Building the Meat Sphere

[telebiker]

Hello, I have the board in hand and the majority if not all parts on the way.  I'm excited to get into this project!
Does anyone have a drill template (the one shared in box on the first page(s) of this thread will not load for me). Also anyone feel like sharing graphics they might have used on their build?
I've read the thread and have gleaned a lot of helpful info. 
Building for a bass - any revelations from recent builds, I'm all ears.

I have this file.
https://drive.google.com/file/d/10MXV805zvi-eQg-G3M1ztVRzw934D-bD/view?usp=sharing

[telebiker]

I'm testing the PCB and got pretty weird results. Looks like filter part is not working in my build. In some settings I can hear the unprocessed guitar signal, in some setting there are no sound at all. I've rolled LED/LDRs and can see LEDs are reacting to the guitar signal.

What are key parts to look at the PCB to ensure that filter is working as expected?

I've noticed that I have very distorted signal on pin1 of LM1458.

[telebiker]

I replaced the busted pots with new ones. I originally had mounted them all in the pedal as suggested, but they didn't reach the solder pads. I thought I'd be able to bend them gently and get them to reach, and they did, but when I tightened them down with the nuts they snapped.

So now I have everything wired up, but it doesn't seem to be working in filter up mode. The envelope just doesn't trigger and the low and bandpass modes turn off the output. Works fine in Down mode though. Maybe I have a bad switch. Either way I'm going to have to spend some time debugging now...

EDIT: Is this just my build and I did something wrong, or does the intensity get reversed when it goes between up/down mode? My build seems to be working right, just wasn't expecting that odd behavior from it. Also, the blend seems somewhat useless on mine, as far left is the clean signal, moving towards middle ramps clean volume to nothing (no output), then past that to the far right is the effected output.

I have exactly this behaviour with the blend pot. Far left is the clean signal, moving towards middle ramps clean volume to nothing (no output), then past that to the far right is the effected output. Didn't get what's the reason.

[idy]

You might post voltages for the ic's, especially the 1458. And read the next to last pager of this thread where "the issue" with the 1458 triggering is discussed.

[telebiker]

Voltages:

TL074
pin 01: 4.5V
pin 02: 4.5V
pin 03: 4.5V
pin 04: 9.0V
pin 05: 4.5V
pin 06: 4.5V
pin 07: 4.5V
pin 08: 4.5V
pin 09: 4.5V
pin 10: 4.5V
pin 11: 0
pin 12: 3.8V
pin 13: 4.5V
pin 14: 4.5V

LM1458N
pin 1: 2.1V
pin 2: 2.0V
pin 3: 0
pin 4: 0
pin 5: 2.1V
pin 6: 2.1V
pin 7: 2.0V
pin 8: 9.0V

Decay pot has no voltage on lugs 1 & 2 (I think that's ok).

Sensivity pot doesn't have any voltage. Also, bandwidth switch doesn't have it as well on all its lugs. Could it be broken switch? I checked and it seems to connect required pins. I can hear clean unprocessed signal on the sensivity pot lugs 1 & 2; the same on the central pad of the bandwidth switch.

On send pad also having 0V. On the send pad I can hear clean unprocessed signal.

[idy]

Your IC voltages look OK.

Although the schematic shows Sensitivity is attached to 4.5v, pin 14, and should, unless all the way down, show something on pin 3, my notes show there is a 10uf coupling cap missing from the schematic and you are therefore OK

Are you sure you have the knobs set to work? Sensitivity max, attack min, decay about 9 o'clock, resonance noon, blend noon. Switches: Bandwidth in the middle (full), sweep up (LED off until you pick) range low, filter type on bandpass. And try a booster on your guitar.

The 1458 should show a distorted signal because it is acting as a 1/2 wave rectifier, turning your signal into DC (sort of) to trigger the LED.

The page of the thread I referred to talks about adding about 2 volts to pin 3 of the 1458 to make it bias closer to its operating range. (These things don't go lower than 2v.)

[telebiker]

Thanks for the reply!

Are you sure you have the knobs set to work? Sensitivity max, attack min, decay about 9 o'clock, resonance noon, blend noon. Switches: Bandwidth in the middle (full), sweep up (LED off until you pick) range low, filter type on bandpass. And try a booster on your guitar.

With these settings I hear clean guitar signal unfortunately.

The page of the thread I referred to talks about adding about 2 volts to pin 3 of the 1458 to make it bias closer to its operating range. (These things don't go lower than 2v.)

Would you please clarify what should be done in order to add biasing to pin 3 of the 1458? Haven't got it.

[idy]

Take a 100k pot. Attach the CW terminal to 9v somewhere on the board. Run a wire from the wiper to pin 3 of the 1458. There is already a 22k from pin 3 to ground (if you can find which one, you can attach your wire to the side attached to pin 3), you should see now about... less than 2v when the pot is set to CCW. As you turn it up you should approach 2v. Somewhere you will get the LED to light with no signal. (and with sensitivity maxed). You want it just below that point, so the detector is "on the edge." When (if) you get that to happen you can pick a resistor (or solder two together) to approximate that value.

