Searching for BOSS Dr. Synth DS-330 Service Manual

Does anyone out there have one, or know where I can get one? Mine has developed a horrible buzz and crackling sound (likely a bad capacitor or two) but I’d like to have a look at the schematic to help narrow down where to look, as this thing has what appears to be a couple hundred little caps in it.

they have that manual which is the same as roland sc33, but they want $14.95.

i would first check your power supply first. also you could have cold solder joint, so the best think for that is to resolder the board. use a low wattage soldering iron and good rosin core solder or just rosin flux which comes in paste or liquid. there are acid fluxes as well but they need thorough rinsing in distilled water.

Thanks! I might trying resoldering the board first. Then, if that doesn’t help I might spring for the $14.95

What are you using for a power supply on this?

I was looking at a Korg SAS-20 with a horrible humming noise. Turned out to be the universal power supply I was using.

Also, check the output of any voltage regulators used. Noise in the power supply will impact the rest of the circuit.

It’s the original power supply (wall wart) that came with the unit. Interestingly, the noise it not consistent. That’s what lead me to suspect it’s a cap or something similar. Flexing the case will actually change the level of noise.

Oh, that sounds interesting… I think you’ve got a bad connection or two.

Open the case and power it up, then tap on components. That might help you narrow it down some. Focus on stressed parts like connectors, and then on electrolytic caps that might come in contact with the case.

Over time, the connections to a jack will get stressed from the weight of cables plugged into it, and the solder connections will break down. Not uncommon to find the ground side of an output jack will come loose, and you will get a lot of humming noise.

bad solder joint - or bad cable connection. if you put pressure on the circuit board and it does that then its a bad solder joint.

So, I spent over an hour going over the board, resoldering any suspect looking joints (there weren’t many). No change. One thing I DID discovery is with the jack board removed from the unit, but still connected, my issue is reduced to an annoying hum, most likely the usual 60 Hz from the line. When I put it back in the case and screwed it in place, that added some crackling to the hum. Very frustrating.

Noise problems are always frustrating.

That hum is interesting. 60Hz implies a ground loop. And you definitely have an issue with the cabinet

It’s odd, since the entire case is plastic.

That’s fine. A metal cabinet could have provided some grounding and some RF shielding, but plastic is well enough for enclosing it.

I’m wondering if that case is somehow twisting the board a bit. Might loosen the screws and see if the noise persists. You might even be dealing with a broken trace.

I’ll have to take another look. I didn’t see anything obvious, but it may not be obvious. Maybe I need better glasses too. LOL

Glasses might not help LOL. I used 3x reading glasses but still couldn’t see a break on my Proteus 1. Even once I’d found the break I couldn’t see it. But it made a difference when the board was flexed.