Troubleshooting help please

[richardph]

Hello fellow grailtonies. I've had my ED for almost a year with NO problems. Moderate use, @8 to 10 rehearsals/gigs a month
at concert volume, plus a couple hours a week at bedroom volume. All of a sudden I'm hearing some "crackling" noises from the
amp, even when I unplug my guitar and pedal board. Without anything plugged in I tapped each power tube a little so see if it
made a difference, either worse of better but it didn't. Clean (green) mode seems to clear it up, but when I crank it a little its still there, and when I switch to blue it's really apparent. Could it be one of the pre-amp tubes?? If so what is the best way of trouble
shooting it (ie. swapping 12AX7's out individually etc), and if that procedure is recommended, what is the best way to check them out. I have a 1X12 combo, is it o.k. to turn it upside down for easy access to the tubes, or is it better to just put the amp up on a
workbench or something? Or, if you think its' something else, let me know. I've got 2 shows this weekend so I'm stressing a little.
Of course when I'm playing, you don't notice any of the "crackling" noise. I thought it might be some sort of electrical interference
so it tried a plug on the other side of the house, same thing. What I'm really trying to avoid is catastrophic failure during a gig.

Any input is greatly appreciated...I trust you guys.

Rich

 

[JOEY B.]

Throw the bypass Reverb switch on the back of the amp and try replacing V4 and/or V5 preamp tubes. If you can get the problem to occur in the clean channel, the issue is early in the signal chain, or in the driver, power tubes.

V1= Hi Gain
V2= Hi and Lo gain
V3= Hi and Lo gain
V4= Clean
V5= Clean/FX Return
V6= Reverb
V7= Driver

 

[tubby_cosmos]

hey I had the same problem with my ED. Swapping preamp tubes worked once. Then it happened again. After asking around, I found out that you can get that same crackling from a non-microphonic power tube. Tried swapping the power tubes, and surprisingly, it was fixed. If you have an extra set of power tubes lying around, definitely try plugging those in.

I actually called Mesa about this, and although they were very nice in dealing with me, they didn't offer any real solution. The guy I spoke to said it was likely that I just got unlucky with tubes. I suspect, actually, that the ED needs a bit longer to warm up than you might expect. It happened once to me about 6 months in (power tubes, that is) and started happening again recently (another 6 months), but what I've found is that if I let the ED sit for two minutes or more before flicking it off standby, I don't get the crackling.

If this becomes a recurring problem for you, call Mesa and see what they say. Maybe you could describe the problem to them better and find a solution. They basically told me that there was nothing in the amp that could cause tubes to go like that, so I was probably just unlucky, but having to swap out power tubes twice in a year, plus preamp tubes once is a bit ridiculous. I don't have the dough to ship my amp to them, and I'm not gigging enough right now to justify paying a tech to check it out, but I would love to have this mystery solved. If I have to go through another set of tubes in the next year, I'll probably have it looked at, but for now, extra long warm-ups seem to help.

 

[J.J]

Poping and crakling is most likely the power tubes. The actual noise is probably a result of thermal expansion inside the tube and kind of like a tin roof making noise in the sun. As tubes age they become less mechanically tight inside. There is probably an bad analagy in there, but I'll leave that alone.

My first set of power tubes (Express 5:25 not Electradyne) started making noise afer 11 months of 2 hours use a day. The ED combo is a little unfortunate in that it has 4 power tubes and they are biased on the warm side meaning they get hotter than some of the other Mesa amps. The tubes also hang upside down and the lack of a fan means the heat is trapped. ED power tubes get backed fairly well so I am not to surprised that you guys are getting failures after 6 months with good use. ED heads should be nicer to the tubes than the combo.

New production tubes are just not that good and there is not really that much incetive for the tube makers to make reliable tubes since the military does not use them anymore and they would rather sell you tubes every so often rather than once only !

A crackly power tube will not usually just fail, but over time will get worse and worse. At the start the noise will probably only just be audable. A lot of ED owners probably have the starting of crackling power tubes, but just have not noticed it yet.

 

[Birdy]

For me, V1 always does the "Rice Krispies" theme. Snap, crackle, pop.
Between 2 EDs, I've gone thru 3 JJ tubes, all in V1, in about 4 months.
I have 2 JJ pre amps tubes left, when they are done, I'm done buying JJ tubes.
All my gigs are in my basement :mrgreen: so it's not a big deal when a tube cooks.
No problems with power tubes here.

 

[richardph]

Thanks for all the great replies people. Looks like V4 was the noise culprit so Joey B. gets the prize. Replaced a couple other preamp tubes as well as I was swapping...kept track of which ones so I know which ones to start with next time (maybe). I ended up replacing all 4 power tubes as well, as on inspection I noticed that there was a slight blue glow in the glass when powered up. I heard that might not be a terrible thing, but could be a precursor to going bad. New tubes have no blue glow so it must have been time. I reckon once a year for power tubes is not all that bad, if you're playing on a regular basis.
On a side note...the preamp tube protectors are a ***** to get back on properly because of the tight fit
supplied by the o-ring. Maybe I didn't have the right leverage as I didn't remove the chassis, but I ended up putting a couple of of the protectors on without the o-rings. Appear to be secure.
Thanks again for all the suggestions. We're ready to rock again this weekend

 

[jtED]

Thanks for all the great replies people. Looks like V4 was the noise culprit so Joey B. gets the prize. Replaced a couple other preamp tubes as well as I was swapping...kept track of which ones so I know which ones to start with next time (maybe). I ended up replacing all 4 power tubes as well, as on inspection I noticed that there was a slight blue glow in the glass when powered up. I heard that might not be a terrible thing, but could be a precursor to going bad. New tubes have no blue glow so it must have been time. I reckon once a year for power tubes is not all that bad, if you're playing on a regular basis.
On a side note...the preamp tube protectors are a ***** to get back on properly because of the tight fit
supplied by the o-ring. Maybe I didn't have the right leverage as I didn't remove the chassis, but I ended up putting a couple of of the protectors on without the o-rings. Appear to be secure.
Thanks again for all the suggestions. We're ready to rock again this weekend

I know this post is been resting for a while but I thought I'd add my 2 cents as well. I bought my ED a couple weeks ago. Brought it home from the store to crank it up and found that it had a bad tube (V4). I only changed it because I was getting fart-like static in the clean channel, but realized how much clean headroom I was missing after changing out the tube. I didn't get the desired result until I tried a second 12AX7 as the first one I tried continued to make static. The dealership gave me a tube under warranty which mesa is awesome for offering the 6 month tube coverage. For the record, I also struggled with the tube retainers.