You may also (if you have socketed the ics) try other Op-amps. I think we found the 358 (?) worked better... read the thread back a few pages. Spellbinding.

[telebiker]

I had no luck with biasing, the sound still was clear unprocessed guitar. Will get some op-amps and share the results. Thanks for help!

[idy]

If the LEDs are lighting up, the 1458 is not your problem. All it does is transform the signal into DC to drive the LED. Somehow your filter is not working.

Double checked all values of resistors around the tl074?

Double checked and reflowed solder joints?

[idy]

Are you sure you have the send/return jacks correct? I know I did them backwards first time.... I thought the send would be close to the input and the return close to the output, but no.

[telebiker]

For now having send and return hardwired, don't have jacks yet while testing.
Checked resistors values visually near TL074 and they look good. On the PCB 220k shows 17k; 120k shows 4.8k; 1.8M shows 1.2M, but that's probably due to internal PCB connections.

The most interesting part are LDRs. In the light environment one shows 4k and the other 6k, while in the dark they are 71k and 123k. So I'm having 2 different LDRs (probably Futurlec PHOTOCELL2 and PHOTOCELL2A). I believe this is not correct at all and LDRs are supposed to behave in the same way. Could this cause the filter not working?

[idy]

When you measure the LDR in circuit, they have parallel resistors to set their dark resistance below the multi mega-ohm level they have naturally, and those resistors are different:220k and 120k. So you should see different values. But having different kinds of LDR won't help the filter be "focused." Could be worth while to match them. Still that probably isn't your problem.

You should trace the signal. You did that up to the 1458 and heard the "rectified" signal, but the filtered signal isn't getting to the "blend" pot. We need to know where it vanishes. Is it getting to the filter IC? If the filter wasn't triggering you would still hear a signal from the CW side of the pot but it would be from a filter that is "stuck" and sounds bassy or tinny but won't sweep. If there is no sound, something is wrong.  The voltages tell us the tl074 is power up, but where is the signal dying?

[telebiker]

If the filter wasn't triggering you would still hear a signal from the CW side of the pot but it would be from a filter that is "stuck" and sounds bassy or tinny but won't sweep.

That's exactly what I hear on the CW side of the blend pot.

[telebiker]

At what points should I hear filtered sweeping signal?

TL074 gives me the following sounds:
01: very quiet clean signal, probably there's little bit of sweeping
02: quiet clean signal
03: quiet clean signal
04: distorted signal
05: no sound
06: no sound
07: quiet clean signal but louder than in 2 and 3
08: clean
09: no sound
10: no sound
11: no sound
12: clean
13: clean
14: clean

[idy]

Are you trying to read the schematic at all? even if you don't really understand them you can follow the signal and start to learn.

TL074 power pins are 4 and 11. Funny you are getting signal on pin 4. Should not be happening.

12,13,14 are the input buffer. So good your signal is there.

The other three Op Amps have outputs 1=highpass, 7=bandpass, 8=lowpass. So those pins should sound like that. Just flipping the sweep (up/down) switch should turn the LEDs off and on and give you the  top and bottom of the sweep.
But funny that you getting something on these but nothing on your blend pot...that shouldn't be. The hp/bp/lp switch just chooses one of these three to go to the CW pin on the blend pot. How can there be something on 1,7,8 but nothing on the blend pot?

You should get pretty much the same signal on 14 and 2. I think you should trace it through the two big caps before send and after return and through that 10k attached to pin 2.

I took the trouble to hook one of mine up. The signal on 14 and 2 are the same level. The other 2 outputs are also strong.

[idy]

I do hear weak signal on pin 4, +power, so that is not bad. I don't understand it but it's not your problem.

It is normal to hear nothing in pins 5 and 10, as those are inputs tied to "vref" the mid voltage that biases the Op Amps.

I hear strong signal on 1,7,8 and the buffer. Other pins weak or nothing.

[telebiker]

Thanks for your patience! Trying to read the schematics. Sorry, for me it's not so easy.

But funny that you getting something on these but nothing on your blend pot...that shouldn't be. The hp/bp/lp switch just chooses one of these three to go to the CW pin on the blend pot. How can there be something on 1,7,8 but nothing on the blend pot?

Not exactly, sorry if I confused things. I meant that I had this: If the filter wasn't triggering you would still hear a signal from the CW side of the pot but it would be from a filter that is "stuck" and sounds bassy or tinny but won't sweep.

I traced the audio path from pin 14 to pin 2 of the TL074 and found that on the other side of 10k resistor (which is near pin 2) signal gets weaker. Going to replace that resistor.

[telebiker]

I was wrong about resistors when I checked them. I noticed that I have 10.5k resistors wired instead of 10k. Could this cause the issue?

[idy]

Do try an LM358 in place of 1458 if you can. I found not all 1458's worked. I tried from different brands with different results. My hunch is that the original guys had a set of components that worked just barely in this somewhat hacked together design. I don't remember if the LEDs lit up when the OpAmp was the problem....