RAT: Clipping problem

[Unlikekurt]

Hello all.

I've got a rat clone built on a tonepad pcb.
Three way switch (on / off / on) for the clipping diodes.
My 3mm Red LED's won't work properly and i'm at a loss for figuring it out.  They act like jumpers or dead shorts.
I've proven that the switch is functioning by checking continuity between it and the board and in addition have placed 1N914's in both "ON" positions and they function perfectly.
Now, when i place led's in either "ON" position they will blink on ever so softly with the instrument signal when the switch is initially flipped into the corresponding position but then go out completely and do not turn back on.  I've also ruled out that the LED's themselves do not work properly by placing them into another RAT clone (built at the same time and in the same manner without any complications regarding this issue).

Any thoughts as to what I should look at or into?

Thanks a million

James

[LP Hovercraft]

I'd verify that the two LEDs meet the following conditions:

First, verify that each LED is good via a multimeter.  If not, replace the LEDs

When the switch has selected ON for the LED clipping-verify that exactly one anode and one cathode of each LED is connected to circuit board ground with a continuity tester.  Also verify that the corresponding cathode and anode (the lead of each LED that's not connected to ground is connected between the filter pot and the 1k resistor after the opamp's output with a continuity tester.

It does take a bit more signal out of the circuit to make an LED conduct and clip.  I've had some LEDs that will do their job of clipping and not even give off any light. Is it distorting or just boosting the signal?

[Kesh]

Are you sure they act like jumpers? Shorting everything to ground and killing the signal?

[Pyr0]

Check the polarity of the 4.7uF elec capacitor just before the clipping diodes.

[kurtlives]

Hello all.

I've got a rat clone built on a tonepad pcb.
Three way switch (on / off / on) for the clipping diodes.
My 3mm Red LED's won't work properly and i'm at a loss for figuring it out.  They act like jumpers or dead shorts.
I've proven that the switch is functioning by checking continuity between it and the board and in addition have placed 1N914's in both "ON" positions and they function perfectly.
Now, when i place led's in either "ON" position they will blink on ever so softly with the instrument signal when the switch is initially flipped into the corresponding position but then go out completely and do not turn back on.  I've also ruled out that the LED's themselves do not work properly by placing them into another RAT clone (built at the same time and in the same manner without any complications regarding this issue).

Any thoughts as to what I should look at or into?

Thanks a million

James

Your pedal is working perfectly normal.


The LEDs will only light up when your guitar signal meets or passes the LED's clipping threshold voltage (probably around 1V depending on what LEDs your using).

[Unlikekurt]

kurtlives: no not normal.  it isn't clipping the led's.  regardless of the strength of signal / setting of the distortion potentiometer.

pyro: 4.7uf is installed correctly.

kesh: that was an error on my part.  they act as though they are not there.  yet when the 1N914's are in, they work as expected.

LP: as stated i verified the LED's are good by checking them in another rat circuit.  Also i checked the functionality of the switch with my multimeter and found it to be in working order. 

[Pyr0]

If the leds aren't clipping, then there might not be enough output from the opamp.
Did you use a 10k pot instead of a 100k for the gain control ? Check other component values near by.

[kurtlives]

Check to see if your 4.7uF cap is installed correctly and not leaking DC.