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Post subject: Re: My Modded Champion 600
Posted: Mon Oct 31, 2011 8:34 pm
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I've got what appears to be very bad tube rattle now in the 6V6S. On certain note it buzzes like crazy. If I squeeze the tube with my fingers, it seems t lessen. If I rap on the cabinet, it makes crackling noises. I put the stock Chinese tube back in and it does the same thing. But when I pulled the chassis out of the cabinet and set it to the side and played through it, it doesn't seem to buzz/rattle. I looked at all the solder joints and everything looks OK. A new tube and vibration damping ring are on their way. Anyone have any other ideas about what this problem could be caused by?

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Post subject: Re: My Modded Champion 600
Posted: Mon Oct 31, 2011 8:49 pm
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Is the tube socket itself securely fastened to the chassis?

Arjay

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Post subject: Re: My Modded Champion 600
Posted: Mon Oct 31, 2011 9:22 pm
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You're on the right track Retroverbial

It is likely the side chassis screws need to be tightened. I found that if those screws aren't really tight you'll get that noise. You can push up on the center of the chassis, beside the output tube socket, and see if that noise goes away. The chassis screws in the rear mount to wood, so those can't be tightened very much, but the side screws go into the chassis. :idea:

Edit:
I presumed that the tube retainer is tight to the tube base and not rattling.

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Post subject: Re: My Modded Champion 600
Posted: Mon Oct 31, 2011 9:27 pm
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Retroverbial wrote:
Is the tube socket itself securely fastened to the chassis?

Arjay


Yep. Double checked both tube sockets as well as the PCB mounting screws and transformer screws. I loosend each screw and then retightened it since that sometimes will relieve stress in the surrounding sheet metal. It made no difference.

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Post subject: Re: My Modded Champion 600
Posted: Mon Oct 31, 2011 9:37 pm
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shimmilou wrote:
You're on the right track Retroverbial

It is likely the side chassis screws need to be tightened. I found that if those screws aren't really tight you'll get that noise. You can push up on the center of the chassis, beside the output tube socket, and see if that noise goes away. The chassis screws in the rear mount to wood, so those can't be tightened very much, but the side screws go into the chassis. :idea:

Edit:
I presumed that the tube retainer is tight to the tube base and not rattling.


Yep. The side chassis mounting screws are tight, as is the tube retainer.

One of the other things I did was changing the position of the chassis in the cabinet. Since the was no rattle with the chassis outside of the cabinet, I installed the chassis with about 1/2 of it hanging outside of the cabinet. There was a very slight amount of rattle. The further I pushed the chassis into the cabinet, the worse the rattle became. With the chassis all the way into the cabinet, but not screwed down, the rattle was very bad. I noticed that as I tilted the chassis in the cabinet, the rattle changed slightly, getting slight better, but not going away. Tightening the mounting screws made it worse. I checked to make sure that nothing was touching the speaker basket (the output transformer is very close but not touching). I checked all of the wiring to make sure that nothing was rubbing or rattling anywhere. If I press on the glass part of the tube, the rattle is noticably reduced.

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Post subject: Re: My Modded Champion 600
Posted: Mon Oct 31, 2011 9:55 pm
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I mean really tight, crank those babies down. If need be, lay the amp on each side to lean on those screws. :idea:

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Post subject: Re: My Modded Champion 600
Posted: Mon Oct 31, 2011 10:00 pm
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shimmilou wrote:
I mean really tight, crank those babies down. If need be, lay the amp on each side to lean on those screws. :idea:


I tried it with the screws slightly more than finger tight and cranked down really tight. No difference. I have been known to strip Grade 8 bolts. :lol:

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Post subject: Re: My Modded Champion 600
Posted: Tue Nov 01, 2011 5:57 pm
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BlueSky, Just a thought, Since the vibration went away when the chassis was out of the cab, is the speaker and baffle board good and tight? Also since the grill cloth is thinner than what it came with it might not fit quite as tight. Thinking when the chassis is in it might just be loose enough to cause the rattle. Seems most of the rattles I have had over the years was more cab, speaker, or baffle board related.

FWIW

Either way, nice build and very nice documentation of your rebuild :!: Thanks for sharing. Let us know when you find out what caused the rattle.

T2

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Post subject: Re: My Modded Champion 600
Posted: Tue Nov 01, 2011 10:22 pm
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T2Stratman wrote:
BlueSky, Just a thought, Since the vibration went away when the chassis was out of the cab, is the speaker and baffle board good and tight? Also since the grill cloth is thinner than what it came with it might not fit quite as tight. Thinking when the chassis is in it might just be loose enough to cause the rattle. Seems most of the rattles I have had over the years was more cab, speaker, or baffle board related.

