EQD Space Spiral doesn't do anything

[Maximiliaan]

Hey,

I've just finished assembling the following circuit:
http://dirtboxlayouts.blogspot.com/2020/06/earthquaker-devices-space-spiral.html
https://docs.pedalpcb.com/project/DarkRiftDelay.pdf

I used the stripboard layout shown, which should work according to the comments. However, mine does nothing at all. The signal gets through clean, but there is no delay at all. I've checked for shorts and triple checked that all components and connections are ok.

I get the following voltage readings:
Source Voltage: 8,93V

PT2399:
1: 5.00V; 2: 2.50V; 3: 0.00V; 4: 0.00V; 5: 3.80V; 6: 2.50V; 7: 0.20V; 8: 0.62V
9-12: 2.50V; 13: 0.00V; 14: 5.00V; 15-16: 2.50V

LM324:
1: 4.32V; 2: 3.85V; 3: 4.32V; 4: 8.64V; 5: 4.23V; 6: 4.32V; 7: 4.33V
8: 4.22V; 9: 0.00V; 10: 4.23V; 11: 0.00V; 12: 4.12V; 13: 4.21V; 14: 4.21V

LM833:
1: 2.50V; 2: 2.50V; 3: 2.46V; 4: 0.00V
5: 2.44V; 6: 2.51V; 7: 2.51V; 8: 8.65V

TL072:
1: 4.30V; 2: 4.30V; 3: 1.81V*; 4: 0.00V
5: 4.22V; 6: 4.31V; 7: 4.31V; 8: 8.65V
*starts at around 2.4V then drops slowly to 1.81V


Is there anything that could explain why this circuit fails? I was thinking that maybe one of the IC's is bad but I switched them all and it was still the same. I also read that these PT2399 can be unreliable but I tested them in another circuit before and they worked there.

I did notice that my IC's are labeled LM324N, LM833N and TL072CP. Do these letters at the end matter somehow?
Any suggestions would be more than welcome

[moid]

Hi there
I am looking at this image on my phone, so I may be wrong but on the solder side of the vero in the bottom left hand corner it looks to me like there are thin threads of solder connecting the second row up from the bottom with the rows above - very close to your finger. The fourth row up in that corner looks similar. I think I can see an unsoldered component nine rows down from the top and about 14 holes from the left in a cut.
Have you tried running a sharp knife down all the rows between the copper strips? I have fixed circuits before that had thin threads of solder that were invisible to the eye, but caused shorts.

[Maximiliaan]

Hey, thanks for replying.

I checked the rows in the left bottom corner again but there are no unwanted connections. Tested it with a multimeter. Row 4 and 5, counted from the bottom, have to be connected in any case and row 4 and 3 don't connect.

I checked the other suggestion about a loose component but it's just a leg that I didn't cut very short. Just looks weird on the picture.

[Transistor-Transistor]

I know this most likely isn't the problem but do you have the circuit bypassed?
If not, is the output clean signal colored at all? That would help narrow the problem down a bit.
Also the mix knob could be all the way down 

[Maximiliaan]

I have this test pedal that has a wired footswitch and alligator clips that I use to test all my circuits.

I did another test just now and the output signal of the board sounds the same as the clean signal, although at high volumes I just noticed that there is a single repeat that is really quiet and very distorted. Also doesn't react to any of the pots, including the mix, which is kinda weird.

It feels like I have a bad component somewhere but I can't tell which one

[Ice-9]

I'm just quickly looking at the schematic from your link and the output of IC2.1 pin15 isn't connected to anything, and I can't see any signal going into the PT2399 delay chip on this diagram either. I don't know if your layout follows this diagram but that would not help much if it does.

IGNORE WHAT I SAID.

I didn't notice that the PT2399 has been drawn in separate parts and IC2.1 is part part of the PT2399 input section. Sorry I totally missed that. 

[ElectricDruid]

Have you got an audio probe? If not, knock one up quick! - http://diy-fever.com/misc/audio-probe/

Then test:

IC1/TL072 pin1, the buffer output. Have you got clean signal?
IC2/PT2399 pin15, the mixer output. Have you got clean signal?
IC3/LM833 pin 7, the post delay filter. Have you got delayed signal?
IC3/LM833 pin 1, another post delay filter. Have you got delayed signal?

Finding out how far it gets should help us narrow the problem down a bit. The voltages all look ok.

BTW, the extra letters after the number in the IC name usually refer to the package type (so DIP versus SOIC versus TSSOP or whatever) and/or the temperature range (industrial, automotive, millitary, etc). There's no standardisation of these between manufacturers, unfortunately. There'll be a key for them in the back of the IC's datasheet somewhere.

[Focalized]

I think it's going to be really hard for anybody to see a soldering mistake if any, especially with the underneath jumpers blocking things. Curious why you did that. And why your wires aren't through the holes. Some of them look bad.

[ElectricDruid]

One more thing: I strongly recommend cleaning up your veroboard with a pan scourer and a bit of washing-up liquid before use. Give it a good scrub and get all the tarnish and grease off it, and then rinse it with clean water and dry it off and you'll get better joints.
Perhaps it#s just the lighting on the photo, but those copper strips look very dark and dull.

