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Post subject: DRRI REVERB HUM
Posted: Mon Feb 12, 2018 5:24 pm
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My deluxe reverb has developed a very noticeable hum :? That gets louder as the knob is turned up and down when the knob is turned down. Anyone have an idea what is causing this?

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Post subject: Re: DRRI REVERB HUM
Posted: Mon Feb 12, 2018 8:02 pm
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Maybe a preamp tube. If you know the tube location(s) that deal with reverb, swap out similar tubes and see if that corrects it. If so, replace the tube.


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Post subject: Re: DRRI REVERB HUM
Posted: Tue Feb 13, 2018 2:48 am
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Sorry I did not read REVERB about the hum :oops:


Last edited by stratele52 on Tue Feb 13, 2018 1:57 pm, edited 1 time in total.

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Post subject: Re: DRRI REVERB HUM
Posted: Tue Feb 13, 2018 3:35 am
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If the hum is only associated with the reverb, I would suspect the tubes in the reverb circuit.

The V3 12AT7 is the reverb driver. That's the hardest working preamp tube and the one most likely to have gone bad.

V4 12AX7 is the reverb recovery and a gain stage. It's a possibility too.


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Post subject: Re: DRRI REVERB HUM
Posted: Tue Feb 13, 2018 7:25 am
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Does the hum happen on both channels? Which "knob" are you turning, on which channel? :?:

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Post subject: Re: DRRI REVERB HUM
Posted: Tue Feb 13, 2018 1:45 pm
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Yes, we're all chasing our tails a bit.

I assumed from the title ("DRRI Reverb Hum") that it's the reverb that's humming, and that the knob he's turning is the reverb knob.

If so, it dawns on me to ask for a description of the "hum". Sometimes if the tank shifts inside the bag, you can get various types of feedback when you turn up the reverb knob. Sometimes it's a traditional squeal, but othertimes it's a low-pitch that's kind of hum-ish.

(Do DRRI's have the tank inside a bag like the original DR's? I assume so but I've never actually looked inside a DRRI.)


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Post subject: Re: DRRI REVERB HUM
Posted: Tue Feb 13, 2018 1:59 pm
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Reverb cable, bad ground ; at cable sides or RCA plugs on amp or on reverb tank


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Post subject: Re: DRRI REVERB HUM
Posted: Tue Feb 13, 2018 4:38 pm
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Thanks so much folks, there's a lot of good info here. after I have tried these suggestions, I will revisit this thread. This is a low hum that seems only affected by the reverb knob, Reverb knob acts like a volume knob for the hum.

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Thanks so much..........Ron
2014 am spec tele
2015 am spec strat
2007 deluxe strat hss
2016 mag7 tele
2016 Am Elite Strat
2016 gretsch 5622
2017 gretsch 6137
2018 gretsch 6120t


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Post subject: Re: DRRI REVERB HUM
Posted: Tue Feb 13, 2018 4:54 pm
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oldgretschguy wrote:
Thanks so much folks, there's a lot of good info here. after I have tried these suggestions, I will revisit this thread. This is a low hum that seems only affected by the reverb knob, Reverb knob acts like a volume knob for the hum.


Folow our advices;

Check reverb tubes, check reverb cable jack and plug


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Post subject: Re: DRRI REVERB HUM
Posted: Fri Feb 23, 2018 11:30 am
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Thanks to the forum advice I removed V3 and V4 and they appeared to be ok. I loosened and tightened the reverb cables and after doing these steps the hum is gone. What a great resource this forum is.

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Thanks so much..........Ron
2014 am spec tele
2015 am spec strat
2007 deluxe strat hss
2016 mag7 tele
2016 Am Elite Strat
2016 gretsch 5622
2017 gretsch 6137
2018 gretsch 6120t


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Post subject: Re: DRRI REVERB HUM
Posted: Fri Feb 23, 2018 1:40 pm
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Plug and unplug few time reverb cable to clean contact for long time.
Best is to use electronic contact cleaner.
Do same on tubes pins.

May I ask you what do you do to say V3, V4 appeared OK ?


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Post subject: Re: DRRI REVERB HUM
Posted: Fri Feb 23, 2018 7:21 pm
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oldgretschguy wrote:
Thanks to the forum advice I removed V3 and V4 and they appeared to be ok. I loosened and tightened the reverb cables and after doing these steps the hum is gone. What a great resource this forum is.
I'm glad that's worked out for you. Always good to hear good news. If you're still following this thread, I just wanted mention that you can't tell a tube is OK by looking at it. Every bad tube I've had looked OK, but they weren't OK. The amp techs here can tell you how to check them, but I know if swapping out the tube in question with a known good one solves the problem, then I had a bad tube. Even then, I'm not sure if that's definitive.


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Post subject: Re: DRRI REVERB HUM
Posted: Sat Feb 24, 2018 2:15 am
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LawFlow wrote:
oldgretschguy wrote:
Thanks to the forum advice I removed V3 and V4 and they appeared to be ok. I loosened and tightened the reverb cables and after doing these steps the hum is gone. What a great resource this forum is.
I'm glad that's worked out for you. Always good to hear good news. If you're still following this thread, I just wanted mention that you can't tell a tube is OK by looking at it. Every bad tube I've had looked OK, but they weren't OK. The amp techs here can tell you how to check them, but I know if swapping out the tube in question with a known good one solves the problem, then I had a bad tube. Even then, I'm not sure if that's definitive.



+1000

And tube tester can't test noisy tubes and they can't test many of the tubes issues :(


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Post subject: Re: DRRI REVERB HUM
Posted: Sat Feb 24, 2018 5:10 am
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Nitpicking: most often a bad tube looks perfectly fine, but there is one type of failure that can be visually diagnosed.

If the silvery coating inside the tube ("getter flash") has turned white, the tube is stone cold dead. It's lost its vacuum, either leaking around one of the pins or a small crack in the glass.

It's difficult/impossible to create a strong enough vacuum for a tube to function properly. They suck out as much air as they can but there's always a little left. So they fill the getter with a mercury compound that absorbs/reacts with air. Then they heat the getter so that the compound boils and sprays out of the getter cup, coating part of the glass. It then absorbs the remaining traces of air.

If a leak develops, all the getter flash reacts. When it turns white, that's a clear-cut visual sign that the tube has too much air inside to function.


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Post subject: Re: DRRI REVERB HUM
Posted: Fri Dec 13, 2019 6:07 pm
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I just fixed my problem. I just opened my brand new Custom 68 Deluxe Reverb and there was a loud "pop" when taking it out of standby. When I turned up the reverb, the loud hum became louder and would drown out the guitar.
I had a small flashlight shining in the compartment, while looking for the problem. When the beam landed on one of the 12ax7 tube, I could hear the light hit the tube. It was shrouded in the aluminum housing, but I could hear the light hitting the tube because the pitch of the hum changed. When I put the light closer, the hum got louder. I changed out that tube and the amp was completely silent. From switching from standby to cranking the reverb to nothing being played. There wasn't even a small crackle in the silence. Best thing ever. Thanks forum.
You may want to try the beam of light test instead of the chopstick tap test the next time you check your tubes.


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