FWIW

Either way, nice build and very nice documentation of your rebuild :!: Thanks for sharing. Let us know when you find out what caused the rattle.

T2


Thanks.

No, I don't think it is the cabinet. Everything has been put back together nice and tight. That was the first thing I checked. A couple of other things I noticed tonight, with the guitar volume at about "6" and the amp at "12", there is no rattle. Turn the guitar up all the way and it rattles like crazy. The rattle is the classic "broken glass" sound of a microphonic tube, not a buzz like a cabinet rattle. Also, with the tube itself out of the chassis, tapping lightly on the tube with my finger I can hear what sounds like the elements inside rattling. The new tube and damping ring should be here in a day or so and I will start trouble shooting again when they arrive. I'll definiftely triple check everything that has been suggested. I'll post what I find.

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Post subject: Re: My Modded Champion 600
Posted: Wed Nov 02, 2011 9:22 pm
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SUCCESS!

Well, the new 6V6S and damping ring arrived today from Eurotubes and as soon as I got home, I ran up stairs to plug it in and try things out.

It made absolutly no difference. Still a horrible rattle. :(

So I poked around some more inside the amp checking everything. I would strike the offending note and press on the cabinet, underside of the chassis, the transformers, etc. The rattle would change slightly. I made sure there was nothing loose on the PCB.

In the process, while I was checking things with the chassis loose and moving the chassis around slightly in the cab, I found that something was shorting out and causing the sound to drop out. I examined things closely and found the solution to that problem pretty quickly: the terminals on the Alpha pot I used for the volume control were quite long and when I lifted the front of the chassis, they would short out on the aluminum shielding on the inside top of the cabinet. I rotated the pot 90 degrees and that problem was solved.

So I buttoned everything up and continued poking around. I hit the note hard and pressed on the 5751 .... The buzz stopped! I pulled out the 5751 and swapped in my spare. I buttoned everything up and hit the note and .... nothing but pure, sweet tone. No buzz. No rattle. The first 5751 was badly microphonic. :shock:

I popped the tube shield back on the replacement 5751 and just sat and played. This thing is now a beast. With the 5751, JJ 6V6S, and Jensen speaker, this little amp is LOUD. At the same time it is very touch sensitive. Pick hard and you get terriffic overdrive. Pick lightly or turn the guitar volume down (the amp stays on 12) and it cleans up beautifully. Without the tone stack, it has a great midrange tone and very good bass for a 6" speaker. I don't even need the LPB-1 in front of it to get sweet overdrive. Well, you might want to use the LPB-1 if you want to play death metal. :lol:

Well, this project is finished. Time to make some music. :D

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Post subject: Re: My Modded Champion 600
Posted: Wed Nov 02, 2011 10:33 pm
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Outstanding!

Can you return the microphonic 5751 for exchange, refund, or credit?

Rawk on!

8)

Arjay

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Post subject: Re: My Modded Champion 600
Posted: Thu Nov 03, 2011 1:50 am
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Retroverbial wrote:
Outstanding!

Can you return the microphonic 5751 for exchange, refund, or credit?

Rawk on!

8)

Arjay


I'm looking into it. Problem is, the two 5751s were purchased from different sources. I contacted one of the two sources (an individual seller who I have met in person and is well known on TGP) and gave him the information that was on the box and the numbers off the tube and asked if that was his. The other seller was Tube Depot or Tube Store. I don't remember which and can't find the receipt. However, that tube was used for a while in my BDRI with no problems. Unfortunately, I don't remember which one it was.

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Post subject: Re: My Modded Champion 600
Posted: Thu Nov 03, 2011 2:15 am
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Good you fond trouble and fixed it

For myself if a tube is rattling, I never thinking using those ring; I replace the deffective tube.

Because soon or later withot without ring, the tube will stop to working


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Post subject: Re: My Modded Champion 600
Posted: Thu Nov 03, 2011 4:48 am
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stratele52 wrote:
Good you fond trouble and fixed it

For myself if a tube is rattling, I never thinking using those ring; I replace the deffective tube.

Because soon or later withot without ring, the tube will stop to working


I never suspected it was the preamp tube. I was sure it was the 6V6S since the tube sits within a inch directly behind the speaker, so I bought a new 6V6S and damping ring for the 6V6S. Turns out the problem was the 5751. So now I have a good spare 6V6S (the original tube I installed) but now need to get a spare 5751 since the first one was bad.

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Post subject: Re: My Modded Champion 600
Posted: Thu Nov 03, 2011 5:01 am
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bluesky636 wrote:

I never suspected it was the preamp tube. I was sure it was the 6V6S since the tube sits within a inch directly behind the speaker, so I bought a new 6V6S and damping ring for the 6V6S. .


Ok I understand you have good reason to buy tube ring . My poor American reading


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