King of Tone - PCB design problem?

norim_13 · July 20, 2012, 11:30:57 AM

Hi!

After building few DIY pedals with PCB bought from others, I decided I should try to make my own designs and start etching.

As King of Tone was in the list of my favourite pedals, and I happened to have the schematic, I decided this would be my first PCB (now I regret this decision... I should have tried something easier...)

I designed the board, etched it, bought the components, assembled everything and... the pedal just hums...
I checked some points of the pcb with my multimeter (only conductivity, and some spots I know that are supposed to "have" 9v), and everything seems fine. About the components, I don't know what to test... The IC (NJM4580) is probably fried (I mounted it backwards at the begining), but I've already tried with a similar one (RC4558) that has the same pinout, and still no sound.
After all this, I think the problem must be in my design, so I'm asking for help about this. Is there anyone who can tell me what's wrong here:
(sorry for the huge image, but I think it's better to check the circuit)

In the PCB are not shown the DIP switches and trim pots because DIY Layout Creator doesn't support them... I think you know where they are supposed to be

The schematics I used are from Madbean (Aristocrat project). Can I post the schematics here? (I read something about some schematics not being allowed to be posted...)

At the moment I'm testing the circuit with only in and out jacks, and all ground wires connected in a breadboard (no 3PDT, no LEDs, no battery snap, and only the first stage of the circuit (Side 1) and jacks).

Thanks for reading all this. I will appreciate any help.
João Norim

slacker · July 20, 2012, 01:23:10 PM

I haven't checked it all, but there are some mistakes that will stop it working.

D7 is the wrong way round, if you are getting 9 volts after this then you must have built it the correct way round.
You are missing R12 and C11 (your R12 is in the R13 position) this means your VB voltage is wrong, this will stop it working
R2 is connected wrong, it should go from pin 3 of IC1 to the VB trace, you have it the wrong side of C1.

The schematic is here for anyone else http://www.madbeanpedals.com/projects/Aristocrat/index.html

norim_13 · July 20, 2012, 01:34:00 PM

Tyvm.
I'll check all of that tonight.
About D7, I got that wrong, but as I checked there was a problem there, I bypassed it to have 9v at the IC.

Thanks again. iI'll leave here some news later

Regards

norim_13 · July 20, 2012, 05:11:28 PM

Hi!

Fortunately, I have sound coming out of the pedal! Thank you very much slacker, I'm closer to get this done.

Although I have sound, it's not perfect, in fact it's awful... It's highly distorted, and seems like my fuzz factory with max compression and stab...
I don't have C8 (1uF polyester capacitor) connected. Can it be the problem?

Best regards
João Norim

norim_13 · July 20, 2012, 07:13:08 PM

Btw, slacker already gave the link, but here are schematics:

<Sorry, was asked to remove this link.>

bean · July 20, 2012, 07:54:54 PM

Quote from: norim_13 on July 20, 2012, 05:11:28 PM
Hi!

Fortunately, I have sound coming out of the pedal! Thank you very much slacker, I'm closer to get this done.

Although I have sound, it's not perfect, in fact it's awful... It's highly distorted, and seems like my fuzz factory with max compression and stab...
I don't have C8 (1uF polyester capacitor) connected. Can it be the problem?

Best regards
João Norim

Check to make sure you are getting 4.5v on the VB supply. Sounds like you ICs are not biasing correctly. C8 has nothing to do with that.

In fact, leave C8 and C19 off altogether and just use 1uF film caps for C9 and C20. Also, 47n for C1 and C12 is a big improvement, IMO.

norim_13 · July 20, 2012, 08:23:39 PM

I think the problem must be there...
I measured that, and I think I got about 9.4v from the PSA, and ~9.2v in VB... I have to recheck that. It should be a problem in R12, right?

Thanks
João Norim

bean · July 20, 2012, 08:40:23 PM

You do not have a second 47k (R13) on PCB1 to create the voltage divider which makes VB. That's the problem.

norim_13 · July 20, 2012, 08:57:11 PM

I added R13 after slacker told me it was missing... But I'll recheck that. The problem must be somewhere in VB circuit...

norim_13 · July 21, 2012, 05:55:09 AM

I checked, and I have 9.4v from DC, and 5.2v in VB.

Shouldn't it work like this?

norim_13 · July 22, 2012, 07:46:10 PM

As my hope for this PCB is gone, I've already started working in a new one.
By now I already have 1 channel completed (only missing the VB section, and pin 8 connection to 9v).
Can somebody check if everything's ok here:

Thanks and best regards
João Norim

slacker · July 23, 2012, 01:30:39 PM

That looks almost correct to me.
You have a connection from pin 7 of the opamp to VB, that shouldn't be there.
I think the switch is wrong, it should connect D2 and D3 to pin 7 of the opamp. It should connect D5 and D6 to VB, it looks like you have it connecting both sets of diodes to pin 7.

norim_13 · July 23, 2012, 05:14:47 PM

You're right. I connected the top left switch pin to both, pin 7 of IC and VB. It should only go to VB.
Later I'll upload the complete new layout.

Regards
João Norim

norim_13 · July 23, 2012, 07:30:05 PM

Just finished the new layout. Just need somebody to check this one, and I'll give KOT another chance

Here it is:

Thanks and best regards
João Norim

EDIT: Again, DIP switches and Trim pots are not in the layout because are not available in DIY Layout Creator.

norim_13 · July 25, 2012, 12:51:46 PM

I tried a new layout: 3PDTs, Volume and Tone Pots and Jacks onboard. The only components which will have to be wired are gain pots and DC Jack.
(in the layout is missing a jumper between 9v and one of the ICs pin 8, and also Input jack conection to ground ).

Could you please verify this? I'am ready to etch, but this time I prefer that someone checks it before to avoid mistakes as in the last time...

Here is the layout:

GodSaveMetal · July 29, 2012, 01:11:04 PM

Quote from: norim_13 on July 25, 2012, 12:51:46 PM
I tried a new layout: 3PDTs, Volume and Tone Pots and Jacks onboard. The only components which will have to be wired are gain pots and DC Jack.
(in the layout is missing a jumper between 9v and one of the ICs pin 8, and also Input jack conection to ground ).

Could you please verify this? I'am ready to etch, but this time I prefer that someone checks it before to avoid mistakes as in the last time...

Here is the layout:

OHHHH! mine I have loking for these!!! is it cheked??? thanks man; I´ve TUNED on these!!

Isakajr · August 07, 2012, 03:48:54 PM

Hi Guys, I`m willing to try this. Can you supply the PCB for transfer?

norim_13 · August 08, 2012, 06:22:14 PM

Hi!
I will test the layout as soon as possible. Just waiting for some parts to arrive...
If it works fine, I'll send for anyone who's interested

Best regards
João Norim

Isakajr · August 08, 2012, 07:32:33 PM

Cool João. I`m waiting some of those odd diodes too..

News:

King of Tone - PCB design problem?