Sea Horse - No Chorus, Only Delay

[Dirty_Boogie]

Just completed my Sea Horse (latest generation PCB) and in my preliminary boxing, found that there is no modulation. The Dimension gives slapback echo, the Depth appears to be working, and when I turn the Animate and Intensity knobs, they give the impression that chorus wants to happen (but only when turning the knobs.) The Rate and Shape have no effect, so my guess is the LFO is not working. I unfortunately don't have another PT2399 to try (more on order.) Double-checked electrolytics and diode orientation, and all solder points appear to be good. Any ideas?

P.S. Need to reduce the intense brightness of the red LED. Will increasing R31 (1K) to 3.3K have any impact on the sound of the pedal, or is this a CLR only?

 

[stevtron]

Maybe that helps ...

Sea Horse wrong schematic?

I think the schematic had a little problem, the pin 3 of INT pot should not be connected directly to the LED(D1), instead, it should be connected to the point between R31 and IC4.2's Output(Pin 7), so the Vf of LED won't effect the oscillator, and you will get a really tiny effect if you don't...

forum.pedalpcb.com

 

[stevtron]

Changing the RLED will not have impact on the sound itself, no problem …

 

[Dirty_Boogie]

Maybe that helps ...

Sea Horse wrong schematic?

I think the schematic had a little problem, the pin 3 of INT pot should not be connected directly to the LED(D1), instead, it should be connected to the point between R31 and IC4.2's Output(Pin 7), so the Vf of LED won't effect the oscillator, and you will get a really tiny effect if you don't...

forum.pedalpcb.com

Thanks Stevtron. I did check with PedalPCB that the recent batch of PCBs (I just received mine) were the corrected boards before I started building mine, so I don't think that's it. But, I'm really hoping that they did in fact check the new Sea Horse boards when they came in.

 

[zgrav]

If you are getting echo it seems like your 2399 chip is likely OK. Since you can get a chorus effect when you rotate one of the pots I think you are right that the LFO is not working, since that should be sending a varying signal to the 2399 chip. I am not familiar with the circuit design for the LFO in the build docs, but that seems to be the place to start checking.

Given that the circuit diagram shows different voltages being fed into the + and - inputs of a couple of the op amps, the LFO seems to be designed around a comparator circuit. I did a google search and found a article where someone is explaining this type of design for a Tremulus Lune pedal. You might want to read through it and get some ideas for things you could check in your circuit to troubleshoot it. https://mimmotronics.com/blog/talk-theory-to-me/tttm4/ I was not familiar with that site, but I bookmarked it as a good DIY resource.

And aside from the theory, you can use your DMM to check the connections for the parts in the LFO section to search for something that has a bad connection or a wrong part.

 

[stevtron]

With shape, depth and intensity pots hard right you got no mod signal ? (speed ca. 9 o'clock)

 

[Dirty_Boogie]

With shape, depth and intensity pots hard right you got no mod signal ? (speed ca. 9 o'clock)

Correct. Even with everything maxed, Rate and Shape have no effect.

 

[Robert]

Is your LED pulsing? It's hard to tell because of the tape, but it doesn't appear to be.

If not, that's a sign that the LFO isn't modulating.

 

[Dirty_Boogie]

Is your LED pulsing? It's hard to tell because of the tape, but it doesn't appear to be.

If not, that's a sign that the LFO isn't modulating.

Nope, no LED pulse. But I think I burned my corneas just looking at that thing! Still seeing a red dot everywhere I look. LOL!

So, as I also suspected, the LFO isn't working. How would you go about troubleshooting this?

 

[zgrav]

1. Identify the LFO section in the circuit diagram in the build documents that is built around IC4. Confirm you are getting power at the parts for both VCC and VrefB because you need those to be different for the LFO to work. If you are getting power where you are supposed to, then touch up all of the solder connections of the PCB for the LFO parts, including the IC.

2. If that did not get the LFO working, swap out IC4 if you have a replacement and see if that works.

3. Next thing to try would be to confirm the part values for the parts of the LFO are correct and use your DMM to make sure the parts are connected on the board as provided in the circuit diagram, including connections to ground.

Somewhere along those steps your LFO should start working.

 

[Dirty_Boogie]

1. Identify the LFO section in the circuit diagram in the build documents that is built around IC4. Confirm you are getting power at the parts for both VCC and VrefB because you need those to be different for the LFO to work. If you are getting power where you are supposed to, then touch up all of the solder connections of the PCB for the LFO parts, including the IC.

2. If that did not get the LFO working, swap out IC4 if you have a replacement and see if that works.

3. Next thing to try would be to confirm the part values for the parts of the LFO are correct and use your DMM to make sure the parts are connected on the board as provided in the circuit diagram, including connections to ground.

Somewhere along those steps your LFO should start working.

Thanks, will work on these suggestions later. I did try different LM324 and TL074 IC's, but those made no difference.

 

[tdukes]

My seahorse lfo started working after replacing one of the capacitors.

 

[zgrav]

Congratulations. Looks like that should be a pretty cool chorus.

 

[Dirty_Boogie]

Found it!! One (or maybe more) suspect solder point on IC4. Thanks all for your input. This truly is a wonderful chorus - from subtle to super-trippy.

Wait... I just realized that the "Dimension" delay is now gone. Earlier (when I had the LFO issue) I had it range from one one slap-back, to complete oscillation, as I showed in my original video. Now, just one slapback, regardless of the Dim knob position. Ugh, have to pull it apart again...