Is this part of the reason why my amp volume keeps dropping out and coming back? It sounds like someone is lowering and raising the volume, sometimes it doesn't do it at all.

I replaced the preamp tubes because that's what I thought it was, but no dice. Yes, it's a Bugera 333, but it kills my crappy SS Marshall MG102CFX.

No, I can't afford to buy a new amp, I have to keep this one going, for now.

In for the answer, I've had an amp do this.

The guy I talked to at eurotubes said that was a common problem with the Bugera amps, bad solder joints.

I took the head out and found a few, that pic was taken before I did any soldering. But that mess where the power switch wire and fuse holder wire goes is making me sweat.  

If you can, fire the amp up with the PCB's exposed. Get something that is insulated and start tapping on various connectors, solder joints, and the like. Maybe you can get it to malfunction. That might get you into the general area of the fault. The solder joints that I see, although messy, don't look bad. Then again I've seen a wire that looked soldered but with closer examination was just sort of 'poked' into the solder. Also, make sure the input jack isn't getting flaky. The input jack on my Fender Blues Deville had broken solder joints and made all kinds of noise and signal dropout.

Cheap pcb with poor breakdown voltage; ionizing and arcing.

If it turns out that it isn't the solder joints, it could be the power tubes. They can dip out like that when they're starting to crap out.

Out of curiosity, what type of power tubes does it have, and what is the bias set at?

The guy I talked to at eurotubes said he highly doubts it's the tubes, and I was ready to buy a re-tube kit from him, he said the most common problem with todays amps is bad soldering since most PCBs are dipped instead of hand soldered.

He was more than willing to sell me something I didn't need, but he said it really sounded like cold solder joint(s). It has JJ 6L6GC power tubes, and when I replaced the preamp tubes I bought JJ ECC83S.

The amp had Bugera 12AX7 preamp tubes, they're probably the original tubes, considering the power tubes were changed at one time, not sure as I'm not the original owner.

I have no idea what the bias is set to as I don't currently (lol) have a bias probe, I'll probably get one from eurotubes since they were so honest and willing to talk to me about my problem.

Now, what I found and addressed so far:

I re-soldered the circled areas, the one with an arrow actually has a crack in the solder, so I went ahead and fixed that up as well. The burnt areas are just from someone doing some horrible soldering, not arcing.



Next, the yellow wire coming off of the fuse holder was horribly soldered, I don't know if you can see the bare wire, but it was barely soldered on there so I touched that up as well.



Finally, I looked at the previous tubes, and noticed a bent pin, so I looked at the socket, and one of the contacts that the tube plugs into was pushed over to the side, and the pin from the tube was not going into the center, it was being bent and pushed outside of the contact in the socket.

I didn't get a pic of the socket, but I did take a pic of the old tube, I pulled the first tube out and that was the one with the issue. I bent the contact back to the center so that the pin would plug into the socket as designed.

Pic of a 12AX7socket with the offending contact marked.



Pic of the tube that came out of the socket:



I played for a solid 3 hours last night after I got done with the repairs. Nothing as much as a hiccup, the amp actually sounds a lot better, so hopefully this was my issue(s) and I can get another 8 months out of it.

This amp was made in 2008, so 7 years out of a $500 amp isn't bad.  

Oh yea, one more thing that caught my eye, is this trace appears to need some solder. May as well hit that before I close it back up, it goes to the first preamp tube, the one with the problems, and runs over to one of the power tubes.

That could become an issue one day. There are a lot of places on the PCBs that have been re-soldered by someone with some skills, the other solder job, not so much. Practice is the key.  

The trace is copper and doesn't need solder. If you have an effects loop, try bypassing it. (Plug a path cord from send to return)

That's why I said if it turns out that it isn't a solder problem. And Bugeras are notorious for shoddy components & workmanship. He was being nice.

Also, power tubes do wear out. By most standards, 7 years is kinda pushing it for an amp that gets played regularly, unless the bias is set really, really cold. But according to what I dug up, the Bugera 333s have a bias range of 38-42ma dcv @ 480v on the plates, which is ranges from just right to hot. The 6L6 chart in the link below shows bias ranges for various plate voltage ratings.

http://www.tedweber.com/webervst/tubes1/calcbias.htm

And as far as a bias probe goes, you can check bias with any decent Digital Multi Meter. I use one I bought at Walmart for $20. Someday I'll get a better one, but for now, it works. There should test points in the amp on the main board near the bias trim pot. If not, you can get the readings directly off of the bottom of the socket pins, which is what I have to do this with my VTM120 that I modded for adjustable bias.

