Klon Debugging

[mikelambresi]

Hi everyone!

Hope you are all well. Firstly I just wanna thank you for all the contribution to the forum, learnt a lot from it.

I'm having problems with my Klon build. It's one of these kits from China you see on ebay.

https://www.ebay.co.uk/itm/DIY-KLONe-Overdrive-Guitar-Pedal-Boutique-Professional-Beautiful-Gold/113078640376?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D20160908110712%26meid%3D08ca4ecd65c1429f9176ba1a899baa33%26pid%3D100677%26rk%3D1%26rkt%3D14%26sd%3D123075374333%26itm%3D113078640376&_trksid=p2385738.c100677.m4598&autorefresh=true

Essentially I get a very quite guitar signal full of distortion and noise with the pedal bypassed. When engaged, I get a lot of noise, oscillation and distortion. All the knobs seem to be effective tho, even the Tone.
I made video in order to illustrate the problem:
https://www.youtube.com/watch?v=2MDXSJpiCZQ

V+ is 9.5V and I have done no mods or substituted any parts.
This is the schematic I'm referring to:
https://aionelectronics.com/wp-content/uploads/2013/11/klon-centaur-schematic.png

DEBUGGING

Following the R.G. Keen debug guide, I measured all the voltages, checked all the ground connections, checked all the cap orientation, resistors values, double checked if the IC pins were'nt shorting, etc.
Values in brackets are the correct voltages that I should be seeing according to what I read from IvIark from tagboardseffetcs.

    IC1 (TL072)                        IC2 (TL072)                IC3 (7660)               D6 (4001)         D5 (4001)        D4 (4148)

1. +9.3V (4.43)             1. +9.6V (4.6)                 1. +9.5V (8.44)         14.1 V                 11.6V                +9.5V
2. +9.3V (4.43)             2. +9.5V (4.5)                 2. +3V (4.52)            11.6 V                 9.5V                     0V
3. +1.5V (3.45)             3. +9.3V (4.5)                 3. 0V
4.+8.6V (4.43)              4. -6.3V (-8.5)                 4. -3.3V (-4.13)
5. +8.9 (4.41) .             5. +9.3V (4.5)                 5. -6.12V (-8.42)
6. +8.6V (4.43)             6. +9.5V (4.5)                 6. +3.64 (3.97)
7. +8.9 (4.41)               7. +9.4V (4.5)                 7. +4.17 (5.29)
8. +9.5V (8.87)             8. 14.5V (15.9V)              8. +9.5V (8.82)


Correct me if I'm wrong but I can see 2 problems:
1. I'm getting voltages close to V+ (9V) where I should be getting Vb (4.5V).
2. V- and V2+ seems to low, 14.5V instead of around 17V) and -6V instead of around -9V.

In order to figure out why I was not getting 4.5V I measured the voltages around the voltage divider formed by the two 27K resistors.
Both resistors are measuring 9V across their terminals, so that's one problem. The second resistor that should be connected to ground has 9v across both terminals.
I've resolder this two resistors as well as all the IC pins joints and capacitors to see if I had a bad joint, but the problem persists.

What am I missing? Is there any further tests I can do?

Sorry for the long post and let me know if I should be giving any other info.

Thank you all in advance,

Miguel

[pinkjimiphoton]

i built one of these, so i can verify the kit works <i ended up selling it>

the 9v is probably ok, as 1/2 voltage on this circuit would be 9v, not 4.5 cuz the circuit runs at 18v.

sounds to me like your bypass switching is likely the problem.  looking at the diagram you posted, it has 4 5 6 backwards. it would be
1  6
2  5
3  4

they made the build doc kinda hard to follow. but if wired as shown, whats happening is the "a" side of the switch is switching the input jack to the input of the board, but switching the output of the board to bypass instead of the jack. swap the wires on 4 and 6 and see if it works. be careful, them switches melt fairly easily.

but looking at it, the "b" side of the switch is back-asswards

[mikelambresi]

Hey pinkjimiphoton,
Thanks for answering. The wiring is fine, it's exactly like the picture form the kit and like the instructions as you can see in the pictures, I've also double checked it with a continuity test. Even with the noise I can hear that it's working as it engages the distortion successfully.
The voltages they are not right, the Klon uses in fact 9V(V+), -9 (-V), +4.5(Vb+) and 18V (V2). Check this out: https://www.electrosmash.com/klon-centaur-analysis
The problem is that the voltage divider in the power supply with the two 27K resistors in series should have +9, +4.5V and 0V, but i'm not getting ground. Hence the reason why I'm getting V+ in the places I should be getting Vb. I've tested all grounding points in the circuit and this is the only one that is not grounded but I can't figure it out why. I've resoldered that resistor, I've resolder all the IC points and all the caps in the power supply.

What am missing here? Am I shorting ground with 4.5V? Is it a capacitor that is not blocking DC? Could it be that the trace that connects R30 (27K) to ground is faulty?
Can anyone help me on this? I don't know what else can I test...

Thanks

[Slowpoke101]

Some of these China kits can be difficult to get going. The documentation is questionable at the best of times.
Anyway, you need to sort out the 4.5V problem first. Have a look at the following pictures so what I am about to say makes more sense.




The two 27K resistors make up the voltage divider for the 4.5V rail (+Vb, Vref...whatever). If you look at the circuit it is obvious as to how it's all connected. If the the 27K resistor that connects to 0V (ground) is open circuit or the ground connection is broken the 4.5V rail must go up in voltage. As you have nearly 9V on this rail you should check this out. A short circuit to the 9V rail can also cause the 4.5V rail to go up to 9V so this is another thing to keep in mind.



Pin 4 of IC1 should be 0V. IC1 forms the input buffer for the pedal. Any problem here could cause problems elsewhere and because this is a buffered bypass effect it will also cause problems when bypassed.

Let us know how you go. You will get this to work so don't get discouraged.

[mikelambresi]

Thanks Slowpoke101.

Found the problem, as I suspected it was on the 27K resistor connection to ground.
After resoldering the resistor and no change, I got some alligator clips and and touched its leg and ground and suddenly everything worked out, all voltages lined up as well.
Desoldered the resistor with desolder braid and tested continuity between the pad and ground - nothing...
I guess there is a faulty pcb trace which to be honest I suspected but found it hard to believe.