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Jan 22nd, 2018, 4:01pm



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BritNoob
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xx Re: Lucky 13 transformer buzz/hum
« Thread started on: Apr 9th, 2011, 11:25am »

My Avenger is the most noise free high gain amp ive ever played. But it has DC heat on the first 2 preamp valves which helps. I doubt the lucky 13 has that.

I guess you mean 50hz hum coming through the amp, and not hum coming from the mains transformer itself.

I imagine with the master volume at zero you should get no mains hum through the speakers. But you might hear mechanical hum from the transformer. You can get 50hz hum and 100hz hum a number of ways. 100hz is caused by rectification of AC voltage to DC after the mains transformer and bad filtering or a few other things.

bad hum can also be bad tubes.
does the level of the hum increase as you turn the MV louder or does it stay the same?

where in the UK are you based?
« Last Edit: Apr 9th, 2011, 11:27am by BritNoob » User IP Logged

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cak900
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xx Re: Lucky 13 transformer buzz/hum
« Reply #1 on: Apr 9th, 2011, 3:44pm »

Doh, I went to edit the original post and deleted it instead. No the buzz is there with the volume turned right down and no guitar connected. Is reduced on the clean channel when the reverb is turned down but is bad on the Overdrive channel whether the reverb is on or off.
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BritNoob
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xx Re: Lucky 13 transformer buzz/hum
« Reply #2 on: Apr 9th, 2011, 4:24pm »

Does the turning the master volume effect the noise level when no guitar is plugged in?

If not then my guess would be the noise is coming from after the MV dial.

Another thing you can try is pulling out PREAMP valves starting with V1 and working along (V2, V3, V4) etc.

You might find pulling V1 makes no difference, or that pulling each valve in turn slowly decreases the noise. You probably won't get any noise with the Phase Inverter valve pulled since the power stage usually rejects noise pretty well in a push/pull amp.

You might find a bad valve, or you could narrow the noise down to coming from the preamp or power amp stages.

If you do that remember to pull each valve out starting with V1, always turning the amp OFF before you remove one, and letting it cool.
DO NOT remove any of the power valves and switch the amp on.

If you're not confident, then don't try it.

I had 100hz and 50hz hum in an amp once and narrowed it down to a bad filter cap. which I replaced. that helped a great deal. then I converted the amp to star grounding and adding DC elevated filament heaters. But that was in a turret built amp, not a PCB.

if you're near london. Frank @ JPF Amps in angel music (above macaris) on Denmark Street is a GREAT tech.
« Last Edit: Apr 9th, 2011, 4:26pm by BritNoob » User IP Logged

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luckythirteen
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xx Re: Lucky 13 transformer buzz/hum
« Reply #3 on: Dec 15th, 2014, 7:44pm »

I had the same problem and my tech discovered that the pcb was conductive and sending current to V1. Not sure how he fixed it, but she is quiet now.
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Billielvis
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xx Re: Lucky 13 transformer buzz/hum
« Reply #4 on: Jan 28th, 2015, 1:25pm »

Hi there, any info as to how your tech fixed this? I have exactly the same problem on a lucky 13 that I bought recently with a very early serial number, I am UK based too, South west. Cheers
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