# Change Led In Boss CE-2 Chorus?



## Guest (Jun 29, 2015)

I just got a minty early run CE-2 but the led is out, and i am using the correct 12v supply from my PP2.

Can I use any led or is there a special one just for Boss?

Thanks.


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## vadsy (Dec 2, 2010)

I think any regular LED will work. I'm not sure how they might be different but I've replaced Boss LEDs with just the usual stuff I get from Mammoth Electronics.


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## vadsy (Dec 2, 2010)

Just a question, does it matter if you're using 12 volts rather than 9?


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## Chitmo (Sep 2, 2013)

The older Boss pedals need the 12v to funcion when using a power supply. I have a CE-2 that was made in 81 and that's what I use without any issues. Great pedal BTW.


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## vadsy (Dec 2, 2010)

Thanks. 
I wasn't sure, it just seemed strange. My early 80's SD1 and just recently a 1980 CE2 both listed in the manual and worked on 9v power supplies.


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## mhammer (Nov 30, 2007)

"Work" is a loaded term.

Certainly everything in the pedal is able to function on 12VDC without risk to the lifespan of the components. *BU*T, you may need to diddle the trimpot inside to get an optimum sound. I emphasize "may", because the bias set by the trimpot, using a 9v supply may or may not be optimum. If you find the tone a little gritty/dirty on 12v, then that would be a giveaway that the bias needs resetting. Doing so will not compromise the delay chip, however there will be a iimited range of useful settings. Too low or too high, and the chip won't pass signal. Just a bit too high or too low and you'll get delay signal, but it won't be clean. It cleans up when the bias is in the sweet spot. If it is already in the sweet spot, then no worries.

As for the LED, contemporary LEDs are often several orders of magnitude more efficient than what Boss used in the early 80s. A typical red LED had a luminance rating of maybe 600 millicandles. These days, the typical blue LED has a rating in the range of 10,000 millicandles and 20,000 is not uncommon (that's how they can be used for car signals). To use a modern LED without blinding yourself, you will need to replace the current-limiting resistor to drop the brightness down. The schematic below shows it as 3.9k for a 9v supply. At 12v, I would probably _start_ with 15k, and work upwards from there. If it's still too bright, go for 22k. This will depend on the efficiency/brightness of whatever you use to replace it with.


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## greco (Jul 15, 2007)

mhammer said:


> As for the LED, contemporary LEDs are often several orders of magnitude more efficient than what Boss used in the early 80s. A typical red LED had a luminance rating of maybe 600 millicandles. These days, the typical blue LED has a rating in the range of 10,000 millicandles and 20,000 is not uncommon (that's how they can be used for car signals). To use a modern LED without blinding yourself, you will need to replace the current-limiting resistor to drop the brightness down. The schematic below shows it as 3.9k for a 9v supply. At 12v, I would probably _start_ with 15k, and work upwards from there. If it's still too bright, go for 22k. This will depend on the efficiency/brightness of whatever you use to replace it with.


Interesting, informative and very helpful. 

This is the first time I have bumped into a millicandle.

Thanks

Cheers

Dave


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## mhammer (Nov 30, 2007)

That's what the "mcd" is, and denotes the brightness that can be expected at the current rating. This one is rated at 5000-10000mcd.

https://www.dipmicro.com/store/LED3B

Since they are that much brighter, one doesn't have to feed them as much current to get the same brightness you'd find in a traditional Boss status LED. One of the other perks of such "superbright" LEDs is that, since you can make them bright with substantially less current, it extends battery life a bit (although some of us are looking at batteries in the rear-view mirror). Indeed, in some pedals, the status LED consumes more current than the actual effect circuit! So, being able to drop LED current consumption by 80% and more, is a nice little bonus.

