Electrovibe not vibing

[ThisIsAlec]

Hi all,

I just finished my electrovibe build and the thing isn’t vibing. I get a slight drop in volume when the vibrato is engaged and minor tone change when the chorus is engaged otherwise it sounds like it’s bypassing. Any ideas?

Thanks!

 

[micmac]

Is the lamp flashing? Did you try it in the dark (with the case closed)?

 

[ThisIsAlec]

Hi Micmac,

The lamp is flashing nice and bright, but only when the gain is turned clockwise about 3/4 of the way. If I turn it any counter clockwise it stops flashing altogether.

And yes, I tried it with the lid on with no change. The LDRs are doing their job - I tested with an audio probe and they are warbling as expected immediately after the LDR in the audio path. However, once I test past the 4.7k resistor that sits immediately after the LDR on the audio path (R31, R41 R47 and R53) the oscillation is completely gone from the signal and it sounds dry and clean. This seems to happen after each LDR, which would explain why the output signal sounds awfully similar to the input - the effect of the light and LDRs appears stripped from the audio path.

Any ideas o' brain trust?

Thanks!

-Alec

 

[ThisIsAlec]

Hi Micmac,

The lamp is flashing nice and bright, but only when the gain is turned clockwise about 3/4 of the way. If I turn it any counter clockwise it stops flashing altogether.

And yes, I tried it with the lid on with no change. The LDRs are doing their job - I tested with an audio probe and they are warbling as expected immediately after the LDR in the audio path. However, once I test past the 4.7k resistor that sits immediately after the LDR on the audio path (R31, R41 R47 and R53) the oscillation is completely gone from the signal and it sounds dry and clean. This seems to happen after each LDR, which would explain why the output signal sounds awfully similar to the input - the effect of the light and LDRs appears stripped from the audio path.

Any ideas o' brain trust?

Thanks!

-Alec

Also, checked resistor values and the pots have covers ...

 

[PunchySunshine]

Hi all,

I just finished my electrovibe build and the thing isn’t vibing. I get a slight drop in volume when the vibrato is engaged and minor tone change when the chorus is engaged otherwise it sounds like it’s bypassing. Any ideas?

Thanks!

At first glance, that's a lot of socketed transistors IMO. Sure makes for a bunch of possible points of failure.
Secondly, check this switch connection I've marked to make sure it's not bridged.

 

[ThisIsAlec]

I've audio probed all of the socketed transistors and they're good to go. I also saw that potential bridge and fixed it up. Still same ol' situation. This has got to be something obvious, right?

Maybe the power source? I'm getting 12v not 15v at the transitors and the lamp isn't lighting up until the trimmer is turned nearly entirely CCW. I have switched out the charge pump and regulator to no avail.

 

[Fontelroy]

I was gonna say, try a new charge pump and regulator... where did you get yours?

 

[ThisIsAlec]

Tayda. I can test the regulator but not sure how to test the charge pump.

 

[ThisIsAlec]

Update: I had switched the 250k and 500r trimmers, which fixes the light issue. So now it’s just that the warble from the LDRs seems to get “removed” from the audio chain, even though the signal passing through the LDR definitely modulates as intended.

 

[micmac]

Hi Alec,

I have a stock Electro Vibe, no mods, which is working. If you want me to measure anything with a DMM let me know. Happy to help.

Kind regards,
Seb

P.S.: I also have an audio probe. Can try stuff out with that, too.

 

[ThisIsAlec]

Hi Alec,

I have a stock Electro Vibe, no mods, which is working. If you want me to measure anything with a DMM let me know. Happy to help.

Kind regards,
Seb

P.S.: I also have an audio probe. Can try stuff out with that, too.

Amazing offer, thank you! Do any of these look odd to you? (https://docs.pedalpcb.com/project/ElectroVibe-PedalPCB.pdf)

IC4 (LT1054):
- pin 1 - 8.8v
- pin 2 - 4.8v
- pin 3 - 0
- pin 4 - 0
- pin 5 - 200mv
- pin 6 - 2.5v
- pin 7 - 1.4v
- pin 8 - 1.35v

IC1 (L78L12)
- pin 1: 16.2v
- pin 3: 12.1v

Q1:
- pin 1: 0 to 7.5v (oscillates)
- pin 3: 16.5v

Q2
- pin 1: 0 to 6.1v (oscillates)
- pin 3: 16.5v

Q3:
- pin 1: 3.1v to 3.9v (oscillates)
- pin 3: 6.2 to 9.5v (oscillates)

Q4:
- pin 1: 3.8v - 4.6v (oscillates)
- pin 2: 0 to 6.2v (oscillates)

Q5:
- pin 1: 1.25v
- pin 3: 3.4v

Q6
- pin 1: 208v
- pin 3: 9.1v

Q9, 11, 13
- pin 1: 4.2v
- pin 3: 12v

Q8, 10, 12
- pin 1: 2.8v
- pin 3: 9.2v

 

[micmac]

Hi Alec,

below mine. I added Q14 and Q15.

