Danelectro switching and true bypass

[ExpAnonColin]

After some searching it is fairly clear to me that there is some amount of confusion that ensues when someone asks about danelectro switching and the proper way to make it true bypass.

I have worked only with bypassing mini pedals, and all but the PB&J have used the same switching board (good move danelectro!).  The switching involves a bit plastic non-latching DPDT, but it is simply being used as an SPDT, which is used to trip a flip flop, which then switches a 4053... being used as a DPDT in this case, to bypass or unbypass the pedal.  The 4013 also provides a signal for the LED's on/off, as the LED is always on the other circuit board.  There are a variety of kludgy methods involving forcing the electronic switching into the non-bypassed state at all times, either by simply relying on the pedal to "turn on" as soon as power is applied, or by jumpering the switch, or by cutting some traces on the flip flop and hardwiring, so that the coontrol for the 4053 switching is always non-bypassed.  I tend to not like those methods... I always feel dirty using them, because you're leaving so much in tact that can be removed!  A whole circuit board, in fact.

Each dano mini (other than the PB&J) has 6 wires from the switching board to the effect board.  Not all of them are used all the time!  This is a sacrifice danelectro had to make when they decided to do one switching board.  The wires, in order starting with the one closest to the input jack, go (color may vary... but I haven't seen it do so)
Send (blue)
9V (green)
Ground (yellow)
No-bypass Send (orange)
Return (red)
LED control (brown)

No-bypass send is essentially a wire that always contains the input signal, regardless of whether the effect is bypassed or not.  It's used in some pedals (just the chicken salad as far as I know) and not in others.  If you look at the effect board and it is not connected to anything, you can just cut that wire.  LED control you can also ignore in any case, because you will be using your 3pdt for the LED on/off.  So that leaves you with a simple set of connections on the effect PCB to connect your 3pdt to... almost.  There one caveat is that on the switching board, all of these are biased to Vref...  (as far as I can tell-the last time I did a TB to a non-PB&J mini was very long ago... but I am about to do another and will report back).  So you will need to do the standard referencing...  100k to V+, 100k to ground, a cap with the negative end to ground and the positive to the junction of the resistors, the junction then connected to two 1meg resistors, each individually connected to .1uF caps, connected to the input and output... after the .1uF cap, you go to the switch.  Sort of a pain... I have not tried ignoring the bias but it might be possible.  It's up to you in the end whether it's easier or not to kludge the bypass.

For the PB&J, it's a bit different... you cannot remove the switching board because the switching is on the same board as the delay chip!  The three boards are switches, effect, and buffers.  There is no real way to get around using the buffer board.  The switches you can get rid of.  My current favorite way to do true bypassing, while retaining the ability to select long or short, is to cut legs 2 and 5 on the tiny SMD 4013, and then make a little jumper between legs 10 and 8.  Then, just do the TB to the jacks on the buffer board.  You can also simply use a DPDT for long/short...  take a look at the schem, you just ahve to cut a trace and switch a leg on the PT2395 between high and low, using the other throw of the switch for the LEDs.  The LED in the PB&J is a 3-leg two color LED, with a common anode (the center lug).  I just use the 3pdt to switch the center lug on and off, wiring two LEDs with their anodes connected and wired to that 3pdt switch's lug, and wiring the cathodes to the PCB.  Either way works dandy.  If you are really good, you'd make a new buffer board-the PB&J has a few very silly things, one of them being that the op amps are powered with 5v of headroom when 9v is available.

Good luck...

-Colin

[sevenisthenumber]

Have you done this to a tuna melt??
Great stuff!!

[Andre]

Here's the schematic diagram of the RockyRoad Input/Output board.



I'm in the process of rehousing and true-bypassing my RockyRoad.
The true bypassing should not be a problem.
The one thing I have to find out is how to switch on the effect on power up.
I guess I will have to use some RC combination to create a sort of delayed pulse, since after powering up the pedal it takes some time before you can
switch on the effect.

André

[jefe]

I like Dano's approach: just replace the original stomp switch with a nice offboard momentary switch, call it the "arm" button, and be done with it. You only have to hit the arm button once when you first power the pedal up.




edit: no, wait -  I'm not sure if it would work that way. You may have to hit the arm button every time you switch the unit off. Either way, I like the simple approach. I'm thinking about re-housing my Chili Dog, but not for true bypass, just replace the stock momentary switch with a nice stomp switch.

[danielzink]

Having just rehoused a Danelectro Chicken salad:


http://acapella.harmony-central.com/forums/showthread.php?t=1718263&page=3


Through page 5.

My rehouse:

http://pws.cablespeed.com/~danielzink/salad.htm


We found that the orange wire from the Dano board was 4.5v back to the effect board. We built a simple circuit from 9v to 4.5 and everything works like a charm !!

Dan