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New Valve Jr - Problem, Please Help


Scott C

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Hi all, new guy here.

 

I just received a new Epiphone Valve Jr.[confused] from a reputable online dealer, delivered via UPS.

 

It works, but every second or third time I use it, it sort of shuts down after a minute ot two or three[blush] . The power light stays on, but the sound just fades away and then will return in a minute or two.

 

I am new to tube amps, so don't even where to start. Should I just return it, or is this typical, common, or an easy fix.

 

Could the cold winter weather or the UPS delivery have messed something up. Loose tube, cracked component,...?

 

An educated opinions will be much appreciated.

 

Thanks.

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Okay, first thing to do is get the back off the amp. They put the backs on while the tolex glue is still wet, so a putty knife can help break the glue seal and give you something to put against the chassis as you lever it out with a screw driver or something.

 

Wiggle the tubes around in their sockets just to make sure they're well seated. While your in there, notice the fuse holder on the orange PT wire. take the fuse out, and push the wires into the holder so you can get at those pressure pads inside. You need to buff those with a file or scotchbright pad and get any and all varnish off so the fuse will make good contact with it. Reinsert fuse, and crank it up. This issue has been a common problem since the first VJr's came out years ago.

 

If it still has problems, try new tubes. They're like lightbulbs, and won't last forever. Worse, they only burn out when you need 'em! Also, DOA tubes are common right out of the box. Best to stock up, and test 'em all as soon as you get 'em so you can take back the duds if you have to. If you take the amp out to gig, take spare tubes with you.

 

Gil...

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I'll just add be VERY careful what you touch inside a tube amp. Even when off and unplugged they can discharge (into you) lethal voltage. Where shoes with rubber soles and don't stand on concrete. Use one hand to poke around. Put the other hand in a pocket so in the worst case you won't have the voltage running across your heart as it races between your hands. I'm not familiar with the VJ so maybe the danger is no where near where Gil is directing you. Just thought I'd add this point of caution.

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there aren't any parts outside the chassis so he's not going to touch anything that could hurt him unless it's plugged in.

taking the back panel off usually anyone would unplug speaker and power cord so I can see why gil, and just about everyone who talks about fixing those crappy fuse holders leaves it out.

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there aren't any parts outside the chassis so he's not going to touch anything that could hurt him unless it's plugged in.

taking the back panel off usually anyone would unplug speaker and power cord so I can see why gil' date=' and just about everyone who talks about fixing those crappy fuse holders leaves it out.

[/quote']

I'm not sure why I over-reacted like that. I guess cause the OP said he was a newbie to tube amps. Nobody would put a fuse close enough to a capacitor to cause harm. Although my '64 Gibson Skylark's caps are just behind a thin strap of wood you'd take off to get to the tubes better. It's scary how much trouble somebody could get into in a hurry with some of the older amps. And there are no warning signs either!

 

caps_on_syklark.jpg

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That's what I love about these forums. Always someone to pick up the slack if someone forgets a step or two.

 

Yeah, DEFINITELY unplug the amp first! And let the tubes cool before touching them with your fingers.

 

Just in the act of cracking the cab open, one would assume step one would already be done, and it'd take long enough to satisfy step two.

 

But not to worry. The chassis is a ceiling-hanger type, so there won't be any exposed component leads. And, the amp already has a cap bleeder resistor on the power rail that bleeds voltages down to safe levels in about 15 minutes. I don't recommend trusting one's life to a 20 cent resistor, but it should at least make changing tubes safer in case the tube's glass envelope shatters in your hand while still plugged in. This is rare, but it recently happened to me, and I got a rather nasty shock simply because I was in a hurry and hadn't waited till the caps had a chance to bleed off their charge.

 

Gil...

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I don't mind extra safety advice, so no need for anyone to apologize.

 

I re-seated the tubes and cleaned off the fuse holder contacts (you think they could have spared another inch of wire to make that a bit easier). I played it twice last night for about 30 minutes each, and so far so good. But, I won't be convinved until it works at least 5 times in a row.

 

By the way, I was messing around with an old tube AM radio a while back with point to point wiring, and the best I could describe it was it looked like it was done by drunken monkeys.

 

Thanks all.

 

PS Go Packers!

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When I was first into this... I had this idea that the amps I knew from my youth looked that way because.. what else would you get from sears, etc., for fifty bucks or less..then I started looking at the amps that a lot of people really rave about..

and realized..it's almost like the messier the better.

Everything about a pcb board is neat looking, but not neat acting..(unless it's a turret build layed out better).

 

I think you've got your problem nailed.

I couldn't believe it when I first ran into that either.

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Well, the adventure continues[confused] .

 

The re-seated tubes and cleaned up fuse holder were working fine.

 

Yesterday I swapped out the stock EL84 with with a Ruby EL84 and played for about 30 minutes. I noticed a little less volume, but it seemed like a less harsh sound. So far, so good.

 

Today, I played a while longer and then out of nowhere, sort of a weird hum for 5 seconds or so, then nothing... except a bit of an electrical smell.[crying]

 

I swapped back to the stock EL84 and it's working again.

