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Post by ss "Shane" on Oct 23, 2015 9:24:27 GMT -7
I'm sure by now somebody will get tired of answering my questions, but why I have the ears of Z people who know I'll throw this at y'all.
When I crank to the volume level of a fairly strong drummer I get a physical buzz from my Therapy. It's not at all loud enough to be heard in the mix because it doesn't come out of the speakers. Just from the head. I can tell that it coming from somewhere in the neighborhood of the 6L6's side. I don't wanna turn my low end down and I know its the 2X12 cab causing it ....at least I think.
Here are some facts that might help with a diagnosis: 1. I put dish rags under the rubber amp feet and it goes away 2. I place the amp head in the floor and it goes away 3. Only really occurs when the tubes get nice and hot 4. I noticed the amp sits just a hair off balance when on the cab, kind of like when you have to put paper under one leg of the kitchen chair to level it out.
I know some will recommend to keep the rags under the cab or something but really, I don't wanna tote rags everywhere I go. That's just something else I'll have to remember and probably forget. To be honest I would have no problem with this issue but I believe in time it will rattle a component loose. This is my second new Z amp head and I've never had this problem with the other one. Any suggestions? Thanks again!!
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Post by premiumplus (Dave) on Oct 23, 2015 15:44:00 GMT -7
The sound is coming from the head itself, and not from the speakers? You've probably already tried this, but... If so, check to be sure that all the head bolts are tight, look for anything that might be loose and rattle. If it's coming out of the speakers, it sounds like you may have a microphonic tube.
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Post by ss "Shane" on Oct 23, 2015 16:02:41 GMT -7
Yes it's coming from the head and not the speakers. One thing I did do was switch the rubber feet around and now the head sits level on the cab. This decreased the buzz by a little bit but it's still there. It sounds like possibly the aluminum looking sheet of metal that the components are mounted to (not good with amp parts terminology). If it's not that then it may be the chrome retention mounts for the tubes.
I've tightened the screws on the exterior of the head but was kind of scared to go jacking with the small screws on the inside. Not many to tighten by just looking at it though. I've seen posts about tightening the bottom of the chassis but have no clue how to do that.
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Post by Maddog on Oct 23, 2015 16:12:42 GMT -7
I've had rectifier tubes buzz like that .... Maybe sub in a fresh one....
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Post by ss "Shane" on Oct 23, 2015 17:33:00 GMT -7
I've had rectifier tubes buzz like that .... Maybe sub in a fresh one.... The rectifier tube is notocibaly brighter than the others. Not sure if that's a good thing or not. The sounds seems to be coming from that facinity
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Post by simpleton on Oct 23, 2015 19:55:08 GMT -7
Sometimes the insides of the tube are what is rattling. I've had it happen with a Rectifier too. Playing quiet enough to hear rattles has literally driven me crazy. Now that I am officially crazy it doesn't bother me....well compared to the voices. I kid, I kid...but I have had tubes rattle.
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Post by premiumplus (Dave) on Oct 24, 2015 3:23:41 GMT -7
I agree with all above. I've had tube innards rattle too. There are also a couple of hole plugs in the chassis that are an outside possibility. As is the screen on the back panel. Don't know how much experience you have with electronics...You have to pull the chassis out of the cabinet to check for loose hardware inside the amplifier (the 4 large phillips #3 bolts on the bottom). If you do that, just be sure that when you power down the amp you leave the standby switch on. This will (mostly) discharge the power supply capacitors that can hold hundreds of volts. Make sure you don't touch any wires inside the amp. And obviously, unplug the amp when you're working on it. Use common sense; I hope you find it, rattles drive me nuts. Nutsier. Nutsiest. Cccrazy.
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Post by southmusic70 on Oct 24, 2015 5:47:56 GMT -7
There is a photograph from a Beatles concert at Carnegie Hall in which both Lennon and Harrison's amp heads are on the floor next to their speaker cabinets, so if you try this (and have room for it on the bandstand) and anybody ridicules you, show them the photo.
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Post by benttop (Steve) on Oct 24, 2015 8:06:49 GMT -7
How far away from the wall is your cab? You could be getting a reflected sound pressure issue that I've seen here numerous times. Pull the cab out a foot and see what happens.
