Hey all.
Been a while since I've been here, but always nice to come back 🙂
A few years ago I built an F3 amplifier, and it works beautifully. However, for the past year or so, there's been a crackling sound in the right channel.
I've attached a link to a recording (it's not a great recording, it seems to be an octave higher than what it actually sounds like).
If I were to describe it, it'll be like an untuned AM receiver (as in, not white noise).
Any suggestions for diagnosis ? The other channel is fine 🙂
Click here for audio
Been a while since I've been here, but always nice to come back 🙂
A few years ago I built an F3 amplifier, and it works beautifully. However, for the past year or so, there's been a crackling sound in the right channel.
I've attached a link to a recording (it's not a great recording, it seems to be an octave higher than what it actually sounds like).
If I were to describe it, it'll be like an untuned AM receiver (as in, not white noise).
Any suggestions for diagnosis ? The other channel is fine 🙂
Click here for audio
recheck all solder joints
tripple check power resistors , whenever they are - in power supply or on amp pcb
if that doesn't help, start replacing (one by one) semiconductors , going from output to input
tripple check power resistors , whenever they are - in power supply or on amp pcb
if that doesn't help, start replacing (one by one) semiconductors , going from output to input
sounds like a changing DC offset due to a broken connection.
Similar to a scratchy vol pot.
As Zen says check all connector/soldered joints first.
Try tapping components/wires/connectors with a pencil.
Similar to a scratchy vol pot.
As Zen says check all connector/soldered joints first.
Try tapping components/wires/connectors with a pencil.
I'll give all those suggestions a try.
I do recall once that I swapped the left and right PSU (dual mono), and it remained in the right channel, so I did rule out the PSU early on. Might swap them around again to verify that though.
I do recall once that I swapped the left and right PSU (dual mono), and it remained in the right channel, so I did rule out the PSU early on. Might swap them around again to verify that though.
Quick question about the pencil test - is there anything I should be listening for ?
The noise is intermittent, so I can't really test for it dissapearing while flicking bits with the pencil ...
The noise is intermittent, so I can't really test for it dissapearing while flicking bits with the pencil ...
I always called this the chopstick test.. because I use a chopstick. The crackling may be intermittent, but I think the point here is to exacerbate the problem.. a loose connection or wonky part.. before you start unsoldering/replacing things. Might want to tug or change the angle of various input and output wiring to the pcbs while you're at it to see if that makes any difference. I had a bad connection like that one time..
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So - seems to be resolved 😀 😀
Using the pencil, it seemed like C2 (the cap to ground) was the culprit. Tapping it make a scraping sound in the right channel - very similar to the crackling sound I would get.
I took the board out (really annoying - had to remove the heatsink, then un-screw the transistors, unsolder the speaker terminal wires), and resoldered the capacitor, as well as the items in its path and physical vicinity.
That seemed to do the trick.
Hopefully that's the last of it. The amp weighs a butt load - moving it, disassembling and re-assembling it is a major PITA. I love it though 🙂
Using the pencil, it seemed like C2 (the cap to ground) was the culprit. Tapping it make a scraping sound in the right channel - very similar to the crackling sound I would get.
I took the board out (really annoying - had to remove the heatsink, then un-screw the transistors, unsolder the speaker terminal wires), and resoldered the capacitor, as well as the items in its path and physical vicinity.
That seemed to do the trick.
Hopefully that's the last of it. The amp weighs a butt load - moving it, disassembling and re-assembling it is a major PITA. I love it though 🙂
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