 

So... Do I just have a lemon here? Or is this still par for the course on these? I don't want to pop the top screw covers off the outside to remove the chassis to start checking voltages and everything because I assume that will void the warranty. (I don't want to void the warranty until I know this thing is OK).

 

Any ideas?

 

Thanks again.

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Yep. Tubes is tubes, and that particular Ruby tube's a lemon for sure. That'll happen occasionally. All the more reason to buy more than one tube at a time, and test each one for a couple hours. Do this as soon as you get 'em so you can find the duds and take 'em back.

 

Gil...

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FWIW, if you have a volt meter, check your AC voltage at the wall receptacle. If it's in the 120 to 125ACv range, you're amp will probably continue to eat power tubes on a regular basis. This is because it's built for 115vAC, and the higher wall voltage makes the power tube run hotter. And, because it was already biased hot to begin with, with the higher than expected wall voltage causes the amp to be biased way too hot for the excessive operating conditions it's dealing with.

 

If your wall voltage does indeed run high, you need to make a decision! Are you willing to swap out a few resistors to have your power tube last maybe a year or two, or would you rather just keep swapping tubes every month or two or three for the sake of not voiding the warranty? If you decide to do it yourself, you may even discover that you won't be needing that silly old warranty anymore anyway. [crying]

 

Gil...

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Hi Scott,

Are you still having running issues?

Were the Ruby tubes new?

What are you trying to achieve by changing tubes?

What are you using for a speaker and cabinet?

 

A speaker change will change the tonal voice of the sound. Tubes will change the gain structure. If I were you I wouldn't worry about the voltage in your home. That's just me.

 

"The answer is to use your ears. Most new guitar amplifiers like to see 117VAC to 120VAC. Most modern amps are wired for 120VAC power. Most homes these days show 119-121VAC coming out of the wall socket. Most stages might get up to 118VAC on a good day but will otherwise be lower, which can adversely affect your sound."

 

Quoted from this page. Variac - Why you should have one.

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He's not dealing with "most" guitar amps, he's got a VJr, which has well documented issues regarding higher wall voltage.

 

SEwatt.com has all the mods and reference material links you'll need to turn that VJr into a sweet tone machine. Besides, a few resistors and caps are far less expensive than a variac.

 

Gil...

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He's not dealing with "most" guitar amps' date=' he's got a VJr, which has well documented issues regarding higher wall voltage.

 

SEwatt.com has all the mods and reference material links you'll need to turn that VJr into a sweet tone machine. Besides, a few resistors and caps are far less expensive than a variac.

 

Gil...

[/quote']

 

Hi Gil,

Although I whole-heartedly admit to not knowing half of what you know about amp circuits, I find it hard to believe Epiphone continues to produce 100s of thousands of amps shipped all over the world with such a basic flaw. They're on their 3rd or 4th revision as well. Plugging an amp into the wall outlet of a standard house blows outputs tubes every 2 or 3 months. Wow. Shame on Epiphone if this is true. If it is true, a recall is in order.

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Thanks for the continued support on this.

 

Yes, the Ruby tube was new. It failed after about 45 minutes of use (30 minutes one day, 15 minutes the next).

 

I bought the amp from guitarcenter.com with money I made selling old tubes I found at an estate sale. I bought the amp just for the tube sound at a low price, and to tinker with. I've built several stomp boxes and was thining about building an AX84 amp, then thought I'd get this and mod it a bit to ease me into the world of tube amps.

 

I'm feeding this into a Jensen Mod 12, 50W 8ohm in a homemade cabinet (AX84 plans).

 

If I've got to mod it or buy a variac just to use it in my home, yes I'd be disappointed.

 

So, for now, I put the stock power tube back in it, and so far so good.

 

But, I was hoping I wouldn't have to troubleshoot this amp until AFTER I modded it, not before.

 

As for mods, I'd just like some flexibility, maybe some sort of tone and some sort of switchable gain. But, first, I'd really like to get ths thing working consistently. That shouldn't be too much to ask, should it?

 

If there is a mod that will cool the voltage down a bit so that I don't have to buy tubes every months, that would be good.

 

Thanks again.

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Well, keep in mind that the VJr is really just a $100 tube amp. Not my fault they're getting $149; but anyway, it's obviously not in Epi/Gibson's best interest to sell a dirt cheep amp that siphons off the sales of they're high-dollar models, whether it's by competing on general quality or the more subjective tone levels. It's just not gonna happen! But, for a $100 amp, the VJr is hard to beat as a really good starting point.

 

Also consider that many amp companies, including Fender and Marshall, intentionally run their power tubes above spec. They'll swear all day long it's for the tone, but the truth is that a tube running below maximum spec'd ratings can sound every bit as good, and possibly last the whole 5 or 10,000 hours or whatever it's rated for (when operated below max design center votage specs)! After the sale, Fender still wants to get their hands on more of your money, so they build amps that keep them in the business of selling you more tubes for it. I realize it doesn't make sense for Epiphone or Marshall to continue building amps that cook tubes since they aren't in the tube retail biz; but that seems to be just one of those odd mysteries of the music biz that can't be explained.

 

Fortunately, places like SEwatt exist for those willing to take the time to learn how to set themselves free of all that hoorah and seeking access to the kind of tone quality that you just can't otherwise get at these bargain basement prices.

 

Gil...

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