True Bypass and Power switch

[vonFrenchie]

I have a Vox V847 (reissue most likely) and its great. There are a few kinks here and there but my main problem is the lack of true bypass. It uses a spdt or spst switch to change between wah and inactive. I was thinking I if used a 3PDT switch like the ones offered at Stewmac I could effectively have true bypass and a power switch so that power isnt being drawn from the battery when the wah isnt active.

If it were wired like this

battery (-) effect in effect out
ground guitar in amp out
empty wired together

Would that work... if you can make sense out of that?

[momo]

Hey vonFrenchie, check this out.... Im just about to do the mod myself,check in the effects section for the vox.Its got all you would want to know about the pedal .

homepage.ntlworld.com/s.castledine/greenfuz/index.html

Cheers!

[vonFrenchie]

Yeah I would say so. Except instead of having the black connector go to the battery it would head up to a pole on the bypass switch (which would be 3PDT) and then the center of the bypass would be hooked to the battery.

So the switch would look like this

The light blue wire was not visible on the original diagram

[vonFrenchie]

Is there any way I could set it up so instead of bypassing the pedal I can switch between wah and a volume pedal? That way I wont have to by a V850. I need a volume pedal because my Zoom GFS707 that I used as a tuner and volume pedal went out.

[sumgai]

vF,

The only way I can see to make your wah do double-duty as a volume control is to leave the circuit on at all times, and use the footswitch to go between the two functions. That's relatively easy to do (some finagling on the circuit board), but hard on the battery life, if you get my drift......

There's no easy way to get a true bypass, with power-off, and also institute a passive volume pedal at the same time, on the same footswitch - there aren't enough poles on this kind of switch to make all the connections that you need. However, if you're not adverse to a bit of digital trickery, you could implement a one-chip switching arrangement, needing maybe 10ma of power. That would fill the bill, and leave the battery with lots of life left in it.

Unless you're a starving student, it'd be best to spring for a separate, and truly passive, volume pedal. Providing of course, that you don't need the effects that you used to get from the now dead Zoom pedal. I haven't looked at eBay or craigslist for anything like this, I'll leave that to you, should you opt to go down that road.

HTH


sumgai

[vonFrenchie]

I see what youre saying. Thinking about it, Id rather go the seperate pedal route. I could have them set up so that i could push the volume forward during a solo and use the wah.

So should I ditch the battery switch idea too? I dont like having the battery on at all times. The way I modified the diagram (the image above) has the battery on when the wah pedal is needed then when its off its completely passive and bypassed.

[sumgai]

vF,

I see what youre saying. Thinking about it, Id rather go the seperate pedal route. I could have them set up so that i could push the volume forward during a solo and use the wah.

So should I ditch the battery switch idea too? I dont like having the battery on at all times. The way I modified the diagram (the image above) has the battery on when the wah pedal is needed then when its off its completely passive and bypassed.

No, controlling the battery is a good idea - why waste the battery power if you're not using it for a good reason? Or to put it another way, why replace the battery any sooner than necessary?

However, your diagram doesn't look so hot. Regardless of what each color means, I can dope out what you intended from the terminals on the two jacks. In point of fact, a bypass switch should take the signal from the input, and route it to the output, bypassing the effect. But you want, and all pedals should have, the effect circuit completely disconnected so as to not load the 'unmodifed' signal with unwanted resistance, etc. For that, you don't use the second pole to disconnect the circuit, you use the two poles in tandem, one each to control the input and output jacks.

(Forgive me my lack of a diagram, I'm on another computer at the moment. If no one has posted anything in a day or two, I'll whip one up for you.)

In a true bypass scenario, Pole #1 has the center (common) terminal coming from the input jack's Tip terminal. The upper throw goes to the circuit, and the lower throw goes to the corresponding terminal on Pole #2. Pole #2's center (common) terminal goes to the output jack's Tip terminal. The upper throw comes from the output of the circuit, and the lower throw comes from the corresponding terminal of the Pole #1. In brief, the two poles will either route the signal through the effect, or completely around it.