I actually made myself a little LED tester, using a 12-position switch. It can select resistor values ranging from 1k-18k. I set it to 18k, connect the battery, and stock an LED into the socket. I then turn the switch down, a step at a time, until I reach a brightness range that seems optimal. If 4k7 seems a little bright, but 6k8 is a little dim, then I know to use a 5k6 in series with the LED. And if 18k still isn't dim enough, I know to go bigger. The nice thing about this is that the switch positions are known resistor values, so I don't have to measure anything. It's a helpful little gadget when pulling an LED out of the parts drawer, and I don't have any information about it handy.


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## Guest (Jun 30, 2015)

Mark I thought the Boss ACA adapters are 12v? I know that the setting on the Pedal Power 2 for #1-4 with the dipswitch on is for Boss ACA pedals.

Yes the pedal is easy to distort. It works nicely when giving it a hot really overdriven signal from my Barber Tone Pump OD, but a clean signal gets hairy or fuzzy easily.

Is there actual Boss LED lights that I can get? Adding things to the circuit is more than I am comfortable with...


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## mhammer (Nov 30, 2007)

Player99 said:


> Mark I thought the Boss ACA adapters are 12v? I know that the setting on the Pedal Power 2 for #1-4 with the dipswitch on is for Boss ACA pedals.


Well, you're outside the perimeter of my knowledge, there.



> Yes the pedal is easy to distort. It works nicely when giving it a hot really overdriven signal from my Barber Tone Pump OD, but a clean signal gets hairy or fuzzy easily.


That's where including a compander chip in the design comes in handy. Bucket-brigade chips have limited headroom. Certainly enough to do the job under normal circumstances, but there's only so far you can push them, cost-free. Companding helps to keep the signal hitting the delay chip tame enough, and also assists in keeping noise levels low. Some designs use 'em, but most don't. While increasing supply voltage can increase usable headroom in a lot of other things, it doesn't do as much for delay chips in particular.



> Is there actual Boss LED lights that I can get? Adding things to the circuit is more than I am comfortable with...


There wouldn't be all that much to add. The specific current-limiting resistor is easy enough to spot. If you look at this board image, it's the one labelled 3.9k in the black and white parts layout, over on the left hand side, halfway down the board, going to solder pad 13. In the photograph, it is standing on end, beside the big capacitor. As long as someone has the right, ahem, size of soldering tip (little in-joke, there), it should be easy enough to safely remove and replace. Alternatively, since there is a wire going from solder-pad 13 to the LED, a person could just leave the 3.9k in place, and try out different resistor values between solder-pad 13 and the connecting wire, until you found one that suited the amount of illumination you wanted for the LED you bought. As suggested earlier,a total value i the range of 3.9k up to around 22k (combining the onboard and additional) is a safe bet to get you in the range you need. Once you find the optimum brightness, THEN you can replace the one on the board.

I doubt one would be able to easily obtain an "actual Boss LED", but if you can score one of the old school 3mm red LEDs - likely to be in the 600mcd range - you should be fine.


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## Sneaky (Feb 14, 2006)

Just curious if you tried it with a battery. My old CE-2's LED didn't light up using it with a Rockett 9VDC power supply but it worked fine with a battery.


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## mhammer (Nov 30, 2007)

I'm assuming you mean it didn't work at all with an external power supply, rather than it worked but the LED didn't light up?


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## Guest (Jun 30, 2015)

The pedal works, the LED does not. I did try it with a battery.


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## mhammer (Nov 30, 2007)

OK. I dug around and found this interesting little bit of history and insight into the PSA vs ACA adaptors: http://stinkfoot.se/archives/726

If the pedal itself works, but the LED doesn't (or rather, is so dim as to not clearly differentiate between on and off), perhaps the solution - assuming one is going to use the same power supply - is to increase the current feeding the LED. So, if you have a 10k resistor on hand, try and solder it in parallel with the existing 3.9k resistor I mentioned earlier. The two in parallel will yield a 2.8k resistance. This will increase the current feeding the LED. It won't make the thing bright, but should yield a detectable change in brightness in effect vs bypass mode. Make sure the room is relatively dim, but if I'm right, you should be able to see it.

On the other hand, all of the above pertains to using an external supply, and you indicate a battery doesn't do the trick either, which suggests that either the LED is fried, or the diode in series with it is fried as well.


