Left channel noise on Crack w/ Speedball

[Nayr]

Hi,

I'm having a couple issues that are resulting in left channel noise, it alternates between a light scratchy crackling sound and semi high pitched electric buzzing.

• The noise still occurs when the amp is disconnected from a source with the volume turned down, and it is intermittent.
• Changing the tubes changes the sound profiles a little but the issue persists.
• Sometimes when the electric buzz is happening flicking/wiggling the power tube makes it stop for a split second.
• The noise seems harder to reproduce when it is on it's side or upside down... ??
• Prodding at the joints and cables with a chopstick hasn't told me where the issue may be. I think I prodded against some of the connections so much that I caused new issues that I had to then fix.

I've done a lot of wicking solder away and then resoldering, I put particular effort into:

• The octal socket
• Both Speedball PCBs
• The connections to the PCBs (replaced most wiring with the wire from the Crack kit instead of the thinner Speedball wire as I didn't have the right tool to strip it properly.)
• The black wires in the corner of the headphone jack
• The RCA jacks

I've also carefully tired to redo the connections on the 9 pin socket but was a bit worried about overheating and cooking the LEDs.

One area that I have not properly wicked and resoldered is the area around the 270Ω 5W wirewound resistor and the 270KΩ 1W resistor (13L), I can't really reach it properly and the leads for the stuff around there are pretty short.

Could I get some help narrowing down where the issue is? Or at least pointed towards all the left channel things.

I can provide pictures and voltages and stuff, but I thought that this post was already too long; I'll wait for confirmation of what would be most useful first.

Cheers,
Ryan

[Paul Birkeland]

If the issue goes away with the amp upside down, that tends to suggest a loose connection on one of the sockets.  Just in case, you could also perform this mod in case you have a very noisy powerline.

https://forum.bottlehead.com/index.php?topic=11676.0

[Nayr]

I ended up redoing both sockets today, sadly still having issues.

It might actually be interference from my PC, which is a bit odd as I didn't have any issues before and didn't change anything, and I thought the scratchy sound was a bit different to what interference normally sounded like. I did notice today that for a little while there was a bit of buzzing in the right channel too though.

I'll try the mod when the parts eventually arrive, I'll probably order them tomorrow; it's apparently hard to get that part in Australia.

[Paul Birkeland]

This would also work just fine:
https://www.digikey.com.au/product-detail/en/comchip-technology/1N5401-G/641-1314-1-ND/1979679

[Nayr]

I was looking at Digikey but I think that they ship from the US as well.

I ended up buying the diodes that the other guy suggested from Jaycar because it is nearby (his now deleted post referenced the 1N5408 3A 1000V). Would that particular one work? I installed them* earlier today but the noise is still there.

Also, does this mod help at all with noise from WiFi routers?

* Edited for clarity.

[grufti]

You say "it" when you refer to the diode. Do you mean one diode [it] or two? I would use "them" to talk about two diodes and you need two installed in opposite directions for the noise suppression to work. Your 1N5408 should work just fine.

[Nayr]

I mean two, I bought two of them and installed them per the post PB provided earlier.