Please note that my LT1054 pin 1 is lifted (because my PCB has pin 1 and 8 shorted; not that I needed to lift the leg, was just a bit superstitious I guess ).

Measurements taken on Speed 1 (Speed 1 LED on), no input/output cable connected, all pots at 50% (12 o'clock).

Are you sure you only get 1.35V on pin 8 of the LT1054?

IC4 (LT1054):
- pin 1 - 8.8v on pcb (0.8v on lifted leg)
- pin 2 - 4.75v
- pin 3 - 0
- pin 4 - 0
- pin 5 - 200mv
- pin 6 - 2.5v
- pin 7 - 1.4v
- pin 8 - 8.84v

IC1 (L78L12)
- pin 1: 16.3v
- pin 3: 12.2v

Q1:
- pin 1: 5 to 8v (oscillates)
- pin 3: 16.7v

Q2
- pin 1: 4.7 to 7.5v (oscillates)
- pin 3: 16.7v

Q3:
- pin 1: 2.9v to 3.9v (oscillates)
- pin 3: 13.6 to 14.6v (oscillates)

Q4:
- pin 1: 3.5v - 4.6v (oscillates)
- pin 2: 13.6 to 14.6v (oscillates)

Q5:
- pin 1: 1.25v
- pin 3: 3.25v

Q6
- pin 1: 2.68v
- pin 3: 9.34v

Q9, 11, 13
- pin 1: 3.4v
- pin 3: 12.16v

Q8, 10, 12
- pin 1: 2.82v
- pin 3: 9.3v

Q14
- pin 1: 4.32v
- pin 2: 12.16v

Q15
- pin 1: 0.72v
- pin 2: 1.83v

 

[ThisIsAlec]

Hi Alec,

below mine. I added Q14 and Q15.

Please note that my LT1054 pin 1 is lifted (because my PCB has pin 1 and 8 shorted; not that I needed to lift the leg, was just a bit superstitious I guess ).

Measurements taken on Speed 1 (Speed 1 LED on), no input/output cable connected, all pots at 50% (12 o'clock).

Are you sure you only get 1.35V on pin 8 of the LT1054?

IC4 (LT1054):
- pin 1 - 8.8v on pcb (0.8v on lifted leg)
- pin 2 - 4.75v
- pin 3 - 0
- pin 4 - 0
- pin 5 - 200mv
- pin 6 - 2.5v
- pin 7 - 1.4v
- pin 8 - 8.84v

IC1 (L78L12)
- pin 1: 16.3v
- pin 3: 12.2v

Q1:
- pin 1: 5 to 8v (oscillates)
- pin 3: 16.7v

Q2
- pin 1: 4.7 to 7.5v (oscillates)
- pin 3: 16.7v

Q3:
- pin 1: 2.9v to 3.9v (oscillates)
- pin 3: 13.6 to 14.6v (oscillates)

Q4:
- pin 1: 3.5v - 4.6v (oscillates)
- pin 2: 13.6 to 14.6v (oscillates)

Q5:
- pin 1: 1.25v
- pin 3: 3.25v

Q6
- pin 1: 2.68v
- pin 3: 9.34v

Q9, 11, 13
- pin 1: 3.4v
- pin 3: 12.16v

Q8, 10, 12
- pin 1: 2.82v
- pin 3: 9.3v

Q14
- pin 1: 4.32v
- pin 2: 12.16v

Q15
- pin 1: 0.72v
- pin 2: 1.83v

This is incredible and took a ton of work, thank you! Your thinking on pin 8 was right: it was pushed in a little too far and missed the socket. The voltages on Q3 and Q4 also helped me realize I was biasing things all sorts of backwards. Between the two we have a functioning, happy electrovibe.

I cannot thank you enough! This community rocks, MicMac chief among them.

-Alec

 

[micmac]

And there I was, thinking it was only a typo

Good job on finding the issue that quickly!