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## knight_yyz (Mar 14, 2015)

MCD has nothing to do with how much current the LED needs. What you need to know is the forward voltage. IE how much voltage does the LED require to attain the advertised number of MCD's. Most LED forward voltages are the same assuming the same size and shape. If the LED is running on a 12v circuit it will have the proper resistors to run at that 12 volts. So if you pull a red LED and put another red LED of the same size you should be good. Even switching to another color will be good as long as the forward voltage required is at least the same as the old one or more. If the new LED needs more juice than the old one it will be a bit dimmer. Most LED's need about 2 volts give or take, some need 3 or more. SO if you pull a LED requiring 2 volts and the circuit is setup for 2 volts then putting an LED with a forward voltage of 1 volts will burn out the LED sooner than expected. If you pull that same LED requiring 2 volts and replace it with one that required 3 volts, the new one will be dim due to the lower voltage the circuit is putting out. 

If you swap an LED make sure the polarity is correct. There is an anode and a cathode and if you solder it in backwards it will not work. 

I know a lot about LED's as my car is full of them. My latest LED project was to take all my post lights in the backyard and convert them. The old LED's and batteries were toast. So instead of replacing 10 post top solar LED lights at 50 bucks a pop, I bought 20 rechargeable batteries and 20 blue LED's for a total of about 25 CDN. 

crappy cell phone pic


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## mhammer (Nov 30, 2007)

You're right that the mcd unit of measurment is not a measure of how much current is required. It is a measure of how bright the LED will be with a given voltage and current. If one was trying to light up a yard, or a stairwell (as I do by removing the modules from those solar garden lights and sticking them in the stairwell window), then the mcd-rating and a suitable power supply are what you want to know. Status LEDs on a pedal, are another thing, though, since you want *suitable* illumination, not _*maximum*_ illumination.

The LED in the pedal is going to get the supply voltage the pedal gives them, which will be 9v in the the vast majority of cases. Any pedal that uses true-bypass switching will most certainly feed the LED 9v. At 9v, with nothing to drop the current, the LED will fry in seconds. I've done it far too many times for my liking. Dropping the current with a series resistor is required. The value of that current-limiting resistance is a function of how bright you want/need the LED to be. If it is an older low-efficiency one, then the resistor value will be lower, in order to bring the LED up to usable brightness (without frying it). If it is a significantly more efficient "superbright" variety, then the amount of current needed to achieve a usable brightness is drastically reduced.

One of those superbright blue LEDs, like you show, will work just fine as a replacement in any Boss pedal of any era. The stock current-limiting resistor (usually between 1k and 3k9) will keep it from burning out on power-up. But you wouldn't want to look down at your pedals when they're on, because you'd be seeing afterimages when you looked up again, and likely fall off stage like Dave Grohl!

Many people will complain that the LEDs on their pedals are too damn bright. The answer is: increase the value of the current-limiting resistor to move it a little farther away from its maximum mcd-rating.


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## greco (Jul 15, 2007)

mhammer said:


> ....the LED will fry in seconds. I've done it far too many times for my liking.


And doesn't that smell wonderful!

Cheers

Dave


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## knight_yyz (Mar 14, 2015)

Whether the circuit is 9v or 12v, the pedal should be set up to run that LED at optimal. ( well not really because limiting the LED with a resistor is very crude compared to what you can do with say an LM-317) I would look for 1000MCD LED's if you don't want really bright ones. I don't think you can get red LED's with less than that rating. I'm assuming most pedals are using red? (I don't use pedals yet. I'm still concentrating on learning to play and not finding my sound.) 

BTY the blue LED's in my post lights are 5mm but only 9000MCD but there are 2 LED's each. You can get 3mm white at 35K mcd!

A red, orange or yellow LED will most likely require 2.2-2.8V, Blue, green, white, pink or UV requires 3.2-3.8V. So if you have a blue/green/white/pink/uv LED and want to go to red orange or yellow you need a bigger resistor.


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