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Permalink Reply by David L. on April 25, 2015 at 7:15am

If you are unable to check continuity if you have two test wires you can check to see if the preamp is always on as described above.

The first diagram assumes that like my preamp it is always switched on so you cut the black wire from the battery, extend the two cut wires and add a switch between them.  As described earlier live output (top blob of solder) needs soldering to the 3 way switch and the left lower lug to common ground.

If this doesn't work (because it functions as it should) or if you are able to decide that it isn't switched on permanently without a jack plug inserted then the second diagram shows what to do.  The only wire you change is the cut battery - wire going from switch to the PCB and instead this part of the switch is connected to the other big blob of solder bottom right.

I picked up several belcat parts and had to hack them from the EQ module as they were missing the battery box.  For these to work the white wire had to be connected to the common ground so add another wire from this connection at the switch to the common ground as shown.

Good luck with it - when soldering to the three blobs connecting to the 1/4 inch jack socket be sure to tin the tip of the wire so you get a good connection.

Again please ask if there is anything that needs further explanation.

David

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Permalink Reply by Matteo R on April 25, 2015 at 11:50am

Ok guys,  I've got some news; I've looked on the internet to understand how to check continuity, it looks easy enough. If I understood, I have to turn the multimeter ring nut to continuity mode, it is the one that it sounds when I put the tips in contact.

The thing it's not totally clear is where I have to place the tips to check continuity; I have an idea, but I want to be sure for everything to work. Anyway, I guess tomorrow I'll try if I can figure it out.

I almost forgot: I'm curious about what The Phrygian Kid said, about the diode and the master volume (the type of diode needed and how to wire the circuit).

In the meanwhile, I thank you guys for your precious help you gave me, without you it would be impossible for me to wire this circuit. If I get rich, I'll build you a statue, I promise you. :)

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Permalink Reply by The Phrygian Kid on April 25, 2015 at 11:39pm

a multimeter is the thing to get. It will be around $10 at your local large auto-parts mall.

checking continuity with a multimeter.

your (cheap) multimeter will have two probes connected to it, marked + and - , usually red and black.  Most will have a rotary switch for the various tests it can do.   You want to test resistance, which is measured in ohms (Ω) it may have several positions in this rotary switch for resistance with different numbers, and some may be marked in other units of resistance, which are a multiple of ohms, (㏀, ㏁).   These alternate settings are ranges of resistance, for this purpose we can put it on any of them.

The result will usually be in a little pocket calculator style lcd.  At the moment it will be indicating infinite resistance (no continuity).  Most cheap units indicate this with a '1' on the screen, but your mileage may vary.  Touch the probes together and it will indicate zero (or very very close to zero) resistance (ie full continuity).  Mine will show '0'.   So its very easy, just by briefly touching the probes directly to each other, to see how your unit indicates the difference between a connection and a disconnection.    Touch the probes to two of the lugs on a switch and flip the switch.  Swap to a different two lugs.  You can quickly work out exactly how the switch works.  Try it again with a potentiometer.   In my opinion this is much better than relying on other peoples diagrams etc from the internet;  not all cheap electronic components work exactly the same as each other.  But once you know this stuff you can understand how your guitar circuits work, and in no time you'll be designing your own.

Incidentally, I'll always cut the probe bit off on the (-) side and replace it with a 40c alligator clip, so I can clamp it somewhere (usually ground on a guitar circuit, the bridge or the sleeve on the jack connector) and run tests with only the other probe, I just find em much easier to use with a clamp on one end, and you can still just poke it at things when you want to

Diodes.

there are several kinds of diodes.  Any kind at all will do for this application, even a LED that you clip out of a computer speaker or something before you throw it away.  If you go to your electronics supplier (JAYCAR here in AU) they'll (diodes, not LEDs) only be 10-15c each, so its no biggie to keep a little baggie of em in your circuitry stash.

