Author Topic: DPDT Switch, help please.  (Read 11554 times)

somasix

DPDT Switch, help please.
« on: January 30, 2006, 10:50:35 AM »
So, I finally secured a DPDT switch and was in the process of boxing my NPN circuit into a small enclosure.  When I wired up the DPDT switch, it worked in the effect:on position, but went silent in the bypass position.  Anybody have any idea why this might be?  Can I have this switch upside down?  I only got that DPDT because I thought it might be easier.  Learn me to try and make it easy on myself.

Thanks.

Jayco

Re: DPDT Switch, help please.
« Reply #1 on: January 30, 2006, 12:01:03 PM »
A couple things come to mind...

with the bypass side of the switch, did you tie the two outer blades together?

1   2
3   4
5   6

IE - pin 3 is the input of your guitar, pin 4 is the output of the amp, pin 1 is the input to the effect board, pin 2 is the output from the effect board and then pins 5 and 6 should be connected together for the true bypass.

Also, if you are unsure about the positioning of the DPDT (which blades do what), get out your good old multimeter and set it to check continuity.  You can then see which blades connect to what in the various positions.  It will help you understand how its oriented.

Jim

somasix

Re: DPDT Switch, help please.
« Reply #2 on: January 30, 2006, 02:40:27 PM »
Thanks for the reply.  Unfortunately, I bought this Harbor Freight digital multimeter.  I can seem to get the dang thing to do anything except sit there looking yellow and cheap.  The directions are no help either.

The DPDT switch I got is from Small Bear.  One side is marked with a large L.  The other reads: alpha 1 2 3.  Each number corresponds to a blade, but none of them correspont with the blade values in the last topic reply.  I'm sure it would make more sense if I had more experience, or a working multimeter.

Jayco

Re: DPDT Switch, help please.
« Reply #3 on: January 30, 2006, 02:48:17 PM »
yes, my blade values were a "for instance"... I'm not sure how Steve's are labelled in comparison.

You definitely want to either get a different multimeter or figure out how yours works, as it will save you many times over :)

In a DPDT switch, there are three rows of 2...  the MIDDLE row is what I referred to as 3 and 4 and then the other two rows are 1 and 2 and 5 and 6.

So just treat it like this:

to input of effect ---> X   X <--- from output of effect
input from guitar---> X   X  <--- to amplifier
bridge these two---> X   X
                                |__|

Jim


somasix

Re: DPDT Switch, help please.
« Reply #4 on: January 30, 2006, 04:28:40 PM »
Jim, that was a note perfect description.  That did 'er.  Sounds great, again...  Now I gotta figure out how tl get all this stuff in the little enclosure I bought.  Wire spaghetti.

It's funny how many mistakes you can make when your'e paying absolute attention. 

Thanks.   

Jayco

Re: DPDT Switch, help please.
« Reply #5 on: January 30, 2006, 04:31:56 PM »
No problem... glad to help.

I know the feeling... I built the NPN boost a while back and bought a 1590B box to put it in...  I finally got it all to fit, but it wasn't pretty :)

Jim

somasix

Re: DPDT Switch, help please.
« Reply #6 on: January 31, 2006, 09:14:30 AM »
Oh yeah, I bought a 1590B.  Did a good job drilling it too.  It's not gonna fit in there.  Tried that already.  Effects, like sex, don't work when you stuff 'em.  I'll save that for the next one, or the one after that. I might have to accept that I'm not immediately gonna be a "small build" guy.

Instead, I found this big old military intercom box.  It had a five way switch (actually four with a momentary switch) and a potentiometer and two 1/4 jacks at the back.  Perfect for a pedal.  I pulled out the switch and pot, drilled the one of the holes a little wider for my DPDT and put the whole shebang in there.  I'll post pictures after I saw down this randy looking rat shack 5K pot and put the original knob back on.  It looks sweet.  I actually wish I had more of these boxes. 


somasix

Re: DPDT Switch, help please.
« Reply #7 on: January 31, 2006, 11:44:12 AM »
All right, I'm not out of the woods yet.  Finally got to spend some time actually playing through the circuit and...  either the booster is being bypassed completely, or the unaffected signal. 

Is the knob supposed to control gain, or volume completely.  When I roll off the knob, the signal drops to nothing (as in, no sound).  This happens in either state of the DPDT switch.

I don't notice any gain boost right now (this circuit has produced one though, so I know it can do it).  Is it possible that the boost: off-state can be affected by the pot? 

Is this a pot problem, a switch problem, or both.  I rebuilt parts of this circuit after my ham fisted attempt at stuffing the dang thing into the small box.  Curse my impatience.  Is it possible I wired up the pot wrong?

Thanks.

Jason

Jayco

Re: DPDT Switch, help please.
« Reply #8 on: January 31, 2006, 11:58:30 AM »
Jason,

With the DPDT switch wired as I told you about, the entire audio circuit should be bypassed in one switch position.

In the other position (assuming your built the NPN Boost project), the pot controls boost, but does NOT completely cut signal even at its lowest point (unless for some reason you used a different taper/value pot other than 5K... then I'm not sure what it would do).

You said with the DPDT not being used, that you had it working?

