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Post subject: Help! Amp has hum
Posted: Tue Feb 09, 2010 2:54 pm
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Hi,

My Blues Deluxe has a hum. I replaced my power tubes (the hum was there before). Could this be the preamp tubes or something else altogether (like filters etc). It is weird, that even with amp volume and gain at zero, at any channel, there is still this hum. This amp used to be quiet so I know it isn't normal.

Any help is much appreciated! Thanks in advance!


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Posted: Tue Feb 09, 2010 4:28 pm
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Is your amp near any computer monitors, cell phones, florescent lights?
Have you tried it in a different room and different circuit in the house?


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Posted: Tue Feb 09, 2010 7:55 pm
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Galore is this the same amp that your tech put the 80uf filter cap in? If so, it might need a full recap job. Art

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Posted: Wed Feb 10, 2010 6:05 am
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Hi Art,

You were right, it was a filter though not the 80u, it was another one (an original). I had the same tech confirm and fix the problem. Now, I have two 450v 80u and 5 remaining 350v 100u. He told me that this should still be ok. The amp is now dead quiet. So since the 350v 100u caps are not available locally, I do plan to import a whole set of filters soon to update all of them as they seem to be failing one by one.

I went to Amazon and found this: 100uF 350V Radial Mini Electrolytic Capacitor by Xicon

http://www.amazon.com/100uF-350V-Radial ... =8-1-fkmr1

Would this be a good replacement? Any suggestions as where to get a good replacement online? I guess my worry is that it does get pretty hot with the tubes and all in there and wonder if there are other caps that may be better suited for the tube environment.

Thanks also 63 supro for replying right away.

Much appreciated :)


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Posted: Wed Feb 10, 2010 9:23 am
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Double check whether you need a radial or an axial cap. No difference other than the leads are at each end in an axial cap while the radial has both leads at the same end. I'd think for amps you'd want axial.

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Posted: Wed Feb 10, 2010 4:24 pm
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Yeah Galore, that's what I was implying. All the caps are probably due for replacement. Antique Electronic Supply www.tubesandmore.com is a good source of amp parts. I prefer the Sprague Atom electrolytics, but you might want to have your tech check the demensions to make sure they will fit in the amp, before you purchase. Your amp uses axial filter caps. That hum could also be a bad tube. Art

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Posted: Wed Feb 10, 2010 6:06 pm
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Thanks guys for the input. The hum is gone now since we changed one of the caps, the tubes are new, JJ 6L6GC. I noticed before changing that there was a hum already to begin with but it was very soft (with the Sovteks). The Sovteks were microphonic and sounded brittle so I changed the tubes. Putting the JJ's on, it seemed to amplify the problems. The good thing I think is that the tech told me, we found out that one of the capacitors was broken. The other is that he also told me that my preamp tubes are microphonic and noisy during the gain stage. On the clean it is not so bad, hardly noticeable but still there is a very slight hiss.

I will defintiely be changing all the axial filters caps and preamp tubes in a few days.

Thanks again!:)


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