So I bought a used Bugera 6262 (non-infinium). This is my first tube amp, and I don't know what I'm doing. It came with the original tubes, which must be pretty old by now. I'm running it on the 8-ohm setting into an 8-ohm 2x12 cabinet. The first couple of hours playing yesterday were great. Today nobody was home, so I put an MXR 6 band eq in the effects loop and cranked it up loud to dial in a tone. After about 5 minutes, 2 of the four power tubes were glowing bright orange and purple (the 2 furthest from the power cable, in case that matters). The other two were glowing, just not nearly as much, and only an orange color. After I noticed it, seconds later, I saw some sparking in the 2 bright glowing tubes and heard some noises, and the sound cut out. I immediately put it on standby, and after a few more seconds, the fuse blew, and the blue power light turned off. I think the two bright glowing tubes blew, and that caused the fuse to blow. I plan to order a new tube set, both power and preamp, and some fuses). I also ordered a bias probe, so I'll be able to set it properly. So my questions are; does this sound normal when tubes go bad, or does this seem like some other issue? As I said, this is my first experience with a tube amp. If this sounds normal and the tubes were just old and bad, are there any tube brands to stay away from? I was planning on ordering JJ 6L6s and JJ preamp tubes. Thanks for any advise or input!
Hello Nate,
First, this topic belongs in the "instruments and amps" forum listed under under Live Sound (top left "forums") since a Bugera is a guitar amp. This is more for hifi stereo amplifiers. But I'll answer you anyway. IMPORTANT: Tube amplifiers use high voltage up around 400 or 500 volts that can kill you. Since you admit you're a nooby that doesn't know what he's doing, maybe you should not open it and troubleshoot it yourself, or alone. Find someone that is familiar with this type of work.
Pressing on, what you describe seems like possibly more then just a pair of bad tubes. Something may have made that happen. Perhaps a loss of negative bias voltage on the control grids (pin 5) of the output tubes in question. A bad connection, bad resistor feeding the voltage or even a leaky coupling capacitor from the previous stage. You will need some type of multimeter to check this. And yes, it could be a pair of shorted tubes as well. You'll want to test the tubes and download a schematic if you don't have one. Normal negative bias voltage on 6L6GC tubes is roughly around -35 volts. EL34s slightly less.
As far as tubes go, it's been said on this forum that octal base JJ tube are not trustworthy. I personally never use any new production tubes. Rusyk tubes are probably better if you can find them. If I had to buy tubes I would first find a reputable dealer like this one that thoroughly tests everything he sells.
Good luck with it.
First, this topic belongs in the "instruments and amps" forum listed under under Live Sound (top left "forums") since a Bugera is a guitar amp. This is more for hifi stereo amplifiers. But I'll answer you anyway. IMPORTANT: Tube amplifiers use high voltage up around 400 or 500 volts that can kill you. Since you admit you're a nooby that doesn't know what he's doing, maybe you should not open it and troubleshoot it yourself, or alone. Find someone that is familiar with this type of work.
Pressing on, what you describe seems like possibly more then just a pair of bad tubes. Something may have made that happen. Perhaps a loss of negative bias voltage on the control grids (pin 5) of the output tubes in question. A bad connection, bad resistor feeding the voltage or even a leaky coupling capacitor from the previous stage. You will need some type of multimeter to check this. And yes, it could be a pair of shorted tubes as well. You'll want to test the tubes and download a schematic if you don't have one. Normal negative bias voltage on 6L6GC tubes is roughly around -35 volts. EL34s slightly less.
As far as tubes go, it's been said on this forum that octal base JJ tube are not trustworthy. I personally never use any new production tubes. Rusyk tubes are probably better if you can find them. If I had to buy tubes I would first find a reputable dealer like this one that thoroughly tests everything he sells.
Good luck with it.
