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Post subject: Trouble shoot Blues Junior I (and dating).
Posted: Wed May 02, 2018 2:37 pm
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I got this amp secondhand after doing some research on a nice tube amplifier to upgrade from a line 6. The amp is fitting with JJ tubes which I know are preferred choice for this amp. I seem to be getting rattles on harder strum chords and I'm not sure if it's the reverb tank or maybe just tube maintenance. Not sure if it's my guitar, but the amp also picks up every single interference (my S/O says aliens are trying to communicate) when my hands aren't above the humbuckers.

I got the amp for around 250$, I was thinking of creating a new casing for it (the current one is beat up I would separate the PCB from speaker creating a faux head type deal I've seen around) and changing out the speaker in the process.
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Any consolidation on rattling would be great, in my opinion it seems like the tubes are old but I would like someone else's second glance. Tubes don't make any noise when tapped with a pencil, makes crackling noises when starting up. I noticed V5 is also very red, not sure if that's completely normal. Thanks in advanced.


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Post subject: Re: Trouble shoot Blues Junior I (and dating).
Posted: Mon May 07, 2018 1:46 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14047
Location: Province de Québec, Canada
Not easy to answer.

Ouput power tubes could be the issue , they are 2004 tube or others ( 12XX7 )
Remove reverb tank from amp.
Remove back cover.
Check all screws ; speaker , baffle, transformers, chassis to cab ...Don't over tightened

And listen noise


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Post subject: Re: Trouble shoot Blues Junior I (and dating).
Posted: Mon May 07, 2018 6:21 am
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Location: Denver, CO, USA
In that dark picture, one of the EL84 power tubes is red-plating -- running way too hot.

Try switching those two tubes -- put the one that's glowing red hot in the other socket.

If the normal tube remains normal in the other socket, and the red hot tube glows red hot in the other socket, you've got a bad tube.

If the normal tube starts glowing red hot in the other socket, and the currently red hot tube works normally when it's in the other socket, the amp has an internal problem.


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Post subject: Re: Trouble shoot Blues Junior I (and dating).
Posted: Mon May 07, 2018 6:41 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
strayedstrater wrote:
In that dark picture, one of the EL84 power tubes is red-plating -- running way too hot.

Try switching those two tubes -- put the one that's glowing red hot in the other socket.

If the normal tube remains normal in the other socket, and the red hot tube glows red hot in the other socket, you've got a bad tube.

If the normal tube starts glowing red hot in the other socket, and the currently red hot tube works normally when it's in the other socket, the amp has an internal problem.


+1000


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Post subject: Re: Trouble shoot Blues Junior I (and dating).
Posted: Mon May 21, 2018 8:34 pm
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Joined: Sat Mar 20, 2010 2:30 pm
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Location: A Land Downunder
strayedstrater wrote:
In that dark picture, one of the EL84 power tubes is red-plating -- running way too hot.

If the normal tube starts glowing red hot in the other socket, and the currently red hot tube works normally when it's in the other socket, the amp has an internal problem.


Yep, on an older amp it could even be just that the tube socket needs re-tensioning of the pin holders/springs, there might be a poor contact issue on the tube pins causing the bias to get out of control and redplate the tube.

http://billmaudio.com/wp/?page_id=171


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