Yea I know, but I don't have the money people want for a good tube amp today. I'm sure you've seen the prices on the good Marshall amps, and anything comparable may sound good but are made with crap components.

So this is where I am, and anything that I have now I need to run into the ground and drive it back out and keep going.

I realize the tubes should be replaced, some people do this once a year, but I didn't want to sink $80 + into an amp that may be on it's way out, hence my asking for help.

One suggestion was exactly what I was told to do from my talk with eurotubes, chopsticks and start tapping where I think the problem may be, which I already had a good idea where the trouble was.

I'm going to wait on the bias probe, as it's much easier to remove 6 screws to check the bias as compared to removing 12 plus removing the head unit. $25 isn't too much for a good tool, I already have multi meters.

Worst case scenario: the amp craps out and it's back to the Marshall MG and it's back to looking for another used POS tube amp, maybe I'll look into the B-52 AT100 212 or something.

As always, I thank all and appreciate the useful information I've been provided, and props to the peanut gallery as well, I guess. I'm no electronics tech, but I do know my way around some things.

I don't get what the idea of running a patch cable from the send/return on the effects loop does, so I guess I'll google that.

Sorry if I came across like a dick.

I've been there, so I can sympathesize.

Not at all, you seem to always offer some good advice and are helpful anytime I've come in here with questions. I should use these things more often,

Sometimes it's hard to tell if someone is being an ass or not without them, and by someone I mostly mean me.  

So far the amp is working great, I think I'll just go ahead and order the power tubes along with the bias probe, it is sounding kind of flat. The bitch is I don't have the foot controller so I'm stuck still using my distortion pedal.

I found one one ebay for $75 or best offer,  Plus, the cabinet took a beating at one time and it's shot, so I don't know what I'm going to do about that either. There's no fixing powdered wood, lol.  





Have a great 4th!  

Can somebody please explain why tube amps are still being used?



I heard that these new-fangled transistor solid-state thingys are the tits.

Thanks, glad to hear soembody limes my advice.

And I'd get a set of Ruby 6L6GCMSTR tubes. They're the same Shuguang tubes that Mesa sells as the STR-440. I have a set in my Rectifier and they sound great.

Tubes tend to sound livlier, plus you can mod a tube amp circuit fairly easily. And there's some nostalgia involved.

Tube amps are bright, clean and clear, distorted or not. Solid State amps sounds like someone wrapped your amp in aluminum foil and stuffed your ears with steel wool.  

SS amps suck, I've used both and prefer tubes amps, the tonal difference is really like night and day. If you really want to hear the difference, play your favorite SS amp and then plug into a tube amp.

Hmmm, the JJ 6L6GC's that are in there now have a sticker on the base that says "Ruby". Do they just test and match tubes? I was really wanting to go with eurotubes JJ 6L6GC-DM, not sure of the real difference:



I play mostly classic metal, think Ozzy, MegaDeth, as well as Godsmack, Disturbed and so on. That's pretty much my tonal range, I don't like the heavy bottom end from my amp, I prefer a more "punchier sound".

Not saying I don't like that sound, it's just not the direction I'm looking to go. What type of music do you play, and are these tubes more driven towards a heavy bottom end or more of a punch through the drums and bass?

Thanks!

Yeah, 6L6s tend to have a bigger bottom end. If you're looking for strong mids throw a set of EL-34s in it if it has a bias switch that lets you switch between EL-34s or 6L6s.

If it doesn't have the bias switch and you're stuck with 6L6s, you can try 5881s. They're basically a shorter version of the 6L6 that has a stronger midrange.

And I didn't know about those JJs, must be fairly new. And yeah, Ruby is a company that buys from other companies and then tests & sorts. Mesa and Marshall do the same thing.