Switching battery power off and on will require that 3rd pole you've been talking about. Also, it's a good idea to place those connections in series with the input jack's power control terminal (the Ring terminal). You may experience a slight pop each time the switch is pushed - a small cap across the battery terminals should take care of that.

HTH


sumgai

[vonFrenchie]

Im not quite sure if i catch your drift

[sumgai]

vF,

Ah yes, the vagaries of textual descriptions when no cocktail napkin is near to hand.

The essence is, one pole per jack. The input jack has Pole #1, which controls where the signal will go - the circuit, or through a straight wire over to Pole #2.

The output jack has Pole #2, and it receives the signal from either the circuit, or from the input jack, via Pole #1 and the straight wire.

In summary, when the switch is 'up', the signal goes from the input jack to Pole #1, through the circuit, out to Pole #2, and over to the output jack.

When the switch is 'down' the signal goes from the input jack to Pole #1, through the wire that connects the two poles, and then to the output jack.

Note that in that last scenario, the circuit is not connected to either the input or output jacks in any way - it is totally cut off, thus it can't degrade the naked signal. That's a true bypass.

Making the battery work when the switch is up is an exercise best left to the student. ;D

HTH


sumgai

p.s. No, I'm not back on my machine yet..... should be back up and running on Friday night, Lowerd willing and the wife don't find out!

[sumgai]

vF,

Ah, back a bit earlier than expected, I'm flying low! ;D

Here's a diagram of what I've been trying to say:




Hope that helps!


sumgai

[vonFrenchie]

If I'm correct, (I think I am) thats how its wired.

I only modified their "True Bypass" wiring with third pole for the battery switching.

This is the original

[sumgai]

vF,

It took me several moments of cogitation, but I finally doped out what was happening with Castledine's diagram. It's obvoius now that what he did was to build on the previous SPDT switch, instead of rewiring the thing properly.

My diagram is considered the correct way to do things, mainly from the standpoint of total isolation. What Casteldine did, more or less, add a wire that runs the main circuit's input wire to ground. No benefit in that, so why bother? Particularly in light of the power being switched off (per your addition), there's really no benefit to doing that.

IMHO,he shouldn't have underestimated the ability of his readers to understand why the wires were being moved to different terminals, when installing the new switch. At least, that's my take on it.

Use whichever diagram suits you, either will work. But in the future, if a tech opens up the pedal and sees Castledine's wiring on the switch, he'll scratch his head like I did, and wonder what kind of glue the builder was sniffing that day! ;D



sumgai

[vonFrenchie]

I was confused at first too. But the confusion of his switch was not as big as the confusion of Vox's set up on the circuit board. I cant figure out which wire does what! I know that your diagram is the right way.

I was going to wire the input and output jacks to the center lugs. Then the input and output of the circuit to the corresponding outer lugs then on the opposite side just wire the other two lugs together but.... I cant figure this circuit out.

If someone would help me out with this it would be greatly appreciated.

This is what I have so far. The wires coming from the circuitboard are
Brown: unknown
Green: Input
Yellow: Output?
Blue: Output?
White: Battery on when plugged in
Black: Battery (-)
Red: Battery (+)
Purple: Ground

[sumgai]

vF,

The control pot is wired "backwards" if you're thinking like a volume pot, but it's normal for that particular wah-wah design.

Without seeing the original wiring schema, I'm forced to make some assumptions, but as it looks, the cut brown wire is the same color as the brown wire coming from the input jack. That tells me that the original purpose of the green wire was to simply route the input to the output, via the original footswitch. (Which of course left the circuit connected to the signal line, thus loading it down.)

From that, I get the feeling that either the green or the brown wire will serve as the input to the circuit, but I could be wrong, so why not play it safe and do what Castledine did - cut the brown wire anyway, and use the green for the input from your new switch.

I still advocate that you leave all of the other PCB connections alone, and instead you place your '3rd pole' in series with the power lug on the input jack - that would be the really faint yellow wire. Should be safer than guessing at what the other wires do, right?

