I understand your concerns and you can replace all of them. They work fine.
First, it won't make a difference if you swap out between two or the entire set because only two can be engaged at a time on a single IG00157 or the entire synth.
I have tested these bulbs extensively in and out of the preset panel. I've done some testing on the IG00157 chips too. Fortunately, the IG00157 has a short circuit kill switch built into it if you mess up really bad and the bulb leads touch or something.
If it helps you feel better, here's some more info from my research comingled with a few tips. Cold filament inrush current, PUPD (Power up Power Down), and button bounce (when you press a panel button and it makes contact several times within a few milliseconds) are the most stressful tasks that the IG00157 has to deal with. Cold filament inrush current for an incandescent lamp is roughly 10 times the current consumption that a lamp consumes during its stable operational state. My bulbs consume a third less current compared to the originals in their stable operational state. The IG00157 is not going to care where on the decay curve to the stable state the inrush current starts compared to the originals and lower peak current consumption will probably prolong the life of the chip. I suggest replacing the 100uf and 10uf caps under the preset panel to help keep the IG00157's stable if you are serious about prolonging the life of your synth.
When Yamaha designed the IG00157 and buttons, they had to consider voltage, wattage, heat transfer, and replacement availability of the bulbs. Trying to figure out why the original bulbs had a voltage drop of 13.75v instead of 14v had me thinking for a long time. 5v, 6.3v, 10v, 12v, 14v, and 28v are the industry standard voltage options for the lamp model that goes in the synth. 5v, 6.3v, 10v, and 12v won't work because they'll burn up. I'm assuming that the originals are 1,000 hr to 2,500 hr 14v bulbs because they burn out a lot and 28v would last for ever but look strange. The engineers could have either designed the IG00157 to output voltage a bit lower (a common industry practice to prolong life) or maybe they weren't an exact fit - they could have looked better on paper:) My bulbs run at about 14.05,v which is well within industry specs and have the same lumen output which indicate that they are a good fit. If they were running at 13v or 15v, I would be worried that I had the wrong bulb because current and voltage didn't match up. Putting in higher output bulbs can lower the voltage drop down to about 13v but they really really get hot and could melt the plastic. Again, with higher output bulbs, the cold filament inrush current could be a problem.
The bulbs are not polarized. They will still draw the same current if they are upside down, a/c, dc, etc.
Another thing, when you remove the bulbs, grab the entire rubber mount NOT THE BULB with needle nose pliers and pull up. The rubber mount is held in place by two conductive poles that run through it. you can see the top of the two poles peeking out of each side when you look down on the mount from above. Once you get the rubber mount out, push out the bulb from the top and then reverse the process to put a new bulb in.
-Mike
--- In yamahacs80@yahoogroups.com, rj krohn <r_j_d_2.phila@...> wrote:
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> hi mike, thanks so much for doing the bulbs! i just got my order of them yesterday.ive got 2 questions, if you dont mind, before swapping them out:
> 1-i saw the current draw specs, and how much better they look; have you(or anyone) swapped out the ENTIRE stock set for new bulbs yet? just wanna make sure that its "ok" to do the whole set as precautionary measure.
> 2-im assuming their is a polarity to the bulbs? if so, how do i tell it? thanks again, rj
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