[duck_arse]

I get the following voltage readings:
Source Voltage: 8,93V

PT2399:
1: 5.00V; 2: 2.50V; 3: 0.00V; 4: 0.00V; 5: 3.80V; 6: 2.50V; 7: 0.20V; 8: 0.62V
9-12: 2.50V; 13: 0.00V; 14: 5.00V; 15-16: 2.50V

LM324:
1: 4.32V; 2: 3.85V; 3: 4.32V; 4: 8.64V; 5: 4.23V; 6: 4.32V; 7: 4.33V
8: 4.22V; 9: 0.00V; 10: 4.23V; 11: 0.00V; 12: 4.12V; 13: 4.21V; 14: 4.21V

leaving those pins 13 and 14 on the PT unconnected is probably a very bad idea on the part of the designer, but what do we know? both those pins ought to be about the same as pin 2, 1/2 the 5V. perhaps a hidden short on pin 13?

and - if pin 9 of the LM324 is really 0V, you have a problem there. [my pdf viewer doesn't magnify past 400%, so I have no way of reading pin numbers on that circuit diagram.]


ahhh, helpfully, the circuit diagram doesn't match the layout, at least as I look at it. I thought pins 8 and 9 were to be shorted together as in the DarkRiftDelay doc, but that doesn't seem to be the case on the vero.

I give.

[ElectricDruid]

ahhh, helpfully, the circuit diagram doesn't match the layout, at least as I look at it. I thought pins 8 and 9 were to be shorted together as in the DarkRiftDelay doc, but that doesn't seem to be the case on the vero.

Dammit!! So we've been supplied with a schematic that's not the same as the layout we're looking at?! I *hate* layout sites where they don't link to the actual schematic they used. It's a royal pain in the backside. How's anyone supposed to debug anything like that? That's literally item 2 on the "What to do when it doesn't work" list, right after the name of the thing!

LM324 is the LFO though, so until we get the delay working, I wasn't going to worry about that part.

[Maximiliaan]

Then test:

IC1/TL072 pin1, the buffer output. Have you got clean signal?
IC2/PT2399 pin15, the mixer output. Have you got clean signal?
IC3/LM833 pin 7, the post delay filter. Have you got delayed signal?
IC3/LM833 pin 1, another post delay filter. Have you got delayed signal?

Just did this test. TL072 pin1 and PT2399 pin15 both give the clean signal.
The LM833 pin 7 and 1 both give a very weak and heavily distorted delay. I can only hear a single repeat. It does respond to the time pot though, so that's something I guess. I swapped it with another LM833 but it gives the same results. Does this help?

I'm so sorry about the schematic apparently using different pin numbers on the LM324 But since this IC is just 4 opamps, I guess the final circuit is still the same, right?

[Transistor-Transistor]

Could the bias on the lm833 be off?

[antonis]

Could the bias on the lm833 be off?

Taking into account PT2399 pin12 out 2.5V, LM833 DC voltages are fine..

[ElectricDruid]

Just did this test. TL072 pin1 and PT2399 pin15 both give the clean signal.

Ok, so the signal is getting *into* the PT2399 ok. That's a good start!

The LM833 pin 7 and 1 both give a very weak and heavily distorted delay. I can only hear a single repeat. It does respond to the time pot though, so that's something I guess. I swapped it with another LM833 but it gives the same results.

Ok, so either the PT2399 isn't working, or there's something up with that filter. a single repeat is what we expect, so that's fine. And if it responds to the Time pot, then the PT2399 is doing something at least!

Does this help?

Yes, i think it does, doesn't it?. You could try testing pin 12 of the PT2399 next. That's the direct output from the PT2399. If that's ok, then the problem is the filter. If that's bad, the problem is probably around the PT2399 somewhere.

I'm so sorry about the schematic apparently using different pin numbers on the LM324 But since this IC is just 4 opamps, I guess the final circuit is still the same, right?

It's not your fault, and I was being grumpy. It annoys me that people put layouts up with no schematic, since it makes them very difficult to debug. You *always* need a schematic!
As you say, the circuit will be the same, but they've re-arranged which amps within the package they used to make the layout easier. Hopefully the LFO is ok anyway and then we won't have to care about that!

[Maximiliaan]

I tested pin 15 of the PT2399 and it sounds the same as the LM833. A single delay that is distorted and very quiet.
Does this mean the PT2399 is bad?

[ElectricDruid]

I tested pin 15 of the PT2399 and it sounds the same as the LM833. A single delay that is distorted and very quiet.

Ok, so there's no decent signal getting through the delay chip.

Does this mean the PT2399 is bad?

No, not necessarily. More likely it means there's a problem in the circuitry around the PT2399. There's a lot of reasons why the PT2399 might not be happy. Check all the joints on that socket very carefully. It could also be any of those capacitors hanging off the PT2399, so check those and their connections too. I'd be particularly suspicious of C26 and C27 - the modulator and demodulator caps. You said it responds to the Time control, so I'm less worried about the stuff on pin 6; R20, the pot, and R21.

Good luck! We might be close!

[Maximiliaan]

Hey, you were right! The problem was at the PT2399. Now I'm getting very clean delays that respond perfectly to the time, repeats and mix controls. Thank you so much for the the help.

However, there seems to be a problem with the LFO as well because the rate and shape pots don't seem to have any effect. The depth pot does something but barely noticeable. I'll try to go over that section of the circuit and see if I made any mistakes there.

[ElectricDruid]

Excellent work! That's real progress! 

Ok, for the LFO you really need to look at that pin 9 which Duck spotted. It reads 0V. It shouldn't. It needs to be close to half-supply like the others.

[duck_arse]

leaving those pins 13 and 14 on the PT unconnected is probably a very bad idea on the part of the designer, but what do we know? both those pins ought to be about the same as pin 2, 1/2 the 5V. perhaps a hidden short on pin 13?

please retest and repost the voltages on pins 13 and 14. for our records.