need power LED help... Boss RV-3

[crittoprrr]

I don't know if anyone has a schematic at all, but I have a Boss RV-3 with an ill-behaved LED. When the pedal is in bypass, the light dims, but is still visibly lit. Don't like that. It's brighter when activated, sure, but I would rather it be OFF when the pedal is off. I've been trying to figure it out, but no luck yet. So any input deeply appreciated.

[ayayay!]

Are you using a battery?

[Fender56]

http://www.schematics.ca/uploads/PDdownloads/boss_rv3_delay_reverb.pdf

[andrew_k]

You don't want an RV-3... You want to sell it to me 

[crittoprrr]

A: I use an adaptor not batteries...

B: Funny you should ask about selling...I really only wanted to fix the thing up so I could sell it and get a decent delay pedal instead. I've only ever used the delays on the thing anyway. So if we can come to an agreement I'd be happy to sell.

But hopefully I can get this LED fixed first.

[andrew_k]

crittoprrr has mysteriously lost his inspiration to find a solution to this at the same time as I have gained the need to find a solution. 

From the schem it looks like the LED is getting its positive current from pin 5 of IC10, so if IC10 is the cause of the misbehaving LED there probably isn't much hope outside of replacing the IC?

Can someone else please have a quick look and offer a more educated opinion than I?

[edit]It seems the IC in question, an M37470, is a Mitsubishi chip and is still available... well, from china at least, and in batches of 2000 
Being a taiwanese-made pedal, it's probably SMD and therefore waaaaaay beyond me to fix. At least the potentially bad IC isn't one of those Roland/Boss proprietary ones!

[darron]

andrew, I thought that you had some sort of theory going. i have a boss hm-2 which i hardly ever use. the LED on that glows dim when in bypass also, but not on battery. I replaced the led with a high intensity blue one from the regular red. i don't recall ever noticing it with the original red led. maybe it was designed to always trickle a bit that you can't actually notice on the original led.

is it the stock led?

by the way... i haven't looked at the schematic as i'm about to go to sleep as soon as i post

[crittoprrr]

I should say the I changed the LED to a large white one.

[andrew_k]

I think you've unearthed the cause Darron. Could it be that the replacement LED requires a larger limiting resistor to prevent it from lighting?
I'll test that theory when it gets here and let you know. I replaced the red LED in my DD-3 with a 3mm white one and didn't have this problem 

[slideman82]

It seems the IC in question, an M37470, is a Mitsubishi chip and is still available...

Isn't this IC a microcontroller that has to be programmed? I've got some sort of problem, bypass doesn't work, just the clean signal, but, when you plug the 9V battery, the effect sounds about half a second, so it works in the transient! I hope this bug isn't burnt... I have unsolder both bypass JFETs and make some jumpers between D and S, but the problem stills there... could the problem be the SMD bipolars that are connected to those JFET's?

[The French connection]

A: I use an adaptor not batteries...

Hi!
Is your adaptor is an ACA or PSA Boss adaptor? I've read somewhere that there's an issue with Led and proper adaptor...Try a battery just for fun...

Dan

[caress]

i have an rv-5 which does the exact same thing when powered by an adaptor with too much voltage.  i had a supply which could switch from 5-7.5-9-12-15v, but i think it still put out more than it said. when i was on the 9v setting, it would glow when in bypass - switched it to 7.5 and everything was fine.  now i use a 1spot without any led glow issues...

[slideman82]

mmmmm this gives me an idea! Thanks!

[andrew_k]

Is your adaptor is an ACA or PSA Boss adaptor?

I now own the RV-3 in question; it's not the power supply (I've tried batteries). I think it has somehting to do with the 5mm ultrabirght white LED that has replaced the original 3mm red one. I've not bothered to try and fix it as the pedal works fine.