There are only three factories in the world that make tubes. Shuguang in China, New Sensor in Russia (owned by the guy that owns Electro Harmonix and they market tubes under the Electro Harmonix, Svetlana, Sovtek, Mullard, Tung-Sol, Gold Lion, and maybe a couple others I'm forgetting), and JJ in the Slovak Republic (they're made in the old Tesla factory).

There used to be a fourth manufacturer in Russia named Svetlana, but due to New Sensor screwing them out of the rights to their name here in the US, they started selling their tubes under the SED =C= label, aka Winged C. They made some of the best modern production tubes, but unfortunately they went out of business a couple years ago, and what's left is their B stock stuff.

Oh yeah, and I play all sorts of stuff. Mostly metal & classic rock but I dabble in blues and old school country.

Tube amps have a natural distortion, the more powwr/volume and the more distortion... and produce music.

Solid state do not distort... They just get louder and louder.  Solid state is fine for recreating music, but it sucks for making music IMHO.

There are now 'hybrid' amps with a tube or two in the curcuit that soften and distort nicely but are much cheaper to build / buy vs a true tube amp... Hybrid is about as far from a true tube I'll play.  I strongly prefer the sound of a vintage Fender amp made sometime prior to my birth.

Uhhhhhh

There are two different types of distortion (clipping) in tube amps, preamp and poweramp.

Preamp distortion has absolutely nothing to do with power or volume. It is a product of the preamp gain stages being overdriven.

Poweramp distortion is another matter. It is a product of the power tubes clipping and in some designs, the phase inverter also contributes to this (the phase inverter is actually part of the poweramp even though is is usually the same or similar type of tube you typically find in a preamp). The thing about poweramp distortion is that the more wattage a poweramp has, the more percieved headroom it has, because it has to get louder than amps with less wattage to get the poweramp to clip. And smaller poweramp conversely doesn't have to get as loud to clip.

Also, solid state amps are capable of distortion/clipping. In a solid state amp that is designed to reproduce music or transmit (such as in a CB radio), clipping is bad, doesn't sound good, and thusly are designed to distort as little as possible (every amplifier has a little bit of distortion).

But solid guitar amps do in fact distort. It's no secret that diode clipping circuits have been used with guitars for decades. Tube Screamer pedals are a good example, and even the famed Jose Mod utilizes diode clipping. Newer designs use J-Fets for Distortion, and in the case of the Bogner Extasy pedals, and others, work quite well.

But if you're talking about digital modeling amps, then yes, those amps don't get their  distortion from their components. All of those tones come from algorithms.

 
Well, yes and no. Solid state amps do distort, and that distortion becomes a square wave. It also pushes like a master track limiter as volume increases. There are a few phenomenon at play that make people tend to go towards tube amps.


1. The naturally occurring mid reduction as volume increases.


2. The preference of louder things sounding better.


3. Tube amps distort with rounded waves while solid state amps distort with square waves.


4. Round waves sound better than square waves at high volume (most of the time).


These four things make the tube amp the preferred amp. My personal preference goes as follows:


Am I playing at a low to medium volume? I prefer solid state. It doesn't even need to be very much wattage; 30 will do.


Am I playing at a high volume? I want tube. 50w+ only, please.

I was trying to keep it simple, but I don't disagree with what you wrote.

I think distortion in pedals is a world apart from distortion from amps.  I have pedals that are solid state that distort the signal musically and sound great, i have never encountered a solid state amp that distorted in any sort of 'nice' way.... maybe I need to play more of them when I'm out at shops.
I'll probably continue to stick with tubes though. (current pile is black and silverface Fenders from Champ to Twin Reverb in size and a few old Traynors)  I read this thread with interest as the 1960 Infinium from Bugera keeps popping up on my radar as a fairly inexpensive way to add Marshall type tone to my options.

Cool.

The main reason I mentioned the Bogner Extasy pedals is because they are essentially preamps, and I have used my Extasy Red in that function, directly into the poweramp of an existing amp. It works great.

And there are some good sounding solid states out there. Dimebag Darrel used nothing but solid state Randalls up until his Damage plan days, if you're a fan of his tone. The Peavey Bandit 112 (Transtube versions), Supreme, & XXL, and Quilter brand amps are also good sounding solid state amps.

But that said, I still prefer tubes.