Hi Nate, Just to add to HollowState's advice....I advise not to trouble shoot by yourself as well, However, What I can advise is to look for and join a ham radio club/electronics club nearest to you.....I was very lucky with mine in Australia, There were a lot old time hams in their 60's & 70's who freely helped me out.
The knowledge that these old boys gave and taught me was incredible.
cheers.
The knowledge that these old boys gave and taught me was incredible.
cheers.
Definitely a case to leave to someone that has the knowledge and experience.
Glowing tubes are unhappy. One cause on older amplifiers is that the coupling capacitors leak a bit of DC and cause the bias to increase. You can change these yourself with modern capacitors of the same value and voltage rating. You might also change the main filter capacitors. Then there is the issue of old resistors failing. That one takes a bit of knowledge to troubleshoot.
Of course you should leave the amplifier unplugged for about a week before sticking your hand in the equipment.
Just changing the tubes is usually safe, but probably is not enough.
Keep in mind all the nice folks here who are trying to protect you from Darwin’s theory. So you might want some experienced help.
However as many here will explain to you I am not as nice as some other folks here! (Do you carry life insurance?)
Of course you should leave the amplifier unplugged for about a week before sticking your hand in the equipment.
Just changing the tubes is usually safe, but probably is not enough.
Keep in mind all the nice folks here who are trying to protect you from Darwin’s theory. So you might want some experienced help.
However as many here will explain to you I am not as nice as some other folks here! (Do you carry life insurance?)
Note that Bugera highly recommend that bias adjustments be carried out by qualified personnel!
https://www.manualslib.com/manual/537563/Bugera-Valve-Bias.html
You still have to know that it's dangerous...
We will have to get used to people not even asking themselves the basic questions.
It is enough to be convinced of it to look at some video of dash cam or other on you tube.
Access to knowledge has never been so easy and people have never used it so little...
We will have to get used to people not even asking themselves the basic questions.
It is enough to be convinced of it to look at some video of dash cam or other on you tube.
Access to knowledge has never been so easy and people have never used it so little...
Just deleted a post more or less saying the same thing. For an experienced person the liability evading warnings are not meaningful. For persons without any relevant experience or not knowing the dangers of electricity it would be best to keep out of such repairs.
Like you I notice the Youtube trend and people even thinking calculations/formulas are volatile or something for nerds. I call it "anything goes" thinking. You notice it immediately as a device has then already been opened, some unclear things have been done that need to be corrected and screws are tightened so that the thread is worn. When you fix it you get comments in return doubting the quality of your work. Crazy world.
Like you I notice the Youtube trend and people even thinking calculations/formulas are volatile or something for nerds. I call it "anything goes" thinking. You notice it immediately as a device has then already been opened, some unclear things have been done that need to be corrected and screws are tightened so that the thread is worn. When you fix it you get comments in return doubting the quality of your work. Crazy world.
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Thanks for the advice! Whatever I end up doing, I'll take it to someone qualified. I'm kind of in a bad spot. I purchased the amp from reverb last week. It was advertised as an INFINIUM version. However, after researching after having this problem, it is NOT the INFINIUM version of this amp. Had I known that, I would not have bought it as the non-Infinium models seem to be known for having bias issues. I know I took a chance by purchasing a used amp, but I did not get the amp I thought I was buying. Since I did not get what was advertised, I am now wanting to return it. 🙁
Nate
We just fixed two Bugera Amps with the same problems.
A 6200 and 6262 Infinium blowing power resistance and a tube Shorted
Screen to control grid.
What tubes are being use in your amplifier ?
We are sorry you have a major failing amplifier, but it is not uncommon.
New tubes will not help, for this amplifier needs a major checking out.
Biasing is a poor process in this amplifier - in that the bias is set to one tube
all four tubes are different to some extent as to Plate current - bias needs and filament voltage.
Hope we can help you later,
Cj
We just fixed two Bugera Amps with the same problems.
A 6200 and 6262 Infinium blowing power resistance and a tube Shorted
Screen to control grid.
