Preamp tubes, or that and more?

Discussion for the new Mark V

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Mark III
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Joined: Sun Nov 02, 2008 5:29 pm
Location: Chattanooga tn

Preamp tubes, or that and more?

Post by primeholy » Tue Jun 11, 2019 9:27 am

My Mark V 90 watt is being noise on channel 2 and 3 in the 45 watt mode. My reverb is also starting to get a really loud hum the longer it is engaged. Do these all seem like preamp tube issues, or could it be other things as well?

Mark I
Posts: 24
Joined: Tue Feb 10, 2009 5:30 pm

Re: Preamp tubes, or that and more?

Post by doublescale1 » Tue Jun 11, 2019 12:02 pm

Pre-amp tubes are the easiest place to start. look at your tube chart and start w/V1 - get a new one and swap it for whats there, if the issue is resolved then you are done, if not, go to the next one in line and repeat. If none of the pre-amp tubes seem to be the culprits, then try a new matched set of power tubes - the whole set. Make sure you note the tube type for the reverb driver, it may not be the same as the signal path preamp tubes. Process of elimination is a slow-but-steady way to see if the tubes are causing the noise.

Mark I
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Joined: Mon Dec 09, 2013 1:55 pm

Re: Preamp tubes, or that and more?

Post by jdgebha » Wed Jun 12, 2019 1:22 pm

I had a rectifier tube do weird sh!t to me on 45 and 10 watt mode not too long ago. I would check that as well.

Bottle Rocket
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Joined: Sun Mar 05, 2017 1:16 pm

Re: Preamp tubes, or that and more?

Post by Mycle » Sun Jun 16, 2019 11:54 am

I just had a recto tube crap out on me and the 45 watt setting on all 3 channels went completely dead.
I do have a new hum going on as well but I hadn't made the connection to the reverb circuit. Just hum.
So now I sit and wait for FedEx to bring me a new glass bottle of joy. (and a back up)

I will say this … when she went … she went big. The old recto tube tests completely dead on the tester.

All of the other tubes were still filled with joy.

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