Author Topic: Dead Muff (Read 2654 times)

badgermark · « **on:** December 05, 2007, 04:55:25 PM »

So I was modding my NYC Big Muff and it died on me.

I was replacing the clipping diodes with LEDs, stuck in my LEDs and put everything back together and nothing happened. Put the diodes back in place and it was still bricked.

Sound comes through when the pedal is off, turn it on and the LED lights up but no sound at all. Everything looks ok to me, checked my wires to the switch and stuff and everything is in position, no breaks in the PCB either.

What could be the problem?

HTH AMPS · « **Reply #1 on:** December 05, 2007, 06:55:01 PM »

Check the offboard wiring - it's fairly common for wires to break off when you're modding pedals.

I'd check for solder shorts between traces around the area you've modded.

Failing that, knock up a test probe... one 1/4" jack socket, two wires (one live and one for ground reference) and solder a 0.1uF cap to the free end of the live wire and a croc-clip to the free end of the ground wire.

The test probe goes on the output side. Clip the ground wire to the ground point on the input jack, then use the live wire side with the cap attached to follow the signal from the input through the circuit. When you get no sound you've found your problem.

Also, take voltages at the supply point to make sure you're getting 9v into the pedal. Also take voltages at the base, emitter and collecter of each transistor to make sure each transistor is 'on'. You want the emitter to be above the base by around 0.7v (turn-on voltage). If not, it will be mis-biased and you'll either get no sound or a splattery type of fuzz that only sounds when you whack the strings really hard.

:twisted:

badgermark · « **Reply #2 on:** December 05, 2007, 09:55:37 PM »

That's exactly what I needed, I noticed the offboards came off dead easy, but everyone got put back where it belongs. Shall bust out the multimeter tomorrow, question, how do I use it to test a circuit?

machine_of_god · « **Reply #3 on:** December 05, 2007, 11:05:07 PM »

All multimeters have a setting that tests whether there is an unbroken connection between the 2 points. So you put one of the points at the beginning of the curcuit you're testing, and put the other one at the END of the curcuit that should be continuous and unbroken. Then the machine will beep, or something.

Either way, it'll show you whether there is a connection or not. Easy 8)

Unless of course I didn't understand what you're trying to achieve... I tend to only read half of what's written :roll:

badgermark · « **Reply #4 on:** December 06, 2007, 02:10:37 PM »

So I had another look at it today, and I have no idea about how to use a multimeter though. Interesting point, touching the back of the circuit board under transistors 1 and 4 allows some signal through, it's loud yet clean. So ordered some new trannies. Odd seeing I was modding nowhere near that side of the board...