Random Loud Spurting Sound coming from my amp

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hey all,
I am in search for an answer to a problem, and was hoping you all would know more about amps then me to aid me in a answer. I currently own a 60 watt crate tube amp, V series made in America (st.louis). I also use a boss me-30 for effects, and memory boy. I havent replaced the tubes for 2 years. but they seem fine.

For the most part the am has been flawless, sounds great and has given me the tone I really want. However recently after the amp has been playing for about 20 minutes the amp lets out this awful extremely loud spurting crackling noise, it lasts for about 3 or 4 seconds a burst, but will get more and more frequent as I continue to jam.
I have cleaned out the pots, and input jacks, checked the tubes. and so far no real luck. except whenever I put the amp on stand by for a while and turn it back on, the sound will not show again for at least 15 minutes.
I have basic electronics skills, and tube skills, I know how to solder. I also know how tube amps work, I have read multiple books on them but lack field experience. thanks for taking the time to read this!
-Aaron
 
UPDATE, it almost sounds like a spring, almost like something is bursting inside the amp, but for a short really loud burst. It did come with a reverb spring box, but i have already removed that. also just FYI, The reverb tube, purely functional, blew awhile ago I think, because the reverb stopped working a while ago.:/ I am almost feeling like getting a new amp...
 
Back in the 70's we used to use two Carlsboro 200W valve mixer/amps for PA (just using them as power amps).

They both used to make internmittent 200W 'farting noises', perhaps similar to the problem you're having?.

But they were so intermittent I was never able to find what caused it (they only ever did it at gigs, never during testing). So we got rid of them and replaced them with a tiny 100W + 100W Citronic slave amp, which not only was a fraction of the size and weight, but was also considerably louder and better quality.

I don't know how you've tested the valves?, but the only real way would be to swap them over from an identical good working amp.

As long as it's reliably faulty (if you see what I mean?), it shouldn't be too hard to find the problem - first off do you have a circuit?, and what effect do the various controls have?.
 
I am tempted to just buy new tubes, just because I need them, and it might solve the problem.

Actaully the controls for the most part are always turned off on the actual amp. Except for the clean chanel. (Mid, Treble, Reverb, Gain) and I control everything from my boss me-20 (correction, not 30)
Also, when I am using just gain station on my amp, the sound still has yet to surface. This is what gives me suspicion to believe that its mabe just the tubes.

I guess what I am trying to ask is, what are the common characteristics of a blown tube?
 
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Exactly, and it not existing in built in overdrive on my amp, it makes me think the tube built for the clean channel is blown, I think thats the first or second tube.

UPDATE: It does crackle on clean channel too, :/. However if I play softly i never hear the sound, but if I reach a certain pitch on my fret board with a louder volume the crackle will surface again. Also right before the crackling session begins, you can hear a slight quieter version of the crackling.
 
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I don't know how. haha I am pretty new to the whole tube amp thing. However now I know its not a tube, got new tubes now it lets out an alien sound constantly, along with the spurting... ughhh

Its a crate 3112 v series,made in st.louis. It was a local amp thing, so i am having no luck finding a schematic. I did find the crate 3112 owners manual though
 
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If you replaced the power tubes, and the problem remained, then I'd believe the tubes were not the issue. However, that would be the most common cause.

Turn the reverb down for noise reasons, ball up your fist, and give the top of the amp a whack. The amp should sit there quietly. If hitting it makes the amp react, then something is loose inside. Probably broken solder. If that is the case, then consider that while playing the speaker vibrates the amp, and can cause the symptom.

Inside the amp, connected to a speaker and running, use something insulated - I use a wooden chopstick from the Chinese food place - and prod each part on the circuit board. Looking for anything that reacts when pushed. Most likely candidates are the larger parts. The larger 5 and 10 watt size power resistors often break free. Those are the tan rectangular cement fellows. If wiggling them makes noise, resolder them. The larger an electrolytic cap is, the more likely it is to have broken its solder, check them. And of course, check the solder on all the controls and jacks.
 
I found it, as far as I know its the same, except mines white, and has a crate plate on it, on the bottom it says made in st.louis. however it still has the name 3112 on it.
Crate V3112 schematic

Assuming it's the same, try unplugging the valve J2A/B - see if that stops it happening - this proves which part of the circuit is at fault.

If that doesn't stop it, then make sure the reverb control is turned right down (just to eliminate that) and insert a blank jack plug (or an unconnected screened lead) in the effect return socket - see what that does. The return jack totally disconnects the power amp and preamp - if it still does it, then the fault has to be in the power amp.
 
Alright so I think I fixed it...I do some poking around and after about 20minutes it started popping, sooo I gave it a whack,and it continued to do it louder. so I opened the chasis and started poking every part, I realized that after poking around there were multiple parts that rattled upon impact. Uising my little ampknowledge I knew that certain tubes run certain parts of the amp. so I poked thepower tube nearest to it, I belive it was 3, which makes sense because my reverb was broken, which is usally run by the third tube.anyways I poked, not the tube but the tube socket/cathode on the chasis and it made the popping noise. So I pulled the tube, and it rattled abit when I shook it. I turned on the amp and continued to play, and after 30 mins it has still so spurt and spat at me.

My question is, Is it the tube?or am I going to have to replace a whole cathode/socket? if so I might as well not even bother, considering I can just use the reverb on my multi-effects...
 
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