Issues building my landtone klon clone. No sound on or off, led works with 9v co

[jdoughty]

So I just wrapped up my first pcb build. First sign something was wrong was the led didn't turn on when I put it on battery power. I plugged in the 9v cord and the light came on. However, when I plugged in my guitar and amp, I got no sound (except static), regardless of if the effect was on or off.

I have rewired my switch a couple times and redid the battery wires just in case, but no avail.

I mostly need ideas. Not sure the best ways to proceed.

Images are the kit as it is atm, and the last is the image of the completed kit  that landtone has on their kit pages

[antonis]

Hi and Welcome..!! 

Can't find any building doc at the time but your 3PDT switch wiring makes no sense..

[willienillie]

but your 3PDT switch wiring makes no sense..

It seems to match the example picture.  It's used as a DPDT, like the (buffered bypass) originals.

I see some solder joints that could use some touchup.

Socketing the germanium clipping diodes was a good idea, but socketing the silicon power diodes is overkill, and sockets can have flakey contacts sometimes.  Probably not your problem though.

Can you measure and post the DC voltages for each IC pin (relative to ground)?

Edit:  I just noticed this:

I have rewired my switch a couple times

Cheesy as it is, those switches don't tolerate soldering heat very well.  You can ruin the switch with just the first solder if you're not careful and quick.  Multiple times soldering is even worse.  If you have a meter with a continuity test, you can check if it's still working correctly.

[jdoughty]

I've got some spare switches so I'll see if that's the issue. I'll start there and then report voltages. Will be a few hours before I have the chance, but I'll try to do it tonight.

[Marcos - Munky]

First of all, welcome.

Leave the switch alone for now, it may still be good and each time you apply heat on it (to desolder this one, for example), you have the chance on damaging it. I mean, just do the continuity tests. The most important things now are the continuity tests on the switch and IC voltages.

[jdoughty]

Ti1072 in middle
1.043
1.273
1.29
-.57
1.289
1.068
1.093
1.33

Ti1072 between the yellow caps
1.414
1.414
1.13
0
1.273
1.292
1.475
2.05

The 7660
2.05
.5
0
-.446
-.468
.998
1.23
2.04

Did the same on the switch and got 0s. This was after a new switch. The new switch behaves as the old one did (led light comes on, but that's it) so I'll be saving the old one for later use.

[bluebunny]

Welcome.  You have almost no power getting to those opamps.  What's the voltage where the power enters the board?

[jdoughty]

I was a moron and left it on all night and had to replace the battery... But now it's looking like it was dying before.

Wee bit different results

New values:
Middle:
-4.15
-4.1
-4.05
7.7
-4
-4
-4
0

Between yellow caps
-4
-4
-2.75
0
-4
-4
-4
-8

7660
-8
-4
+0
+3.6
7.5
-3.5
-5.85
-8

[jdoughty]

Ok, so I figured out my problem after coming back with a month's experience with other perf board pedals. Using and audio probe I was able to determine the output jack had two wires crossed!

I now have a working pedal with working gain and level control! However, the tone doesn't work, and it appears to be stuck in a warm setting. Any ideas how I should go about troubleshooting a tone control? I checked both sides of the pot with my probe and there is signal, so I'm curious if I need to look at it a different way.

[jdoughty]

Ok, so checking the schematic I'm still a bit confused.



So both sides of the tone pot appear to be a single part. So there's no issue getting signal through there. Where I get questions is the output of the tone pot appears to be a decent volume sound, but on the other end of C14 (3.9n) it is weak as it goes into pin 6 and the 100k resistor. Is that expected or do I potentially have a weak solder joint?

[PRR]

The whole thing is a treble-only Baxandall. Pin 6 is a "Virtual Earth". The signal here should be "zero". (Not dead zero, but not useful.)


Does your display need a new lightbulb?

[jdoughty]

Does your display need a new lightbulb?

I know, I thought the same thing 🤣

Ok, so the weakness of the signal isn't a clue to what's up then. How can I troubleshoot otherwise?

[PRR]

I would take it in bright light with a good magnifier and examine the joints.

[DIY Bass]

If your new IC voltages posted above are accurate, then there is something significantly wrong with the power supply.

[jdoughty]

Ok, I'll look into that tonight then. It wouldn't surprise me since the battery still doesn't work. I'll see if something is off

[jdoughty]

Latest values:
7660:
1:9
2:4.5
3:0
4:4.5
5:8:5
6:4.5
7:7
8:9

Middle 72:
All 4.5 except pin 4 was 8.5 and pin 8 was 16 which seems high

Yellow caps 72
3:3
4:0
8:9
1,2,5,6,7:4.5

I did fix some sauders that light show. Through, but there is no impact on the audio

[jdoughty]

Btw, how do you guys get the expected voltages?

[jdoughty]

New images in case they can help:

[DIY Bass]

There is a good analysis of the circuit here: https://www.electrosmash.com/klon-centaur-analysis

If you look through, the first op amp (TL072) is powered by +9V and 0V.  The second is powered at +18V and -9V.  The other pins are biased to around 4.5V.  If pin 4 of the middle TL072 could have been -8.5V rather than +8.5V then you are in the ballpark for those ICs.  Pin 3 of one of the TL072s at 3V may be a little off.

[jdoughty]

This is starting to make sense now... Ok, I'll check the solders around pin 3 first opportunity I get. I'd bet I missed the negative on the 8.5.