Occasional crackling and static noise... [resolved]

[Wplchou]

Hi, I have been using the Crack + SB upgrade for a couple of mths and been working fine till this morning, theres a bit of crackling and static noise which comes on and off... It can be the case that it doesnt come on for an hour and works perfectly and black backkground, and then occasionally it comes again... I notice the noise doesnt get louder or quieter with volume, as in volume can be turned off, and the crackling noise is same. I have tried to poke a few of the wires with chopstick and cant really reproduce the crackling... any ideas what can do to fix it please?

[Paul Birkeland]

It's either this:
https://forum.bottlehead.com/index.php?topic=11676.0

or a cold solder joint in your amp.

[Wplchou]

Thanks Paul,

So I took the Crack out from my study to the Operation room (my living room table Where I have a different Power cable and source (DAP instead of computer). The noise is not there, so i suspect its to do with the computer noise or the IEC cable i have in the study. So I wanna give the method in the post you attached a go. Just to clarify, https://www.digikey.com/en/products/detail/stmicroelectronics/STTH2R06/691922 , this diode I would need 2 of them, and the buss wire connected Terminal 16 to ground lug to IEC Earth. So i Remove the part between the Ground lug to the IEC earth and replace with the 2 diodes twisted together and in opposite polarity ... umm just as I finish typing this post tiny bit of crackling comes back, oops and gone... if I were to have a cold joint is there a way to locate the problem?

[Paul Birkeland]

Yes, correct with those diodes. 

On something with so few solder joints like a Crack, I don't spend any time looking for which joint is causing the issue, I just reheat all of them other than the sensitive ones (the power switch and where the LEDs connect to the pins on the 9 pin socket).

[Wplchou]

I just use chop sticks and poked around again and i have located the problem. the long black wire connecting ground 12 and headphone jack was crackling when i poke it. I just reheated the joint and added a little bit of solder, seems like problem is gone! on this note can I ask when you mean "reflow" I see on the internet I need to use flux? is that necessary? I dont have flux around but seems like just reheating and the old solder melts and flowed thru the terminal and left with the desirable shiny finish... and amp works. But I just wanna know whats the proper way to "reflow" so to speak?

[Deluk]

The solder you used contains its own flux as an internal core. A bit of manufacturing magic. Using a flux pen does allow you just to re heat the joint and use the existing solder. That's good when the joint already has adequate or too much solder. Also saves you sucking off the solder and starting over.

[Doc B.]

The proper way is to reheat until the solder flows enough to create a fillet in the joint. You can add just a touch of extra solder if the problem was created by not enough solder in the original joint.

[Wplchou]

Thanks a lot for the help