Boss Bass Chorus CE-2B LED question

[wildebelor]

So I've been asked to rehouse this boss chorus that was really old and grungey, footswitch was dead, wasn't grounding etc. Everything has gone smoothly except one thing.
When I replaced the LED (old led worked fine however it was replaced due to the size), the new one doesn't light up - even when the effect is working and engaged.
I thought oh silly me, the LED's resistor is clearly incorrect - So I swapped out R51 (3.9k) for a 390 ohm.  Still no luck.

This is a schematic and board layout here http://www.hobby-hour.com/electronics/s/boss-ce2b-bass-chorus.php

I'm a little puzzled!

Thanks!

[PRR]

> the LED's resistor is clearly incorrect

Why?

More likely wired backward.

[wildebelor]

I put this down as I had other projects to tackle but upon returning to this, I have come to the conclusion that I must take into account the zener diode when calculating which resistor to use for the LED?
Is that correct?

[PRR]

If it is not lighting at ALL, the LED is backward (or dead).

If it lights "dim", the resistor could be smaller.

> take into account the zener

Well, that's why BOSS paid its engineers the big Yen, to pick a good resistor, right? And it did work before. And while LEDs do vary a little in brightness for current, it should "glow" even if dim. No light really suggests wired backward.

-OR- you replaced a red LED with a white one?

[petey twofinger]

the older model boss pedal (aca  is the number for the P.S. ) ran on 12 volts for the power supply , but still used a 9 volt battery .

IF     , one has an older style 12 volt ACA type adapter power supply boss pedal , it isnt too challenging to JUMPER over ( bypass )  the resistor to enable it to fuction properly with a 9 volt power supply or P.S.

there is a resitor and a diode for the led to drop the power for the led , initially the boss aca ps put out something like 14 volts with no load , so if one bypas' this resistor , the led will light with a mere 9 volts .


i did this on a CE2 i got for a quarter at a garage sale , initially , the effect functioned properly , but the led was not lit , or actually very very dimly glowing . i think , if memory serves .

i am going to take the easy road and post a single link , but i am sure one could find a few more how too's for this not so rare modification .

http://jorgezorro.blogspot.com/2009/12/boss-aca-to-psa-power-supply-mod.html

i seem to remember it being a single resistor swap on my ce-2 but this was years ago , and i cant not remember ...


good luck sir .

[petey twofinger]

http://hugeracksinc.com/forum/viewtopic.php?f=1&t=21764

[wildebelor]

It's funny, I just assumed it was 9v because when I plugged it in - it worked!

[petey twofinger]

yeah i had this same situation and ran that chorus for a while then it dawned on me , ... there is a reason that led is not on so i googled and read up on it . i was a bit nervous as i always am when opening up something , but it isnt too difficult of  a mod . i changed out the led for a different color as well , which was proilly a bad idea for the resale value as it is an older model but ...  i can always chop in the ugly red one at any time , it looks great with the pale blue one thats in there now .