Erica Synths mki x es.EDU module build/debugging

I’m having a problem with my S&H/noise module that I just built.

When I apply a trigger to the Clock In, the S&H samples the noise, but instead of holding, or even drooping, the voltage slowly rises.

I’ve reflowed all the joints in the upper left (upper right from the jack side) part of the pcb, no solder bridges, and it’s still happening.

I replaced R27 as I thought it might be the culprit due to the resistor sitting so close to the board, I thought maybe the solder didn’t reach both sides of the hole in the pcb, but that didn’t change anything either. I also replaced the TL074 with anther I had on hand, no change. I"m at a loss as to why the voltage would slowly increase at all

Here’s a link to the manual/build guide, and the schematic is on page 60

Additional detail, the S&H out seems to linearly rise to 10.9v

I’m measuring -9.7v at TP5 (E) and 2.8v at TP4 (D).

Any ideas?

Update, I figured this out.

My kit came with a TL072CN for the slew circuit op amps. I swapped it out for a TL072CP that I had, and the problem is resolved.

I do not know if that means the CN is inappropriate and the kit came with the wrong op amp chip, or if the TL072CN that came with my kit is just faulty. I will email Erica Synths to determine if it was the wrong chip, but looking at the coding it seems as though they are roughly equivalent.

Thanks for posting this thread! Has anyone else had trouble building the power supply for the case? I’m having difficulty getting a clean solder joint on the two central pins of the small black box, and either for that reason or another, nothing’s working.

I haven’t built the DIY case myself (I had another case and power supply I built already) but it might be helpful for you to post pictures to point out exactly what joints you are referring to.

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Sorry for the delay! Been away and just got home. Here are the ones I mean. You can see my joints are pretty messy, though I was using the exact same technique as the other joints around it - I wonder if there’s a big heatsink or something inside the black box?

that’s quite possible, or just the whole ground layer which has a big thermal mass.

apply more flux and increase heat & duration for those specific joints.
as a reference i use rosin-core leaded solder and usually solder at 240-270°C (depending on components). i can go up to 300-320°C for those big thermal mass use-cases.

on flux: select one appropriate w/ the type of solder you use. i use Chip Quik products.

on solder: “quality” solder helps. whether you use lead or lead-free, try to find an “eutectic” one, i.e. which solidifies nearly instantly (producing clean joints more easily). on leaded solder they achieve this w/ adding silver to the composition. idk about lead-free variants.

I’m using Stannol Kristall 611 lead-free solder at about 300C and I’ve recently picked up a Flux-Stift 500-6B, so hopefully a bit of that will help. Will give it a try and report back! Thanks for the tips.

Edit because I cant post another response in reply to myself:
@eigen No dice - despite cleaning up those joints quite a bit. Still no LED light or power at all, I’m surprised as it’s a relatively simple build. I’ll drop Erica a line I guess…

Edit 2:
Actually, it does work! I’m getting power on the connectors, just no LEDs. Maybe I burnt them out somehow? I’ll try replacing.