandescent at lower than rated voltage extends its life. Therefore, they make 130V bulbs to run longer on 120V. Just use LEDs rated for 120V.
As for your existing florescent lighting, I assume you're talking about the straight tube type. For a fixture that old, it's probably less efficient that newer florescent fixtures or LEDs but still much more efficient than incandescent. This is harder to replace with LEDs, just due to the area covered. There are LED tubes made to replace florescent tubes but they are still expensive and generally require re-wiring the fixture. These are most often used in commercial applications.
Best Answer
One problem with this approach is that LEDs are not incandescent bulbs.
LEDs (stripped of the on-board driver circuit which normally handles that part) are "current mode" devices - that is, an LED driver closely controls the current through the LED, and the voltage may vary. When driving multiple LEDs, they either need to be in series and driven off a driver with enough voltage capacity to run the whole string at the desired current, or you need multiple current controlling circuits.
You cannot simply say that the average voltage they use is 3, 12, 23, or 42 volts and supply that voltage to them in parallel; you must control the current, and if you don't, you'll almost certainly destroy them. If they happen to be 42 volts, running 10 in series is a bit challenging as you'd need a driver capable of supplying 420 (or 400-450) VDC at the appropriate current , while for 3V or 12V modules it's much easier to find drivers that might run 10 in series.
I'm not aware of LED fixture manufacturers providing the information about the drive requirements of the LED module - certainly none of the 3 fixture types I use has that information in the data sheets, as they are expected to be connected to mains voltage, and the manufacturer does not expect nor support modifying the fixture (including driver) as-built. As such you (or a good electrician who actually understands LEDs) would need to measure a "functioning" fixture to determine what the drive current and general voltage range are in order to choose a driver and wiring scheme sufficient to run 10 fixtures; Unless, of course, the driver modules you are replacing provide that information on themselves.
If you move back to the makers of the actual LED module, (or "light engine" as some call it) there's all sorts of drive data, but it's generally impossible to get a fixture maker to identify the module they use (and it may well change from time to time or batch to batch.)