Tonepad Sansamp (Sin Amp) GT-2 Build - Shielding

[strungout]

Ok, so I spent a lot of money to build something I could've gotten a Behringer copy of for dirt cheap cause I wanted to. http://www.tonepad.com/getFile.asp?id=112 If it doesn't load, try again. Had some problem DLing the PDF...

Build went smoothly, of course, using a Tonepad PCB, and even the Small Bear switches weren't that much of a hassle to wire ( http://smallbear-electronics.mybigcommerce.com/dp3t-on-on-on/ ). And everything will fit in a 1590BB box! I'm happy, cause I know I'll get this thing working... once I figure out why the voltage divider isn't voltage-dividing...

Right now, It doesn't work and my IC1a's voltages led me to check Vb. I've removed both 10k res that for the voltage divider and they're both around 9.8kohms, so they work. All my 9V point show the 9.2V from my power supply. I've re-soldered all the components whose leads are connected to Vb. All seems good. This is the first time this happens to me. Never had a voltage divider not function, that is.

Any ideas? Thanks!

[disorder]

I'd start with measuring Vb to ground. See if there's a low impedance path, that 220uF cap for example? IC installed backgrounds so Vb is trying to feed low impedance output pin? You can remove the divider res to ground if it helps differentiate what's correct reading and what might not be.

[strungout]

I'd start with measuring Vb to ground. See if there's a low impedance path, that 220uF cap for example? IC installed backgrounds so Vb is trying to feed low impedance output pin? You can remove the divider res to ground if it helps differentiate what's correct reading and what might not be.

Between Ground and Vb I do get 1-10mV, it shifts a lot.

I assumed you mean "ICs backWARDS". Nope, they're oriented correctly. And so is the 5088 transistor.

I must admit I get lost when people start talking about impedance...!

[disorder]

Yes I meant backwards, didn't have my coffee yet when I replied.

Simply set your meter to Resistance and measure ohms from Vb to ground. If it's low (in the tens of ohms to hundred of ohms range) then desolder the 220uF cap. Measure again. Take one component out at a time.  While you're at it, make sure you have continuity of course from the voltage divider to various components using Vb.

[strungout]

All I get is a 1. No other readings at all, no matter where I set my ohm-meter...

EDIT: Here's a solder-side view, looks clean to me...

[strungout]

I was kinda drunk yesterday. I forgot to check the two 220uf caps. I removed them and there was my 4.5V (or so)! Must've been a bad solder joint ( I thought I had redone them...) because I put them back in and I still have my 4.5V. AND the pedal works, almost. So, thanks for that, disorder!

The MIC switch works. The MOD switch works. But even at hot wired, the Tweed and California channels are clean and very low volume. So this is my next bug to kill.


EDIT: Ahhh, I wired switch 3 backwards! Everything works. Now on to the hum!

EDIT 2: Where do I connect the shielding of a wire? Cause now with the stomp I get real hard squealing

[disorder]

Glad you got it going. I like to drink and build stuff myself.

You might have hum if the circuit isn't installed in a grounded enclosure yet, which it looks like judging by your picture. Most people will use metal input/output jacks so that connecting their ground lug to your circuit ground shields the enclosure. The other option is to get your soldering iron real hot and connect ground to the back of a pot. If you are using shielded wire for in/out you want to connect the shield to any ground, just make sure you only ground only one end of the shield - this eliminates a ground loop.

[J0K3RX]

I was kinda drunk yesterday.

That will get you every time! I have horror stories I could tell but I won't...

By the way - Sweet looking Agile Septor! 

[strungout]

@JOK3RX: Hahaha! And yeah that was a sweet Septor, an excellent guitar, I miss it sometimes; I sold it and bought me a nice Yamaha TRBX bass and I don't regret it!


About the SAGT2, I'll have to buy more shielded wire, I grabbed too big a gauge and it doesn't fit in the PCB holes... Guess I'm stuck with oscillation till I do. But keeping the LEVEL low, I can turn everything up and not get any squealing. And I was so happy it didn't oscillation at first...

This box is rad tho! I love how crunchy the palm muting is and the amount of tones I can get out of it. Maybe I'll change my mind once I shield this thing, but for now I'd say buy a new/used one or the behringer clone. Less trouble!


EDIT: Added some build pics.





Will redo the box cause honestly things aren't really straight. Gonna paint it black and try that decal sheet I ordered from Small Bear. I'll post that eventually XD.

[smarkalet1]

Interesting way you mounted those switches. 👍

Sent from my LGMS330 using Tapatalk

[strungout]

Thanks!

I saw someone do it like this. The problem with the switches is, the rocker part gets stuck against the case if the black part doesn't clear the hole...