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Tube Amp Problem

adlankj

By adlankj
in The Gibson Lounge

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adlankj

adlankj

Posted
Posted

So, last night my new tubes arrived for my BJr, and I decided to put them in this morning. However, when I put in the tubes, I couldn't get any sound from the amplifier, unless I cranked it all the way (volume and master at 12), and then it's just a barely perceptible sound.

 

the tubes are 2 Jan Phillips 5751s, 1EHX 12AY7, and 2 Gold Lion el84s.

 

Just a bad tube or few tubes right? Well here's the kicker: I put in the old tubes again and I have the same problem, no fix.

 

Yes, I'm planning on calling Fender customer support later, but I can't right now, so if any of you have an idea of what's wrong, could you tell me?

 

Thanks in advance.

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djroge1

djroge1

Posted
Posted

Make sure all of the tubes are all of the way in. Put all of the old tubes back in again then take a wooden chop stick and lightly tap on each tube and listen if there is a change. Also try and lightly push on the tubes with the chop stick.

 

Replace the tubes one at a time.

 

My guess is that you didn't get the tubes seated properly.

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adlankj

adlankj

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There really isn't anything you can bump into on the way to the tubes on the blues junior. I tried what you suggested droge, but nothing seems to be happening. I just don't know what the problem is, and apparently Fender doesn't have a customer support line, you have to take it to a service center, and since I'm in Jamaica I guess that means I'm screwed, huh? Who the hell doesn't have a costumer support line at this day and age?

 

I should mention that at one point yesterday, I had all the new tubes in, and I replaced the V1 tube with one of the old ones, and it started working again for a minute or so, and then the volume slowly died down into nothing.

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NeoConMan

NeoConMan

Posted
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I'd say it's a tube problem....

 

[biggrin]

 

Okay, I know that doesn't help any - sorry!

 

:-k

 

 

 

I really got nothing for you if the old tubes do the same thing.

Why were you swapping tubes if the old ones were working?

 

[biggrin]

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milod

milod

Posted
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I'd hoped somebody who knows a lot more than I do would get onto this, even though I'm from the era where a cupla times a year I'd replace tubes in various radios or televisions around the house and...

 

Anyway, I wonder also if there's something simply in the connections for the tubes - the stickie-in places where the stickie-out parts of the tubes go. Lots can go wrong with connections when you're swapping tubes.

 

Do the tubes warm up and glow, or do they stay cool? If they never warm up, they're not getting electricity and can't do their jobs. That's frankly how I always figured what tubes were bad in radios, TVs, guitar amps and PA systems. Then I'd take the cold tube to the "doctor" and in those days everybody had a test machine.

 

BUT>>>> Sometimes when replacing a bad tube, it didn't seem to work because there would be dirt or physical disconnection involved in the "female" attachment in the radio/amp/tv/pa that kept the tube from getting electricity.

 

So... Back in those days I was sufficiently energetic and there weren't the "broken warranty" issues of today so I'd take stuff apart enough to clean the contacts and make sure wires looked connected and didn't get turned or twisted so as to make a short circuit. Then I'd replace tubes and...

 

If something else in the amp is "sick," that doesn't help. The "they start working and then don't" could be from dirt, messed up wire that moves when stuff gets warm ... other stuff ... everything has to work together in electronics.

 

The advantage I had back then was that there were two "radio and tv repair" shops on Main Street even in a town of 1,500. Both had tube test machines "up front" that they'd even let a 12-year-old use.

 

m

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SHO

SHO

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It could very well be a mechanical error, as Milod suggests. The contacts in the tube socket can lose tension overtime, or become deformed if a tube wasn't inserted properly, which means they wont make a solid connection with the tube pins. In power tubes the heat being led down through pins can also cause problems.

 

I'm not very familiar with Fender amps, so I have no clue, but if the tube socket is mounted directly to the pcb you could have wiggled it enough to make a solder joint to break. This could also happen to, but it's a lot less likely, to chassis mounted sockets with wires going down to the pcb. Or the turret board for that matter.

 

Another possibility is that one of the new tubes was faulty and shorted something, causing some other component to die within the amp, which explains the old tubes not working either.

 

It could be a lot of likely and unlikely things, to be honest. It would be helpful to know if the heater filaments glow, for example. There are a bunch of little tests and fixes you can try, however they either include manipulating the tubes while the amp is running, or sticking tools into the tube sockets while the amp is off but that requires certain knowledge that it is fully discharged, and as such I don't really recommend trying any of them to someone who doesn't know their way around electronics.

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milod

milod

Posted
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Sho pretty well hit it all except for a slight bit of explanation here...

 

He alluded to not sticking metal things in there unless "it is fully discharged."

 

There are "capacitors" in there that hold a charge of electricity. Some could damage you or the amp.

 

That's kinda like the flash on your camera. It takes time between flashes or to "warm up" because the batteries are charging up the "capacitors" that are kinda like short-term batteries holding electricity. I was cleaning batteries on an old camera flash, hit the wrong little bits of metal on the capacitor connections and then hadda pick myself up off the floor.

 

Bottom line... Were I you, I'd try to find a qualified tube-type repair person. if there are additional questions.

 

m

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adlankj

adlankj

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Thanks so much for your help you guys, I got the problem fixed.

 

Through my teacher I found a person who could help me and found the problem. He runs a studio place, but as it turns out he knows a lot about guitars.

 

Apparently, I pushed too hard when installing my new tubes, and damaged some of the sockets. I should learn to be a lot more gentle when dealing with my amp, because honestly I didn't feel like I applied that much pressure, I thought I was just slipping them in.

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milod

milod

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Hey, you did the right thing: Found somebody who knew what they were doing. Saves a lotta cash in the long run.

 

And don't necessarily feel bad about the tube thing... We all learn the hard way. At least, I did too!

 

m

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