Good luck!


sumgai

[vonFrenchie]

I agree... if it isnt broken dont fix it. The only things I want to change are the input, output and battery. So that means....

The green wire is on the same pole as the input
The blue wire is on the same pole as the output
The third pole is the battery.

[momo]

Whoa, guys, you lost me early in the thread !, So I did the castledine mod and so changed the spdt to dpdt, wired as the diagram, so bypass works fine, but if i engage the circuit, I get nothing. So im thinking about this...from sumgai


IMHO,he shouldn't have underestimated the ability of his readers to understand why the wires were being moved to different terminals, when installing the new switch. At least, that's my take on it.

So I have a hard time seeing the connections on the input jack, they are as it was before the mod ie: brown wire is connected to tip, white to ring, and purple to sleeve ground. Do I have to modify this also? like i said, bypass is fine, but i get no output from circuit,just faint noise and pedal does not wha. Now if this wiring is correct, then ill post the actual circuit mod. I only changed 3 resistors and the stock inductor. Im pretty good at soldering, so there are definetly no cold soldiers, and there is continuity and the inductor, I actually put the stock one back to test and I get the same output problem when circuit engaged.
cheers

[sumgai]

momo,

My first inclination is to ask you 'did you do all the mods at one time?' Doing so leads to head-scratching, sort of like you're doing right now.

If you do several things that are closely related, then you have a fair chance of finding the culprit quickly when the job fails. But you've not only changed several component values, you've also done the bypass mod - now you don't know which is at fault, do you?

Best troubleshooting method I can think of (read; the least amount of work). is to short the switch. You want to restore the orginal wiring of Input tip (brown) to circuit board in, and circuit board out (blue) to Output tip. If the circuit now works, then you botched the bypass mod...... if it still doesn't work, then you 'miscalculated' your ability to replace components on the board, be it soldering or some other ailment.

One of those two problems seems imminent to me..... unless you're using a dead battery!

HTH



sumgai

[momo]

Thanks again, im gonna try that tommorow, I slept 2 hours last night so ill try that after a couple of coffees tomorrow morning...
thanks!

[momo]

AHA, so I got it workin... ;D, the thing is the wiring diagram from castledine is wrong, I did this Corrected Bypass Wiring Diagram
and that works fine, so the actual mods were done right but the switch wiring was off.Im not shure if you mentioned that, but its particular that the castledine diagram is still today referenced on alot of websites... ::)So how many people went wrong on this I don't know, but I learned something today, When I did the setup, I did not try to make my own logic of this, I just followed the diagram without thinking!

So anyway, now the problem I have is that the replacement DPDT switch is longer than the original and I can't wha full treble without activating the switch. Its a Carlings patent # 4440991 2A 250 V.A.C.
Are there different sizes that Im not aware of? Its at the shortest position possible and still its too long, also Im disapointed about the fake metal feel it has, it switches to easily(whimpy snap and not heavy metal feel like the original 3 pole switch). So does anybody have a link maybe on ebay that sells quality ones that would fit?
Cheers

[vonFrenchie]

www.generalguitargadgets.com/diagrams/wah_847_lo_tb.gif
(its a copy-written image)
That looks like true bypass to me

About the switch. Have you tried throwing a nut on the opposite side of the wah case. You can then move it up so that less of the switch is exposed.

[momo]

Yes I have moved the nut, its not the right dpdt, and thats the diagram i used for the true bypass.

[sumgai]

momo,

Good find, and I'm sure other interested readers will appreciate your 'field research'.

+1 for you!


sumgai

p.s. I fixed the link in your original post.

[momo]

sumgai said:

momo,

Good find, and I'm sure other interested readers will appreciate your 'field research'.

+1 for you!


sumgai

p.s. I fixed the link in your original post.

Does that mean that I get an extra star on my profile..!

[sumgai]

momo said:

........
Does that mean that I get an extra star on my profile..!

No, it's the number of Karma points. Stars denote how many times you've posted. You've got two more to go for the next level.


sumgai