Boss DF-2 ON/OFF problems.

[Samy]

Hi !
I have one DF-2 to fix it, the problem seems to be in the on/off circuit.
When i press the switch i have the fx working with the feedbacker and the led blinking, but i must have the the switch allways pressed or the pedal will turn the fx off.
I have some difficulties to identify the bypass circuit since it's different from others, and theres is a important detail that i have read in Bossarea :
"# To change the function mode from Normal, Distortion and Feedback, simply depress the pedal
# The Distortion effect is switched on and off by short-stroke depressing of the pedal
# Pressing the pedal down further engages the Feedbacker function and the sound lasts as long as the pedal is depressed."

Thanks.

[Samy]

This problem is pissing me off !    ( sorry my bad temper )

The schematics can be found here: http://experimentalistsanonymous.com/diy/Schematics/Distortion%20Boost%20and%20Overdrive/  and here : http://filters.muziq.be/model/boss/compact/df2

Any helpful tip on this one will increase your good karma points ! 

This switch circuit is very peculiar, i have never found one like this in any other pedal. If you check the schematics you can see one IC HD1400  ( a logical circuit ) that i don´t fully understand. The on/off must work like described above.
I have replaced the momentary switch but the problem remains, i´m thinking in replacing the electrolytic caps on the bypass area because something is turning the pedal off ... maybe a bad cap, maybe a bad transistor , i don´t know .

[Mark Hammer]

The 4001 chip is CMOS, and more than likely one of the most "fragile" on the board.  They can take up to 15v supply voltage, but are usually happier when working with 5v and normally designed around that.  Since it appears there is nothing wrong with the octave-up "feedback" circuit, that implies that both the 4013 and 4046 are working normally. Since there is the problem of needing to hold the foot treadle to prevent shut-off, there appears to be nothing wrong with the 4066 either, which leaves only one CMOS chip potentially damaged - the 4001.  Happily, these are easily found and dirt cheap.

[Samy]

Thanks Mark !

I have new info to add..
I have checked the voltages and something is wrong. Between the DC jack ground to pcb ground i have 3,15V, when measuring from the DC jack + to pcb ground i have, logically, around 6,75V. I presume something is sending 3,15V to ground ... weird.
I will check the C23 filter cap and the C19 right after the DC jack and i will remove the HD4001 to see if the voltages goes to normal ( ground at 0V ), i will check the IC availability around here also.