Jim

somasix

Re: DPDT Switch, help please.
« Reply #9 on: January 31, 2006, 12:15:02 PM »
Yeah, when it was just a bunch of jacks, the pot, and wires sticking off the circuit board, it worked.  Then I added the DPDT and tried to shove it into the small box (I'd maintained my cool up 'til then).  Once it was in the box, no sound. 

So, After a week, I got some replacement parts, pulled all the wires off, and the 47uF electrolytic cap on the 5K pot, and redid them.  After a few grounding problems, I got a signal. 

I wired it up like the diagram you posted (great diagram by the way).  I thought it worked.  Here are a couple of particulars I can mention that might help.

1.  My input jack seems to be a weak link.  When I plugged it in this morning, it didn't work.  Wiggled the input lead with my finger.  Static, noise, then sound (but this was when I noticed 'no effect'.

2.  I redid the wiring and 47uF on my pot.  Is it possible I did these backward, or wrong?  Might this contribute to my volume drop out?

I think now is a good time to take lunch and come back to it.

Jayco

Re: DPDT Switch, help please.
« Reply #10 on: January 31, 2006, 12:23:13 PM »
Given that everything shares a connection to ground, I would wonder if maybe the pot is indeed wired backwards.

The cap on the pot is polarized, so yes, you want to make sure that it is in the correct way... I don't have the schematic in front of me to look but you need to make sure that the - side of the cap is connected to the proper place on the pot.

Double check the pot and cap from the schematic and let me know if its still giving you issues... I'll take a look at the schematic.

(I'm heading for lunch too!)

Jim

tennisdude

Re: DPDT Switch, help please.
« Reply #11 on: January 31, 2006, 06:47:21 PM »
hi, I just read through this, maybe some pics would help? do you have a digital camera?

somasix

Re: DPDT Switch, help please.
« Reply #12 on: February 01, 2006, 09:20:34 AM »
My girlfriend has one.  I'll have to wait until tonight to post some.  I haven't had an opportunity to go back and look at my work.  Life got in the way for a moment.  More later.

somasix

Re: DPDT Switch, help please. (pics)
« Reply #13 on: March 27, 2006, 12:16:45 PM »
Sorry I've been offline for so long.  I work long freelance hours (when I'm working) and this is the first downtime I've gotten in a long, long time.  Anyway, here are some images of the board, the DPDT, and the pot.

I finally got a working multimeter, and while I'm not totally sure I understand how it works yet, the reading I got from the spot where the battery attaches to the output jack was 5.25 on the 20 DVC setting.

To reiterate my problem, the potentiometer controls overall volume (all the way up, all the way off) not boost, and the DPDT seems to have no affect at all.











« Last Edit: March 27, 2006, 12:21:41 PM by somasix »

aron

Re: DPDT Switch, help please.
« Reply #14 on: March 27, 2006, 09:29:43 PM »
That switch looks to be in bad shape. The rest of the board is pretty good. Check out the pot and make sure none of the wires are shorting out. Measure the voltage at the 3 transistor legs and at the positive terminal of the battery.

Aron

somasix

Re: DPDT Switch, help please.
« Reply #15 on: March 28, 2006, 11:48:47 AM »
All right, I'm about to replace this switch.  Meanwhile, using my DMM set to 20DCV, the readings I got for the transistor legs were as follows:

C = .12
B = 1.60
E = 2.22

How do you use the multimeter to check continuity?  I can't say I totally understood the link in Using Multimeter.  Thanks.

Jason

somasix

Re: DPDT Switch, help please.
« Reply #16 on: March 28, 2006, 01:24:20 PM »
So, I replaced the switch and resoldered a loose connection on the pot.  Plugged in the booster while it was attached to the top of the case and it worked fine.  Subtle and lively boost on the guitar.  Attached the bottom of the case and that was the end of the booster.  Pedal returned to its pre-debugging state as a off guitar volume knob.  Took the top (basically all the knobs, wiring, and circuit) and once again, booster works again.  It there a chance that the battery is shorting out the DPDT or the enclosure bottom is cutting the effect?  The enclosure is made of aluminum.  Should I put a piece of foam in there like MXR does?


woulfer

Re: DPDT Switch, help please.
« Reply #17 on: March 29, 2006, 10:07:12 AM »
I would guess either something is shorting out to the case when putting the lid on, or there is a loose connection that is coming free when everything is stuffed in the case.

somasix

Re: DPDT Switch, help please.
« Reply #18 on: March 29, 2006, 12:24:41 PM »
Examining the numbers I got from my DMM against some of the others found on the forum, I'm a bit concerned about them.  Do those numbers seem right?  Could there be more going on than just my case shorting out the circuit. 

I'm having my doubts about the state of my circuit at this point.  Although the signal seems to make its way through the circuit and the knob has an affect on the overall tone (from clean to murky), I'm no longer noticing any boost in or out of the case.  Any perspective on the constantly shifting state of this circuit would be much appreciated.  I just don't understand what I'm supposed to do to get a once working circuit to work inside it's case.

woulfer

Re: DPDT Switch, help please.
« Reply #19 on: March 29, 2006, 01:10:29 PM »
I would get your pedal out to where it is working, and then take the voltage readings. It still seems like something is shorting out to me.