Boss Oc-2 - Relay based true bypass using stock flip-flop switching?

[anticpunk]

Hey,

So a guy I know, a firm believer in the "everything needs TrueByPass" idea, dropped his OC-2 off to me.

I've done the searches and turned up alot, but unfortunately nothing that really explains the solution for what I'm trying to do.

Basically I need to lock the wet signal on and kill the bypass(dry) signal, and then make the F/F control the Led and a Relay.

I have some 9V Dpdt mini-relays that I had hoped to use but from my experiments I've realized that the boss F/F doesn't produce enough juice to run them. With the fets on, I'm getting high mV to low Volts.

I've done 2 Arion SCH mods which involved the jumping of solder pads to omit Fet function, so I guessed that it was the same avenue.
It looks to me, based on the original schematic, that Q3 and Q4 control the wet/drive switching. I tried ommiting Q4 and jumping out Q3 which gave me dry signal only. I tried jumping out Q4 and ommiting Q3 which interestingly did the same thing.

A borrowed link to the schematic from an earlier thread:

http://s232.photobucket.com/albums/ee173/YSEADMV/?action=view&current=BossOC-2Octave.jpg

What am I missing? I know someone out there has to have done this, if not with a relay at least with a DPDT Latching switch. So how did you lock the circuit into wet mode?

Thanks for your time,

Jay

[R.G.]

Basically I need to lock the wet signal on and kill the bypass(dry) signal, and then make the F/F control the Led and a Relay.

No problem. The only issue will be that the relay coil needs big currents if it's a non-latching type and will eat batteries. A DC power adapter will work OK.

I have some 9V Dpdt mini-relays that I had hoped to use but from my experiments I've realized that the boss F/F doesn't produce enough juice to run them. With the fets on, I'm getting high mV to low Volts.

What you need to do is use a small MOSFET like the BS170 or 2N7000 to drive the relay. You would hook the gate of the MOSFET to the side of the flipflop which does NOT power the LED. That collector is high when the effect is engaged (and the LED on) so it would turn the MOSFET gate on if the source were connected to ground. This could then pull down the end of a relay coil connected to +9V. Use a diode reverse-parallel with the relay coil so then the MOSFET turns off it does not damage the MOSFET by overvoltage.

I've done 2 Arion SCH mods which involved the jumping of solder pads to omit Fet function, so I guessed that it was the same avenue.
It looks to me, based on the original schematic, that Q3 and Q4 control the wet/drive switching. I tried ommiting Q4 and jumping out Q3 which gave me dry signal only. I tried jumping out Q4 and ommiting Q3 which interestingly did the same thing.

Q3 and Q4 do indeed do the wet/dry switching.

Tie the band end of D5 to ground. Disconnect the end of R28 that goes to the collector of Q5 and connect it instead to +9V. These changes make the signal path permanently "on", but leave the flipflop and LED working. Then do the MOSFET thing to drive the relay, and hook up the relay contacts like your favorite true bypass DPDT.

[anticpunk]

R.G,

Thanks so much for your wisdom! The only thing I am confused by is the Diode reverse parallel you referred to. Do you mean 2 diodes connected anode to cathode side by side, like a diode pair in a fuzz pedal? Maybe I'm thinking in the wrong direction. Just 2 diodes to control the voltage direction?

Basically the flip-flop feeds the mosfet which is gating the negative side of the relay coil. Am I following correctly? So the source would connect to ground, the gate to the F/F and the drain to the diode and on to the relay coil?

Sorry for my redundant questions. Thanks for the reply.

-Jay

[R.G.]

No, only one diode parallel with the relay coil. It's in the direction where it's normally reverse biased when the relay coil is turned on. The purpose is that the relay coil's inductance causes a reverse voltage spike by inductive kickback when you try to turn it off. The diode clamps that reverse voltage spike to the power supply and keeps it from breaking over the MOSFET or other driving device with high voltage.

If the relay is connected with one lead of the coil to +9 and one lead to the MOSFET drain, the diode's band/cathode connects to +9 and its anode to the MOSFET drain.

Yes, the flipflop controls the MOSFET, which pulls the relay coil down to nearly ground. The connection is as you say, drain to relay coil, source to ground, gate to FF.

[anticpunk]

R.G,

Again, Thank You. The diode makes perfect sense, I was just misunderstanding the application.

I ordered the Mosfet and anticipate no further trouble.

Many Thanks,

Jay