Help with Effects Layouts Break Action Debugging

[ddavis20341]

Hey all, I have an Effects Layouts Break Action (a JHS Double Barrel-style TS and Bluesbreaker in one pedal) that I need some help debugging. It's a 2 channel pedal, independent bypass for each channel.

The Morning Glory side of the pedal works fine, bypass works fine, both LEDs light up and I'm getting voltage into the circuit, but my TS side isn't passing signal. I did a little bit of testing with an audio probe and I lose signal after it comes into pin 3 on the TL074 (link to schem posted below). I get audio into pin 3, but then I don't get any audio out of pin 2 or pin 1 after that

I did mess up the clipping toggle on the TS-side when I was building it and accidentally put in a momentary switch that I had to swap out, so I'm wondering if that might have something to do with it or inadvertently burned something out while doing that. Any help would be greatly appreciated! I'm pretty stuck.

Schem: http://effectslayouts.com/wp-content/uploads/2020/02/Break-Action_build-doc.pdf
Voltages:

TL074 (IC2)

1: 8.5V         14: 8.4V
2: 0.45V.      13: 8.4V
3: 7.8V.        12: 8.4V
4: 9.2V.        11: 0V
5: 3.9V.        10: 3.9V
6: 7.8V.         9: 7.8V
7: 7.8V.         8: 7.8V

2n5089 (Q1) <- Schematic has 2n5088 here, but parts list calls for 2n5089

C: 9.2V
B: 7.05v
E: 6.76V

Pics: https://imgur.com/a/36bUec6


Full Debug Checklist:
1.) Break Action not passing signal on TS-side
2.) Effects Layouts Break Action (JHS Double Barrel-style pedal)
3.) http://effectslayouts.com/product/break-action/ , http://effectslayouts.com/wp-content/uploads/2020/02/Break-Action_build-doc.pdf
4 and 5.) Stock Circuit
6.) Negative Ground

[Kevin Mitchell]

Check the connection of the CLIP2 switch. That bottom lug looks suspect. Make sure it has continuity with all 3 connections on the PCB.

[iainpunk]

hey, welcome to the forum,

this looks like a perfect job for the Audio probe.

its a simple device to track where audio is and, more importantly, where its not

the voltages on the TL074 look really odd as well, what voltage does VR read?

cheers, Iain

[ddavis20341]

Thanks for the replies and thanks for the welcome, Iain.

I'm a newbie at reading schematics and the more technical parts of building, so bear with me. I did some continuity readings - bottom lug doesn't give me continuity with anything in any position (including the LEDs it's supposed to connect to). Top lug only give continuity to D2 and D3, but not D1. It also lights up the bottom LEDs when I check continuity with either of the leftmost LED pads. Middle lug doesn't have continuity with R7.

R6 does have continuity with the Drive leg 3, C3 has continuity with R7, and Drive leg 1 has continuity with C3 and R7.

So, if I'm assuming I fried those pads and need to use jumpers, I would jumper the middle lug of Clip2 to R7 and jumper the bottom lug to D4/5? I would also love a quick rundown on how to read clipping diode and switch diagrams like that - I still don't understand them after trying to do some reading on my own.

@iainpunk, what is a good place to grab VR from? Just measure at any of the points where it's going into the circuit as +VR?

[iainpunk]

@iainpunk, what is a good place to grab VR from? Just measure at any of the points where it's going into the circuit as +VR?

its the voltage in between R32 and R33

cheers, Iain

[Ripthorn]

Usually, if you have signal going into an opamp and nothing coming out, it's either a Vcc problem or a Vref problem. I was dealing with one just last night where something touching my board was actually shorting my Vref connection. Maddening I say!

[iainpunk]

i want to re-state that the Audio Probe is a must have, when de-bugging pedals!!!!!!!!!!

Usually, if you have signal going into an opamp and nothing coming out, it's either a Vcc problem or a Vref problem. I was dealing with one just last night where something touching my board was actually shorting my Vref connection. Maddening I say!

i know the frustration all to well, i had a breadboard with a piece of wire strand shorting out a track on a place i couldn't see because the IC was covering it up, that cost me a full day in debugging. (CA3130, it was between pin 5 and 6, the output and the non-inv side of the offset null, it kept oscillating)

cheers

[ddavis20341]

I'm getting 7.82v as VR

[iainpunk]

I'm getting 7.82v as VR

that should be a lower voltage, near 4,5v,
check the voltage on the leg on the other side of the resistor R33? the leg specifically, not the solder or trace, since those could be the problem.

cheers, Iain

[ddavis20341]

I'm getting 7.72v on the leg of R33 (and R32) closest to the middle of the board, which connects R33, R32, and the positive leg of C26. On the other leg, I'm getting 0v at the moment.

[antonis]

I'm getting 7.72v on the leg of R33 (and R32) closest to the middle of the board, which connects R33, R32, and the positive leg of C26. On the other leg, I'm getting 0v at the moment.

