Helpme troubleshoot JFET switching

[DIY Bass]

I am getting quite familiar with this schematic :-)

I am getting effect signal through without a problem.

I am getting no bypass signal through.

The bypass signal is present on one side of Q2, but not the output side. (obviously with the pedal set to bypass - or at least with the red light off :-) )

I have measured 4.5V (relative to the gnd power supply) on the source and drain of both Q2 and Q3.

Both gates measure about 200mV.  Neither gate changes with the bypass switch, but the effect sound is present when the light on, and there is no sound at the output with the check light off.  Do I just replace Q2?  Could there be something wrong with the flip-flop?  I have no idea even what to be looking for.

[Prehistoricman]

What's the voltage of the Q2 gate in normal and bypass?

If you suspect Q2 may be broken, swap it with Q3 and see if the problem is still there.

[duck_arse]

try shorting source and drain of Q2, see if signal gets past. if the check light toggles w/ bypass switch, the flip flop should be OK.

[Slowpoke101]

I agree with duck_arse. If the check light toggles on and off (reliably ) then the flip flop is fine. Definitely try shorting the source and drain of Q2 together - it should now pass the bypass signal. I do suggest checking that C25 is not shorted and that R31 is not open circuit. Test D1 as well. Q2 is most likely the problem but do look for solder bridges and damaged tracks as well.
Measuring the gate voltages can be misleading due to the input impedance of most multi-meters. It can be low enough to turn the JFETs off. If you want to confirm that the gate voltage is switching with the flip flop measure the voltage on the cathode end of D1. To turn the JFET off the gate voltage must go lower than the voltage present on the source (usually - theses things are sort of uni-directional when it comes to the source and drain connections ).

[DIY Bass]

Replaced the FET and it all works fine now :-).  I ordered (and used) what was specified in the schematic (2SK118-O) rather than what turned out to be in the board (K30A) but it all works fine, which is the desired result.