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Post by ss "Shane" on Oct 24, 2015 12:15:05 GMT -7
I keep the amp more than a foot off the wall. I'm really hoping this is an easy fix, sending an amp back is so inconvenient. I pulled the 5AR4 out and when I shook it I could hear just a hint of something shaking around in there. It's really faint and barely noticable. I had to mute the TV and the wife to even hear it.
Removing the chassis as nothing I would do on my own or without a telephone walk-through but maybe doing that is where the fix is. So far this issue is the only thing keeping it from being absolutely perfect in every way.
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Post by benttop (Steve) on Oct 24, 2015 18:21:36 GMT -7
I keep the amp more than a foot off the wall. I'm really hoping this is an easy fix, sending an amp back is so inconvenient. I pulled the 5AR4 out and when I shook it I could hear just a hint of something shaking around in there. It's really faint and barely noticable. I had to mute the TV and the wife to even hear it. Removing the chassis as nothing I would do on my own or without a telephone walk-through but maybe doing that is where the fix is. So far this issue is the only thing keeping it from being absolutely perfect in every way. Well good luck with your investigation. Rattles can sometimes be difficult to locate...
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Post by heynewguy (Ol’ Bill) on Oct 24, 2015 18:43:20 GMT -7
I had to mute the TV and the wife to even hear it. I would not recommend muting the wife to any man!
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Post by southmusic70 on Oct 24, 2015 19:35:09 GMT -7
I didn't even know it was possible to mute your wife.
Probably not a good idea, though,
Pure fantasy, actually.
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Post by ss "Shane" on Oct 24, 2015 20:14:44 GMT -7
Ok I think I took care of it...I'm far from an amp tech so go easy on me lol. I took the back screen off and sat down with my guitar while hitting the low e string and letting it ring out. At the same time I put my fingers everywhere a vibration could be. The biggest box that sits behind the 5AR4 tube (no clue what this box is called lol) was the culprit. Actually it was the mounting screw and washer. When I pressed down on it the buzzing stopped. So I found the shortest screwdriver I could and tightened it down a bit more. I really need a 90 degree angled screwdriver to do it better but for now it fixed it!
Hopefully a reader with the same issue will benefit from reading this. And oh, I sure as heck would like to know what that black box is haha!
PS...the wife is un-muted now! She says hi and for y'all to stop causing me to spend money lol
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Post by fishbeiner on Oct 25, 2015 0:09:08 GMT -7
And oh, I sure as heck would like to know what that black box is haha! PS...the wife is un-muted now! She says hi and for y'all to stop causing me to spend money lol Shane, I believe that would be your power transformer. Glad you resolved your issue with the Therapy. Hope you are able to enjoy it 100% now! It really is an awesome amp.
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Post by sharkboy on Oct 25, 2015 5:23:32 GMT -7
I have never tried to mute my spouse, as I am averse to red plating.
Glad it worked out. Quite often, you can diagnose fairly easily with the frequency of the vibration. Even if the rattle goes away, it might be worthwhile to look into improved mechanical decoupling of the speakers and the amp. Probably, the leading cause of tube failure is mechanical shock (but some of that is from handling/transport.)
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Post by benttop (Steve) on Oct 25, 2015 6:07:52 GMT -7
Ok I think I took care of it...I'm far from an amp tech so go easy on me lol. I took the back screen off and sat down with my guitar while hitting the low e string and letting it ring out. At the same time I put my fingers everywhere a vibration could be. The biggest box that sits behind the 5AR4 tube (no clue what this box is called lol) was the culprit. Actually it was the mounting screw and washer. When I pressed down on it the buzzing stopped. So I found the shortest screwdriver I could and tightened it down a bit more. I really need a 90 degree angled screwdriver to do it better but for now it fixed it! Hopefully a reader with the same issue will benefit from reading this. And oh, I sure as heck would like to know what that black box is haha! PS...the wife is un-muted now! She says hi and for y'all to stop causing me to spend money lol If you don't want to spend money, you are hangin in the wrong place!
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Post by fishman on Oct 28, 2015 21:15:02 GMT -7
I don;t know about anyone else's amp, but the tube holders on mine are like vise grips. When I swapped V1 and tried some 6V6's in, it was a chore to get the tubes out. These holders hold like none other I have seen. The tubes don;t move...period. Some of my old fenders have good tube holders, but nothing with the "bear trap" grip these babies have.
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