If so, check R32 value..

Also, what is the voltage reading on R34/R35/C27 junction..??

[ddavis20341]

Thanks again for all the help yall. Antonis, great thought. I double-checked the values a couple of days ago using the color codes, and actually decided to replace them with fresh 100k resistors this morning just to be safe (and also make sure I didn't have any solder bridges around them or anything).

I'm getting 4.5v on the R34/35/C27 junction. I'm also getting the full 9.2v on the side of R32 that connects to +9V. Super confused right now what the problem could be.

[antonis]

Good news both for +9V and V_REF..!! 

Lets take now some fresh voltage measurements..

[ddavis20341]

Full round of fresh votlages:

+9V: 9.45v
1N5817: 9.45v on +9v side, drop to 9.18v
R32 : 9.18v on +9v side, 7.78v on side connecting to R33
R33: 7.78v on side connecting to R32, 0v on ground side
C26: 7.78v on + leg, 0v on - leg
R34: 9.18v on +9v side, 4.59v on side connecting to R35
R35: 4.59v on side connecting to R34, 0v on ground side

TL074 (same as 1st measurements)
1 - 8.5v,    14 - 8.4v
2 - 0.5v,    13 - 8.4v
3 - 7.8v,    12 - 8.4v
4 - 9.18v,  11 - 0v
5 - 3.88v,  10 - 3.8v
6 - 7.8v,    9 - 7.8v
7 - 7.8v,    8 - 7.8v

I also noticed that Clip2 has no voltage across it, while Clip1 has 4.5v on every lug.

[ElectricDruid]

R32/R33/C26 still aren't right. Those resistors are equal, so the voltage in the middle should be half the supply voltage.

You mentioned that you've got 4.5V on the R34/R35/C27 junction. The R32/R33/C26 is exactly the same and should give exactly the same voltage.

Double check the values of those resistors, R32 and R33. The voltage is too *high*, which rules out a short across the cap (that would give a voltage that's too low). 10K instead of 100K for R32 is easy to do, but would give over 8V. That Vr reading is the first and most important thing to fix.
If the two resistors making up the divider are ok, check the others that connect to Vr: R3,R4, R8, R12, and the pot B100K/Volume1.

The op-amp voltages are all over the shop. The first two stages (pins 5,6,7 and pins 8,9,10) are both wired as voltage followers, but they're not following the input voltage (3.8V) at all. However, until that bias is solid, I'm inclined not to worry about those too much. There's a lot of problems in the op-amp stages, and the only thing they all have in common is... that bias voltage! (given that Ground and 9V are actually ok, which seems to be the case).

It's weird though...the Vr at one end of R3 is 7.78V, and at the op-amp end (pins 5 and 10) it's 3.8V, pretty much exactly half. That implies you've got a resistance to ground, and not a dead short. That could happen if C1 had a short, or if the cap was bad, perhaps. Just some muck, a tiny strand of wire, or something could do it.


HTH,
Tom

[ddavis20341]

So I double-checked the values of R32, R33, R3, R4, R8, R12 and Volume1 (and also had someone else check them as well), and they all look to be correct. I grabbed voltages for all of those, and they all seem to be consistent with the readings from the IC:

R3: 7.78V on VR side to 3.8v on IC pin 5 side (the weird drop), R4: 7.8V on VR side to 7.8V on IC pin 3 side, R8: 7.8V on VR side to 8.4V on IC side (assuming that matches with pin 1 voltage minus the drop from R7 1k), R12: 7.8V on VR side to 7v on Q1 base side, Vol1 pot : 7.8v on leg 1.

Also tried cleaning up the board, re-flowing all of the traces for that side of the circuit, and swapping C1 for a fresh cap (and checking around it for connections), and it's still giving me the same weird readings. R1 and R2 also seem to be the correct values as well.

Is there any workaround to get a good VR into the circuit? I'm sure it's probably something small that I'm missing somewhere, but I am thoroughly out of ideas at this point, other that trying to swap out every single one of those resistors (which I already did for R32 and 33).

[ElectricDruid]

You could try pulling out anything you've got socketed, and then testing the Vr voltage again. Sometimes if there's a dead chip/tranny that's pulling something down, the voltages will be fine without those parts in, but then go wrong when you put them back.

[ddavis20341]

Wow, some true wizardry right there. So I pulled out the TL074 and took some measurements. VR without it in there? 4.38v at all of the points connected to it.

Going to order a fresh one today and see if that fixes things!

[ElectricDruid]

That would explain why the voltage followers weren't following voltage too!!

Just to check, it wasn't back to front, was it? Or the socket?

[ddavis20341]

Nope, it was in correctly (at least according to the printing on the board), and the socket was also the right way around. In another interesting development, I finally got a new TL074 in yesterday, plopped it in and.....nothing.

I haven't checked voltages yet, but suspect they would probably be the same. Could I have a solder bridge somewhere around the socket or something?