DELAY REBOTE 3 - Troubleshooting

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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Gebrey
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Post by Gebrey »

Hello everyone,
I started advanced projects since I crafted tons of simple and intermedium pedals and amps.

This is a really challenge since there are a lot of components.

Here the schematic:
20240804_173822.png
Here my DIYLC layout:
20241007_172204.png
Here the bottom DIYLC of the board already flipped & real pcb bottom
ZomboDroid_07102024052718.jpg
Here a comprehensive photo of the setup:
20241007_171419.jpg
It doesn't work properly.
The diagnosis:
- original signal pass unprocessed like expected
- delay signal is very very very low in volume (need to crank amp at 11 to hear something mixed with bckgnd noise)
- if I connect the output to the 12pin or the 16 pin of PT2399 chips, the sound came out very low and artifact but it came, 100% delay only
- pt2399 #3 is warmer than the others. Its almost hot (50°C?) and no output from pin 12. Strange.
- voltages are correct: 9v and 0v to tl072 (pin8&4) and 5v and 0v to PTs (pin1&3/4)
- checked 3 times the circuit for errors. Nothing.

ICs and rest of components are all from Aliexpress.
TL072 are verified working.
Resistor chekced with MMeter before use.
PTs first time I use them. But they can delay sound as checked.

I ask you to check errors in schematic<>layouts<>pcb and suggest me some test to do to exclude components.

I will swap these PTs with other from the same order. And eventually after some try I will buy them from a trusted source.

Thanks in advance guys

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Gebrey
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Post by Gebrey »

Well, I think that Ive found the issue.

Im first, sorry to have posted in wrong section... but since Ive redone layout could be more easy to find here.

Feel free to move it

After some checks, Ive used a PT2399 echo module as a socket board for PT2399 working check. They work as expected.

So.... something hit my mind. Ive used 78L05 (0.1A) instead of L7805 (1.5A). In my mind the IC consumes 30mA but datasheet says 100mA.
So probably 100mA for 3 IC is too much, maybe in rebote 2 works.

Unfortunately Ive not L7805 avaible right now. Tomorrow Ill probably feed 5V with external circuit to confirm the issue.

But checking with scheme is the only difference. Sounds come at the output very low. So probably is that, the traces are right and the layout too.

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Gebrey
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Post by Gebrey »

tonepad_rebotedelay2501587ff7-186a-4e1b-9688-0a1ac0b4a019_00000_updated.png
Here the schematic of Rebote 2.5 that confirm they (rebote 1, 2 & 2.5) still use 78L05 and 2x PT2399 can be handled by 0.1A regulator.

Since the scheme for rebote 3 specifies L7805 (1.5A) Im confident that's the error.

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Gebrey
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Post by Gebrey »

Unfortunately L7805 change something but not at all. In fact the low volume delay I could probe from OUT PT2399#1 and PT2399#2 NOW is coming out from PT2399#3 and out from pedal output, confirming that the 78L05 100mA was not suitable for this pedal.

Now, if I bypass R12 or R20 nothing changes. Seems that INPUT received by PT2399#1 is to low to trigger properly the delay chip.

Please help me Guys

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J4mes
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Post by J4mes »

Don't be disheartened. There are so many projects on here that people don't have time to debunk everything or dedicate time to something that they can't physically fix.

Based on your soldering, I'd strongly recommend getting yourself a solder sucker cheap online.
Remove the globules of solder and re-solder. When soldering, ensure you heat both the component and the pad. Make sure all components are clean or a touch of flux, but be sure to remove excess with rubbing alcohol. When your joints are nice and you can see where everything should go, you can clearly see any bridges or faults.

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