What tubes are being use in your amplifier ?
We are sorry you have a major failing amplifier, but it is not uncommon.
New tubes will not help, for this amplifier needs a major checking out.
Biasing is a poor process in this amplifier - in that the bias is set to one tube
all four tubes are different to some extent as to Plate current - bias needs and filament voltage.
Hope we can help you later,
Cj
It had the original Bugera tubes in it. It's currently at a local repair shop being checked out. I dropped it off Monday. I sent a new matched quad of ruby 6l6s with it for them to put in it incase it checks out ok or the repair isn't too costly 🤞. Do you repair amps?
The bad tubes used in the Amplifier may I buy all of them from you ?
We would like to test the Bugera Tubes for High Voltage Shorting.
We have a DYNAMIC Tube tester that test the Tubes in an Active Circuit.
Tubes can short out - Screen to the control - Grid causing RED PLATE GLOW
when the High Voltage is turned on,
with warm filaments and hot cathode as in STANDBY.
Hope they can fix it the amplifier - let me know when it come back...
We fix amplifiers for our research on power Amplifier failures.
Cj
Experienced techs are thin on the ground, especially ones used to dealing with valve/tube amplifiers, this means anyone wanting to learn about the subject has to use their own initiative and by following some simple precautions it is possible for a beginner to check a few things on a valve amp safely.
The first rule with anything vintage or used is to never apply power without first checking a few things. The first thing to do, again without plugging the amp to mains electricity is to do a visual check. That means taking off the cover/s and in good light visually examine the inside. Your looking for any loose wires, burnt components or areas of scorching or anything that doesn't look right.
Next take a few good pictures of any circuit boards etc and post them on a forum such as this so that more experienced folk can have a look. All this is without plugging it into the mains electricity supply. As long as you don't touch anything with your fingers you should be fine. But be aware even without powering the amp up there are capacitors inside that might still hold a charge of high voltage, so, use your eyes, not your fingers.
In order that you can work on valve amps you'll need to first learn about the risks involved and roughly how they work, to this end before you have a go I'd recommend to sources of information, the first is The Valve Wizard site - http://www.valvewizard.co.uk/index.html and check out Uncle Dougs Youtube video channel - https://www.youtube.com/c/UncleDoug this should give you a rough idea of how they work and some of the inherent dangers of working on them.
Lastly if you can't find anyone to have a look at your amp and you do decide to have a look at it yourself you need to build a lamp limiter which is a simple device easily & cheaply made that allows you to eventually power up your amp with less risk, to the amp that is.
Andy.
The first rule with anything vintage or used is to never apply power without first checking a few things. The first thing to do, again without plugging the amp to mains electricity is to do a visual check. That means taking off the cover/s and in good light visually examine the inside. Your looking for any loose wires, burnt components or areas of scorching or anything that doesn't look right.
Next take a few good pictures of any circuit boards etc and post them on a forum such as this so that more experienced folk can have a look. All this is without plugging it into the mains electricity supply. As long as you don't touch anything with your fingers you should be fine. But be aware even without powering the amp up there are capacitors inside that might still hold a charge of high voltage, so, use your eyes, not your fingers.
In order that you can work on valve amps you'll need to first learn about the risks involved and roughly how they work, to this end before you have a go I'd recommend to sources of information, the first is The Valve Wizard site - http://www.valvewizard.co.uk/index.html and check out Uncle Dougs Youtube video channel - https://www.youtube.com/c/UncleDoug this should give you a rough idea of how they work and some of the inherent dangers of working on them.
Lastly if you can't find anyone to have a look at your amp and you do decide to have a look at it yourself you need to build a lamp limiter which is a simple device easily & cheaply made that allows you to eventually power up your amp with less risk, to the amp that is.
Andy.
The amp is fixed and I have the old tubes. Let me know if you are still interested in the Bugera tubes.