Faulty tube or faulty amp?

[snakestretcher]

Fired up my Express 5.25 1x12 and switched it-for the first time since I oened it-to the 5W setting and noticed blue arcing in the left hand power tube, as viewed from the rear. What's going on, bad amp or bad tube?

Thanks.

 

[EtherealWidow]

Does it do it consistently? Might be a bad fuse.

 

[snakestretcher]

Does it do it consistently? Might be a bad fuse.

I switched on very briefly and it was arcing during that time. The amp is barely a month old.

 

[EtherealWidow]

Sounds like a fuse thing to me, but as always I'd like a second opinion from someone else. I'm kinda inexperienced. Switch the fuse, then try it again at somewhere else. Your electricity might be bad. If it's still doing it, maybe it's the power tubes. After switching those out, might be the amp. :/

 

[MrMarkIII]

A "bad" fuse is a blown fuse. The amp will not work at all with a "bad", i.e., blown fuse. WTF?

 

[EtherealWidow]

As I said, kinda inexperienced. Plus, the amp can short out and arc, thus blowing the fuse while it's turned on. Says it right in the manual. No need to be an ***.

 

[Don]

Arcing or glowing blue?

The power tubes will have a blue glow. It's normal. Here's mine-

Arcing would be bad.

 

[snakestretcher]

Arcing or glowing blue?

The power tubes will have a blue glow. It's normal. Here's mine-

Arcing would be bad.

Looks more like the blue glow in the photo but only one was glowing blue and it was instantaneous the moment I switched to Class A, 5W. Both tubes looked normal when in Dyna-Watt mode.

 

[BoogiePete]

I could be wrong but I think 5w mode only uses one output valve. There was a thread on here about it somewhere but couldn't find it. If your amp isn't doing anything strange ie popping, crackling, lack of tone or power then I'd say all is well!

 

[snakestretcher]

I could be wrong but I think 5w mode only uses one output valve. There was a thread on here about it somewhere but couldn't find it. If your amp isn't doing anything strange ie popping, crackling, lack of tone or power then I'd say all is well!

Yeah, thanks Pete, and you're right. I called Manson's where I got it and spoke about my concerns and it appears all is well. The blue glow is a result of more current being drawn in Class A (I believe). What bothered me initially, and caused some confusion, was that both valves glowed the same colour in full power mode. I had it up and running for a couple of hours today and there doesn't seem to be anything amiss.
How's sunny Tavistock today? (I'm in Exeter).

Cheers.

 

[BoogiePete]

Cool! Glad all is well. Bought my Les Paul Traditional from Mansons about a month ago, tried it out through the MK5. They have some lovely kit in there and always seem helpful. Nice shop!

Sunny Tavistock!!! Pi**ing down as usual! :lol:

 

[Don]

In 5 watt class A SE mode, one tube glows blue brighter than the other in my amp.

BTW, I failed to notice that you were talking about a 5:25, my amp is a 5:50!

 

[jpdennis]

Looks more like the blue glow in the photo but only one was glowing blue and it was instantaneous the moment I switched to Class A, 5W. Both tubes looked normal when in Dyna-Watt mode.

And you can put it on standby before you switch to Class A :?: In the late 1960s and early 1970s there used to be warning guides with the tube guitar amps about letting it warm up for at the very least 5 minutes before active use and always placing the amp in standby for a minute or so prior to turning it off. I do not know about any new safeguards. This way power tubes don't have an early death as well as other components. One of my techs has even told me to put the thing on standby prior to switching to Class A and back. He also pointed out that giving the thing a 20 minute to 30 minute warm up makes it where the amp doesn't change tone as everything comes alive in the midst of playing. This way I do not have to readjust my tone or volume after the first several songs. :wink:

Dennis

 

[soundchaser59]

I was told at the dealer to always put it in standby before switching power modes. So I always do.....

 

[J.J]

The Mesa manual for these amps states that you should let the tubes warm up for at least 30 seconds before switching off standby. Tubes don't like to have the high voltage applied until they are warm or 'cathode striping' occurs. On a less technical note, performance of the tubes decreases far more rapidly if you don't let the tubes warm up. Both tone and volume will be lost.