RMC wah heeeeeeeeelp

[mesfigas]

Hi guys i own an RMC wah ..the wizard one and las night i burn by accident one of the resistance on the pc board of the pedal
the resistance is numbered  ( R29 )  but i don know how many kohms it is
i think it is 0.47kohm but i am no sure.
if someone has he same wah wah pedal please tell me cause here is no manual for this pedal.

R M C owners please help me

[ToneMonkey]

Should have differnt coloured rings on it.  These give you the value.

2 minutes on the net and you'll work out the value.  I'll try to find you a link.

EDIT: http://www.breakup.de/resources/resistor.html

[mesfigas]

Should have differnt coloured rings on it.  These give you the value.

2 minutes on the net and you'll work out the value.  I'll try to find you a link.

EDIT: http://www.breakup.de/resources/resistor.html

The resisor is burned there is color to identify.
there are some residtors near the burned one and have same color
i think it is 0.47ohm
if it is not  is there going to be any problem to the board or just a sound difference  ???

[mesfigas]

the upside of the pc board is a little burned but the downside is o.k
i put a 047 resistor and a 022 resistor but i  hear nothing from he pedal
i think the pcb is o.k but no sound   shite!!!!!!!!!!!

[noodleplugerine]

If the resistors you put in are too large then you might not hear anything.

If the resistor you're setting up is part of a potential divider and it's too low, you might not hear anything.

Basically - Find out the colour of the rings on the resistor, and then show us.

[mesfigas]

If the resistors you put in are too large then you might not hear anything.

If the resistor you're setting up is part of a potential divider and it's too low, you might not hear anything.

Basically - Find out the colour of the rings on the resistor, and then show us.t

the resisor is burned i dont see color its all burned

i send an email to the manufacturer i hope to answer.

[HananR]

Hey man.
I got the same problem.
R29 is burned out and I cant tell the original value.
did you ever solve this problem?

thanks!
-H

[sjwebb90]

I haven't seen any such resistors as low as 0.47 ohms in a wah before although I am not familar with RMC wah.
However, stating the obvious if it burning out its obviously drawing too much current!

A trawl of the web come up with a site shoing the innards of RMC Wizard wah with componet values. There is reference to 4.7K 470K and 4.7M
http://www.effector-repair.com/index.php?main_page=RMC_WizardWah

You could always email RMC and ask them what it should be, there maybe a requirement for an upgraded resistor
http://www.realmccoycustom.com/

[jpfamps]

How did this happen?

The resistor will have burnt due to over dissipation.

This would imply that something inappropriate has happened to the unit, ie the wrong power supply has been used.

If this is the case it is possible that other components will have been damaged as well, so you may need to get the pedal looked at.

[Le Chat Noir]

The same has happened to me yesterday as the above posters - a friend of mine borrowed my Wizard and tried to use a center positive power supply. Result - black smoke, fried R29 :( Did you guys ever fix this?? I've found internal gut shots of the Wizard, but not my one, must be older ones and it's hard to tell which bit is which :(

[Le Chat Noir]

Here's a pic I found somewhere of the board... it's hard to tell but isn't that brown-black-black-gold-brown = 10 ohm?

http://www.lechatnoir.org.uk/r29.jpg

[jpfamps]

It's a 4 band resistor, and looks like 10 ohm (or 17 if the second band is violet).

OK, without seeing the whole circuit my guess is that this resistor is connected to the +ve rail and forms an RC filter with C27 to reduce ripple on the +ve rail.

D21 is a reverse biased diode connected from the +ve rail to ground. In normal operation this will not conduct. However if the polarity is reversed this conducts and shorts the power supply out through R29 destroying it (as you've found out).

This is sometimes refered to as a crowbar protection circuit. Essentially the resistor (and possibly the diode and the wall wart) are sacrificed to protect the rest of the pedal.

I would replace R29 and D21 (making sure the polarity is correct!!!) and I'm fairly sure your pedal will be fine. This is not a difficult job should be within the capabilities of anyone with some soldering experience. Replacement parts can be got from Maplin electronics if you have a branch near you.

The value of R29 is not critical and any value from 10-100 ohms will be fine.

[Le Chat Noir]

Thanks a lot for your reply jfamps, it's really kind of you to help out! I suspected it must be some kind of protection mechanism, but my knowledge of electronics doesn't extend that far. I can solder and build pedals to instructions, but don't really understand what's going on in there too deeply ;) There's a Maplin about half an hour from me so I'll probably pay them a visit next week. Thanks again, I'll let you know if I get it sorted!

[Le Chat Noir]

SUCCESS! Went to Maplin today and bought a 10 ohm resistor for 16p. I took the pedal in and the guy tested the rest of the circuit with a multimeter to make sure nothing else was fried. Got home, soldered in the resistor, and operation is back to normal :) Hope the other two above who were having problems find this helpful! Thanks again to all those who contributed above.