SEX 3.0 - Amp itself is buzzing (not through speakers/headphones)

yay · 1780

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Offline yay

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Hello, i'm building my SEX 3.0 kit at the moment, and just did the glow test.
I noticed a buzzing coming from the amp during the test, but everything lit up perfectly.
Is that normal? Don't think i had a similiar noise from my crack while building, or after



Offline Doc B.

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Tighten your power transformer mounting screws.

Dan "Doc B." Schmalle
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Offline yay

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tightneed them again, but that didn't seem the issued. tightened all screws very well



Offline Doc B.

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How loud is this hum? Really loud or just something that you happened to notice? If loud, you might need to correct something. If very subtle, it might just be normal.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline yay

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I wouldn't call it subtle, as far as i can tell it i mounted all the parts correctly, too.
I took some pics of the wiring, if those help
OT wiring looks weird on the pics, but it is correct (for 8 ohm, i wired it for 4 ohm first and re-wired after i noticed)
http://imgur.com/a/jqLBn

edit: the drain wire from the shielded cable going to H1U is not soldered (it doesn't seem to say to solder it, just attach, i just checked again), but in later pictures it appears to be soldered.
Could that be the problem?

edit2: it wasn't
« Last Edit: May 03, 2017, 08:28:24 AM by yay »



Offline Paul Birkeland

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It looks like something strange is sticking up from A12.  What is that?  Something odd is also sticking up from B12.

H6L needs a bit more solder/heat.

I agree regarding the transformer screws.  They need to be very, very tight.


Paul "PB" Birkeland

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Offline yay

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that's just unclipped lead, i clipped them after the photos.
will try to tighten them even further, but i doubt i can get them much tighter.
will get back to you in a few minutes after trying those

edit: put some extra solder on H6L, and REALLY tightened the screws again. I can't tightem them anymore by hand without breaking the screwhead, one already clipped a bit and is now hard to unscrew or screw further if i have to.
I only painted the top layer of the bell top on the transformer, but after screwing them really tight the screws should be definitely thought the layer of paint, i see it chipping at the edges of the screws.
no changes, sadly

i can try and take some more detailed pictures in the daylight?
« Last Edit: May 03, 2017, 09:55:24 AM by yay »



Offline Doc B.

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Unless there is something pulling excess current, which would be evident in voltage measurement, there isn't much to go on for a cause. It's a possiblity that when the amp is complete the AC voltage in the power transformer high voltage secondary will be pulled down enough by the amp circuit to make it more quiet. I would complete the assembly and revisit the issue if it's still there when you are done.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline yay

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voltage measurements were spot on (+2-3%), and wired it for 225-235 (had 229).

i will just continue with it then, let's hope it quiets down enough or fully.  ;D



Offline yay

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finished it, all measurements on point and sound very nice with my hd800 and orca, dead silent.

the buzz is still there tho, but not as loud. still a bit annoying
« Last Edit: May 04, 2017, 04:58:33 AM by yay »