great!!@!! im glad you found the solution!!
Went googling earlier, and the only photo of a transparent PCB I could find was from Mikeās Electric Stuff where he showed one on top of a workbench that was so beaten up that I couldnāt quite tell what I was looking at 
Transparent solder mask is a thing, but probably special order and non-trivial setup costs.
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Iāve never seen any! Would look cool but maybe confusing to solder?
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I have a PCB of Mikeās in my desk drawer, specifically designed for making vintage printers and photocopiers play music!
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nice! yeah when I started this I was gunna try no silkscreen at all. but the world of hurt for people soldering made me think twice, you cant beat the classic look, trying to find a fabricator with yellow boards, no solder mask and pink silkscreen was near impossible hahaha.
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thats cool! is it digital?
Hey everybody! Just finished soldering my module but unfortunately I dont get any sound:-( Is it normal, that the upper leds are always somehow on, although the on-switch is switched off? I hooked the module up to my audio-interface as an external effect but i only get sound when the module is turned of. The module is powered by an external 12 V power supply. As far as I understand the schematics, -12 v is not needed in this case, right?
Do you have any ideas where to start debugging? I checked every value twice before soldering it in. 5 V works and is at least connected to the PT2399 (got these things from china). Many thanks in advance, everybody!
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-12V is used by the op amp.
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wow, that was quick! than this might already be the problem, right?
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It certainly is A problemā¦
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I think the lack of -12v would explain the behaviour your explaining as the timing circuit goes through an opamp that needs the -12v supply. without it I can imagine the transistor is causing the circuit to go to ground, and if it goes past what its set in the circuit the pt2399ās turn up with the LEDās stuck on as it hasnāt turned on correctly. so yeah it sound like you probably have a working module! just not plugged in the -12. do you have a eurorack power supply? or was hoping to use this as a pedal or something?
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nice!!! glad the mod is doing its thing!!!
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many thanks for your answer. unfortunately i was hoping to use it as an external effect without owning a eurorack system. maybe i should have checked the schematics more in detail! But i dont see this as an issue, more than a chance to build a small effects rig now:-) tried to hook the module up to a pc power supply providing +12 and -12 v but still nothing realy to get out, just clipping noises. i will order a eurorack power supply and hope, that this will solve the problem. or might this be related to the 2399s?
Iām stumped. My build seems to be working, except none of the signal LEDs light up beyond a very (very) faint flicker. Is there any single component that would make all four not light up? I tried switching out one transistor thinking maybe Iād fried them all somehow, but no difference. When I try to measure the voltage coming to the LEDs, itās just around 1v whereas the on/off LED is seeing around 2v (and working).
My ātimeā LED is quite faint, and the three channel LEDs are brighter but still much fainter than the āonā LED.
The LEDs care about the current, not the voltage. The āonā LED connects to +12V through a 1k resistor. The time and channel LEDs each connect to +12V through a 100k(!) resistor and a transistor. So I guess itās no surprise their maximum brightness is lower. Iām surprised he used such a high resistance. You could presumably swap those out for something lower, obviously 1k isnāt a problem.
I even tried a 470 Ohm in parallel with the 1K on one of them with no discernible difference, so Iām thinking something else is up. And the amount they light up is really almost invisible.
The 1k is on the base of the transistor. What affects the LED brightness is the 100k resistor on the collector, connected to +12V. I wouldnāt go directly to 470R for that one, might be too low. My time LED is close to invisible at least at the current settings, and of course different LEDs will give different results.
Ah, makes sense. I was thinking the 1K was what might be too high. Iāll play around. Thanks!
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As long as mine makes abominable noises Iām happy.
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