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Cause & Effect help

Hello! I built a Cause & Effect module from Calsynth. It came with all SMD components presoldered. The remaining LEDs, thonkiconns, switch, and pot seemed relatively straightforward to finish assembling,

Every time I power on the module, the two LEDs start pulsating at a regular pace, maybe 100 BPM or so. None of the subsections seem to work properly. The output on the S&H, for instance, doesn’t hold a stored voltage, and it produces a clock-like output at the same pace that the LEDs are always strobing,

I have no idea why it’s acting like this, Any ideas?

45 Views

aaaaaa

Jul 03

I'm not sure which mode is T&H vs S&H. But in both cases, the LEDs continue to flash at their internal rate, not at the rate set by the signal received at HOLD GATE when patched. In one mode, no signal is output at HOLD OUT regardless of whatever is patched at HOLD IN and HOLD GATE. In the other mode, the pulsating continues at the HOLD OUT regardless of whatelse is patched - the is mostly at zero except for the regular pulses.

Angus Thompson

21 days ago

Gritzner output volume low

My Gritzner module has a low output. PT2399 -> pin 1 = 5.00V U1 -> TL072 pin 4 = 11.3V

U1 -> TL072 pin 8 = 11.3V

U2 -> TL072 pin 4 = 11.19V

U2 -> TL072 pin 8 = 12.5 - 12.6V

U3 -> TL082 pin 4 = 11.3V U3 -> TL082 pin 8 = ( 1..94V and 21.16V )

Knobs @ 12 O'clock, Switches: Main, Squ, A Green is source signal, Blue is output.

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st-modular

Jun 23

Hi Angus,

thanks for the measurements.

The PT2399 pin 1 reading of 5V looks correct, so the 5V regulator is probably working. The first thing I would like to verify is the op amp power rails, because the values you listed look unusual.

The U3 reading is especially suspicious. Pin 8 should be a stable +12 V. If you get readings like 1.94 V or 21.16 V, please double-check the pin numbering, the orientation of the TL082, and whether the measurement was made against GND or against another pin.

Please also check the PT2399 reference voltage:

pin 1: +5 V

pin 2: about +2.5 V

pins 3 and 4: GND

If pin 2 is not around 2.5 V, the PT2399 or its surrounding parts may be faulty.

Please probe the signal at these points:

1. Input jack tip

2. U1 pin 1

3. MIX pot wiper

4. U1 pin 7

5. OUT jack tip after R15

If the level is already low at U1A pin 1, the problem is before or around the input stage.

If the level is good at U1B pin 7 but low at the output jack, check R15, the OUT jack, and possible shorts to ground.

If the dry signal is fine but the delayed signal is very low, please check the PT2399 and the parts around the PT2399 filter/output section.

Also, please make sure to use an original genuine PT2399 chip. Non-original or fake PT2399s are a common cause of low level, noise, unstable delay behavior, or strange modulation problems. If possible, swap in a known-good original PT2399 and test again.

Best,

Stefan

Andrew Kim

June 8, 2026

Pedal Pal Stereo Expression CV Question

Hi everyone,

Just put together a Pedal Pal Stereo. Everything is working as expected, but I am having some issues with the expression pedal connectivity.

I am trying to interface w the expression pedal input on a Meris Mercury X. I checked… exp i/o operates on 0-3.3v and delvers voltage to the ring of the TRS cable. I have a V1 board and all 3 jumpers are in the right place (mine pcb came with a sticker to account for the silkscreen mislabeling).

This is what’s happening:

When I plugin a TRS cable from the expression jack of the pedal it illuminates the CV LED lights when the exp pot is turned cw. When I adjust the exp pot there is no change except at the lower end (ccw) of the dial when the LED dims and pedal responds suddenly. I’ve scaled the expression input in the pedal too…

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Andrew Kim

Jun 09

Dear Stefan, Thank you for your prompt and through reply. Switchign the jumpers did the trick. It appears that the original silkscreen label was correct? Long time time DIYer, but first time pedal user.....I still learing all of the ins and outs. At any rate, Everything now works flawlessly, sounds great. A solid addition to my kit. Thanks again!

Jungle Baxter

June 1, 2026

Solder stencil for Envelope

Does anyone know where I can download a gerber file for making a paste stencil for Envelope? Wanting to cut a stencil for the SMT side of the board only.