Help Troubleshooting Power Issues on Handmade Synth?

[[MBD]]

I posted about this on IG but if any tech heads could help me out, I'd appreciate it.

Turning on the power has been really hit or miss lately and I'm sure that I have the correct plug (9v DC negative). When it does turn on, applying any modulation to either the LFO or either VCO fades in and out. Not like a scratchy pot, more like a power starve.

I didn't build this and the creator is MIA. I'm really illiterate when it comes to electronics so any pointers would help a lot. Thanks.

[housepig]

first suggestion is to open it up, use a bright light and a magnifying glass and look at every soldered connection - is anything frayed or loose, are there any wires or solder bridging connections and making intermittent connections where they shouldn't? sometimes corrosion on circuit boards can create "whiskers" that cause shorts or intermittent connections. check for cold solder joints - compared to a proper joint, it will look dull instead of shiny, and more like a mound than a peak.

[holy ghost]

The power in my old jam space was so shitty that until I threw down for an isolated power supply (a Pedal Power 2 that I’ve had for 10 years now) my effects would sometimes make weird hisses or pings and shit. Might be a super basic suggestion but perhaps changing where it’s plugged in or even changing the power supply might be something worth troubleshooting.

Or also investing in a power bar that prevents ground loops - I did that and my tube amp stopped intercepting a Chinese language radio station….

[duckworship]

that looks like something JMT Synths would've built if I had to guess... I remember a listing for one of their old synths and it had certain "trademarks" of their builds that looked identical to the one you've posted. is that the builder that's MIA or is there someone else?

[-NRRRRK-]

I didn't build this and the creator is MIA. I'm really illiterate when it comes to electronics so any pointers would help a lot. Thanks.

Can you take some gutshots and upload them here?
Also, do you have access to a multimeter?

And last: are you definitely sure about the 9V? Maybe that thing runs on a little more.

[[MBD]]

Thanks for all of the suggestions, to start off, I do have a multimeter I can use along with a soldering iron and various wire cutters and pliers. Hopefully I'll have enough free time this Sunday to open it up and take a look around as well as post some pics if nothing seems outwardly broken.

I am pretty certain about the 9V being the correct voltage, the guy who made this legit carried a One Spot around with him everywhere (again, dude was next level wild). I also have been using a Pedal Power 2 for a while now and it doesn't matter which cable I use or where I plug it in, it's definitely something with the synth itself. It will do the same thing with a One Spot too.

Regarding the JMT resemblance, I thought it was an actual one of theirs when I first saw the listing. I don't know the back story behind this particular synth of his, making things like this was all he really did. I've been out of contact with the guy for years but if I was to guess, I'd say the design was probably all him, I'd even say he probably didn't even know that there is a company called JMT making synths ha!

[[MBD]]

I didn't get the chance to work on it yesterday but I'm trying to find time this week to do so. I may have another local guy who'll help me out and provide some more info.