Broken Effects Pedal / help please

ChrisPbass · #1 09-05-2011, 03:45 PM

I have a Maxon OD820 that toakes a 9 volt adapter only. no batteries.

long story short...I accidently plugged in a 18volt adaptor.

now...no work.

The led/light comes on but when the pedal is pushed in..nada...no noise, nothing. It's basically a big mute switch.

Any advice, thoughts? New paper weight?

runmikeyrun · #2 09-05-2011, 04:43 PM

A number of things could have went wrong but I need to see a schematic first. Do you have a multimeter so you can check voltages?

How long was it plugged in for? AC or DC? Was at least the polarity correct?

If you're lighting the LED, then you probably didn't fry the protection diode or you wouldn't get any power at all. You might have cooked a chip that's meant to run on less than 18v. You could have also blown a cap, the electrolytics are probably only rated to 16v.

I found a schematic, but for some reason i'm blocked from looking at it. If you can download it and post here i'll try to help.

freestompboxes.org • View topic - Maxon 820 schem, anyone ?

runmikeyrun · #3 09-05-2011, 04:51 PM

Just found this on the Maxon website...

While the OD-820 accepts 9 volts coming in, it then uses a DC-DC voltage converter (#MAX1044) to bump this up to 18 volts.

So by plugging in 18v you put the pedal voltage to 36v. You could have also popped something in the voltage converter circuitry.

do you feel experienced enough in electronics to tackle this?

ChrisPbass · #4 09-05-2011, 04:51 PM

Quote:

Originally Posted by runmikeyrun

A number of things could have went wrong but I need to see a schematic first. Do you have a multimeter so you can check voltages? I have a multimeter, but use it as a battery tester so be gentle....

How long was it plugged in for? AC or DC? Was at least the polarity correct? correct polarity and minutes...

If you're lighting the LED, then you probably didn't fry the protection diode or you wouldn't get any power at all. You might have cooked a chip that's meant to run on less than 18v. You could have also blown a cap, the electrolytics are probably only rated to 16v.

I found a schematic, but for some reason i'm blocked from looking at it. If you can download it and post here i'll try to help.

can't open that schem either...searching

freestompboxes.org • View topic - Maxon 820 schem, anyone ?

_____________

ChrisPbass · #5 09-05-2011, 04:52 PM

Quote:

Originally Posted by runmikeyrun

Just found this on the Maxon website...

While the OD-820 accepts 9 volts coming in, it then uses a DC-DC voltage converter (#MAX1044) to bump this up to 18 volts.

So by plugging in 18v you put the pedal voltage to 36v. You could have also popped something in the voltage converter circuitry.

do you feel experienced enough in electronics to tackle this?

I really am not all that experience w/electronics...
but today is a new day :

ChrisPbass · #6 09-05-2011, 04:58 PM

I don't think Maxon allows schematics to be public. There are none on diyforums.

runmikeyrun · #7 09-05-2011, 05:00 PM

hmmm. you may want to take it to a tech. You're going to be reading a schematic (if you can even find one) and checking voltages on components. You'll need to know what those components are and how they work. You'll also need to check for short and open circuits with your multimeter. If you think you are up to it, give it a go. Otherwise you're really just wasting your time and could make things worse.

ChrisPbass · #8 09-05-2011, 05:05 PM

OK thanks. Do you know of a pedal repairman?

Fredenando · #9 09-05-2011, 05:06 PM

runmikeyrun · #10 09-05-2011, 05:08 PM

Not in VA... but any place that repairs guitar amps should be able to do it. I can't imagine it costing that much to fix. Good luck buddy.

Skrogh · #11 09-06-2011, 08:10 AM

My guess is that the MAX1044 got fried.
The LED is hooked up to the battery, therefore still working.
The MAX1044 is ratet for a maximum input of 10v. They should run fine on 12v, but 18v? I doubt it.

But since you don't seem to have any experience with electronics, I'd say take it to a tech.

Darkglass · #12 09-06-2011, 08:26 AM

I agree, on the MAX1044! Do you have gut shots? if the IC is mounted on a socket, should be fairly easy to replace!

Best Regards

Doug.

ChrisPbass · #13 09-06-2011, 08:46 AM

I'll take a pic and update. thanks for the help!

Darkglass · #14 09-06-2011, 08:52 AM

Quote:

Originally Posted by ChrisPbass

I'll take a pic and update. thanks for the help!

You're most welcome! Let's hope the chips are mounted on sockets... then replacing any of them should be fairly easy.

ChrisPbass · #15 01-28-2012, 01:09 PM

Cast <ressurection>
>Success!

so...when I open the board I see the bottom of the PCB (?). I see the traces but the components are on the other side of the board. The board is firmly fixed. It's not budging and I don't see how it's held in.
Do I need to take the knobs off? Are they holding the board in?

BogeyBass · #16 01-28-2012, 02:05 PM

most likely the board is held in place by the board mounted potentiometers.
So yes, remove the knobs and remove the nuts holding in the pots.

some knobs have set screws so check for those if its hard to remove the knobs, or some manufactures will put a little silicone on the knobs so they dont fall off.

so pulling the knobs can be tough sometimes, other times they pop right off.

ChrisPbass · #17 01-28-2012, 02:08 PM

Yeah these have set screws. Tiny lil things.

going by my rate of progress I will have them off by June.

ChrisPbass · #18 01-28-2012, 08:13 PM

the max chip appears to go through the board. I don't think it's on a socket. :-/
way beyond my soldering skillz

ChrisPbass · #19 01-30-2012, 01:05 PM

halp!

Pollinator95 · #20 01-30-2012, 02:14 PM

What sort of knobs does it have? Is it the Ibanez kind or the one with the flatter enclosure?
In any case, you could try de-soldering the pots. The problem is that I can only see two connections per pot.

I guess Douglas might be able to help since he is probably experienced in PCB layouts because of his pedals

.