If you try the continuity testing I outline above on a diode you might see zero continuity.  Reverse the  probes and you'll see full continuity.  WF is dead right, they're like a valve, and will only let current pass in one direction.   The end which your (+) probe is connected to when you get it indicating a connection is the 'input' side.  So in the example here, I suggested put one between the volume pot and the switch,  You'd connect that 'input' side to the volume pot, and the other to the switch.

hope that helps

 

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Permalink Reply by darryl kernaghan on April 26, 2015 at 2:51am

i held off for P K's reply as i thought he would nail it better than me,as he did,but the answer to your which diode question ,as best as i know is a shottsky 20 A/1V is around the mark,it's not overly important,but being so cheap,why not?

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Permalink Reply by Matteo R on April 26, 2015 at 3:26am

First of all, thank you guys for your help and support.

I did a few tries, and I maybe understood how it works. I'm going to explain what happens:

1) I plugged the piezo in the EQ, then the EQ to the battery/jack module; clearly, the battery is inserted.

2) I've put the first probe to black wire that comes out from the battery, while I've touched the battery blob with the second one (placed right bottom).
The multimeter sounds, that means this two points are in continuity.

3) Keeping the first probe on the negative wire, I moved the second to the alleged ground blob (as David L suggested, placed left bottom); this time I got no sound.

4) Then, I've moved the probe to positive wire from the battery, while I've placed the second one on the positive blob (on top); as before no sound.

I repeated the last two steps, but this time I inserted a jack before to try. Surprisingly, I got sound from both (obviously positive to positive and negative to negative). So, it looks the system is switched on by plugging the jack; consequently, the second diagram David posted is the right one for me. Am I right?

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Permalink Reply by David L. on April 26, 2015 at 10:08am

Hi Matteo,

The information is really helpful.  The second diagram would work but it was the plan if the first diagram didn't work.  I think this is better

The blue wire is doing the connection that the jack does.

The red wire is the live to the 3 way and the black goes to the common ground point

The green cut on the black battery wire you extend the two cut halves and insert your switch.

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Permalink Reply by Matteo R on April 26, 2015 at 11:59am

Thank you David, your diagrams look really simple! To do a better job, instead of cutting the black wire I'll probably unsolder it from both the battery and the B- lug, to replace it with two longer wires, to insert the switch; correct me if I'm wrong, but turning off the switch stands for unplug the jack, isn't it? This way, the battery will not drains.

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Permalink Reply by David L. on April 26, 2015 at 1:16pm

The blue wire does the job of the jack plug so it is permanently on once this wire is soldered in place. By cutting the black battery wire it is off until the wire is reconnected (so putting a switch here gives you on and off control).

I was thinking of what you might find easiest to do ( ie simple soldering of wires to the existing blobs and adding the switch to existing wires) and also adding the switch where I know it will definitely turn the preamp off, but if you don't like to do that it is just as simple to totally ignore the black battery wire and add the switch to the blue wire so when on it will be like a jack plug is in place and when off it will be like the jack plug is pulled out. (So long as you are happy it is off with the jack plug removed).

I would do this rather than trying to solder new longer wires to the pcb.

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Permalink Reply by Matteo R on April 27, 2015 at 1:31am

Yes you're right. Basically it's the same, but your idea it's way better.

So, let me know if I understood: when using the magnetic pickup, I don't need to turn on this new switch I'm adding, while when I use both magnetic and piezo, or just the piezo as well, I have to turn on the switch, that it's like plugging the jack to the PCB.

It seems pretty easy; this image should explain better than words.

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Permalink Reply by David L. on April 27, 2015 at 3:08am

Yes the diagram is right and you fully understand how to use it.

Good luck with the project :o)

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Permalink Reply by Matteo R on May 8, 2015 at 11:06am

Hi guys! I'm still working on my CBG; I decided to make a few changes, adding 2 strings and 2 more pickups. So, now I have a 6 strings CBG with HSS pickups (standard Strat wiring with 5-way switch) and piezo. To see how it works, I made a diagram, that it's way easier to understand than my words. I have a doubt about it: I want to add the diode as The Phrygian Kid suggested, but I'm not sure where I have to solder it and how. Could you guys explain better? What do you think of my idea?

Here's the diagram

P.S. Obviously, I'll use a common ground.

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