June 20, 2017 at 4:04 am #2086
I finished putting my Macchiato together. When I switched it on the first few seconds it seemed to work fine but then a very loud rattling sound comes out of the speaker from the moment I switch it on. The sounds is constant and only changes a tiny bit when the volume knob is fully to the left. No synth sounds in the background… You have any experience which part might cause this trouble?
StanJune 20, 2017 at 10:21 am #2088
I’m sorry to hear you are having trouble. I have never heard of that particular issue before. Do you hear anything through your headphones when you plug them in to the output jack (keep the volume low when testing this)? Let me know what you find out.
-BrachJune 23, 2017 at 7:21 am #2095
It makes the same very loud rattling sound with the headphones…
StanJune 23, 2017 at 8:27 am #2096
That is very peculiar. I’ve never heard a sound that could be described as a rattle coming through the headphone jack. Does it sound more like a mechanical rattling noise or an electrical oscillation? An oscillation could sound like anything from a
“thump thump” to a high pitched whine.
Since the sound is coming from the headphone jack, I’m suspecting the circuit around the LM386 audio amplifier chip could be the issue. Please double check (and even re-solder) the pads in the audio path…R14-16, R19-20, R22, C8-11, C13, C3-4, U3, and of course make sure the speaker and the headphone jack are properly soldered.
-BrachJuly 1, 2017 at 12:52 pm #2109
I checked the connections. I’m still a rookie in soldering but it looks fine to me. The sound that it makes is very loud and I think its more a mechanical sound but I’m not sure we mean the same thing haha. Headphones or speaker gives the same result, 9V battery or adaptor input makes also no difference…
StanJuly 3, 2017 at 9:50 am #2115
Even if the solder joints on those parts i mentioned in my previous post look fine, resolder them anyway. Don’t add anymore solder just heat them up until they flow onto the pad. We call it “reflowing” the solder joints. Sometimes it’s easier to reflow all of them than try to trace out the single bad joint. Also make sure that all of those components are in the correct place and nothing is switched. Since you said the volume control has no effect on the sound then it must be in the signal path after pot VR9. Look very closely at all the solder joints around the audio amp ic U3, make sure nothing is bridged…use a magnifying glass if you need to. Good luck. Let me know what you find.