Vintage Synth Explorer Forums

I'm thinking of swapping out the ubiquitous RED LEDS on some of my older synths, and wanted BLUE mainly. I was told blue draws more current. Will this cause problems with the power supply in synths with internal transformers? (or does it only appply to 'wall wart' synths like the AN1x?) - I was told I'd need to up the PSU on the AN1x if I 'went blue'. How would you do this on a synth that has a non swappable internal power supply (as the rest of my synths do).. is it even a problem.

If it was just say 2 LEDs then would the differences be minimal enough to not worry? Obv I'd use new value resistors where needed to keep the supplied juice within tolerance to the new LED.

Also what about those multicolour RGB Leds (that you can alter the mix on) It would be cool to have a pot to adjust the overall colour for all LEDS.

Also I may want to ADD leds (for example on transparent retro fitted Benders/mod wheels) to have it shine through. I'm shooting in the dark here with all things 'power related' (not an area I ever spent much time looking into) so would appreciate a few pointers. I can of course build custom electronics where needed and I've done plenty of mods to synths ok.

Is it possible to find blue LEDS that draw the same or less current as the old 80s red ones, even if you have to buy 'low power/less bright' ones?

thanks for reading my newb-like questions all you eletronics gurus

I'm still kinda new at all this myself though and never done it before. First thing that jumps to mind is to whip out the schematics and see if they have lead-in resistors for each LED. Those resistors could be replaced to have lower ohms so they could pass the same current after switching LED colors. The current change from red to blue would be a ratio that could be multiplied with the original resistor values to give you the new resistor values.

If on the other hand this new resistor values turn out to be just a few ohms then I wouldn't mess with it....after replacing the LEDs just recalibrate any trimpots that may be affected by the minor current differences. You wouldn't want them too dim though, they should be nice and brite. I'm still kinda new at all this myself though and never done it before. Anyone else's thoughts?

Public Safety Announcement. Just so everyone knows. LEDs are after all, diodes. Connecting them backwards turns them into little bombs so use caution.

Blue is way over-rated and harsh on the eyes. Look for a "diffuse" blue, dont bother with the clear blue, its a head ache in very little time. And yes, they draw considerably more current so plan on swapping out the current limiting resistors otherwise you will have quite a flash light..

Thanks guys.

Well what I'd really like is the RGB LEDS (in a pack) not sure how small they can go/if they would fit (some would be on the fascia not just hidden away lighting things). And ideally I'd be able to use a pot to alter the color to suit.. orange, purple, whatever... this of course is merely a curious enquiry. I'm not saying I must have blue/purple/pink/rainbow colours or my synths will be rendered useless - I can live happily with plain old red if it's too much hassle but I like to try things out.

Pro5 wrote:I'm thinking of swapping out the ubiquitous RED LEDS on some of my older synths, and wanted BLUE mainly. I was told blue draws more current. Will this cause problems with the power supply in synths with internal transformers? (or does it only appply to 'wall wart' synths like the AN1x?) - I was told I'd need to up the PSU on the AN1x if I 'went blue'. How would you do this on a synth that has a non swappable internal power supply (as the rest of my synths do).. is it even a problem.

Your advisor is wrong - in fact in most cases the exact opposite is true. Most blue leds are -far- more efficient than red LEDs of yesteryear. Where he may have become confused is that sometimes, especially in multiplexed LED applications, where the required voltage across a blue LED is considerably more than an old red one (ie. typically 3.2 vs 1.5 volts), there may not be enough voltage developed across the junction for a decent light output when using the original limiting resistors. In this case, even if the limiting resistors are reduced in value to regain required brightness, the average power requirement will not increase compared to the original. Where this can become a real issue is in later 3.3 volt designs where there might not actually be enough voltage across the blue led to light it brightly. In this case you may not have any choice but to use green, amber or red.

I changed the LEDs in my Emulator II (a 5 volt design) for blue ones and found that they were slightly dimmer compared to the original red ones for this very reason.

Thanks

The LEDS would have been for the POLYSIX (and I saw a mod for clear bend/mod wheels on the Polysix with a BLUE / RED led thing going on but can't remember where I saw it now nor if it had any guide on how to do it)

making clear wheel using rgb is really easy. there are 4 pins. one of them is G other ones correspond to proper voltage. you can give 5 v with some resistor to those 3 pins. i used 3 pos switch so you can get 7 diffrent colours.