Helpful ReplyCarvin XV-212

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ReubDot
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2014/12/17 18:26:43 (permalink)

Carvin XV-212

I've owned my Carvin amp since '85, it's always worked fine.  One day while I was playing guitar, while at the same time my wife was vacuuming the carpet in the same room.  I heard a BB pellet go up the vacuum tube, and my amp within a few seconds went dead. There was no smell, no noise when it stopped amplifying.  The power light was still on, the power fuse and the speaker fuse were good. The tubes all were not glowing, the larger transformer was cold, but the smaller transformer was barely warm, with a faint hum.  No sign of any burn smell or visual damage could be seen on the circuit board.  I tested the speakers, they are both good.  All controls are DOA, and all tubes were changed last year. I only use my amp at home, and don't even turn the volume to (1) CAN ANYONE HELP-I can do my own repair if I knew what part to change.  I thought that someone out there might of had a similar problem, any advice would be greatly appreciated.
#1
cowboydan
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Re: Carvin XV-212 2014/12/17 18:59:37 (permalink)
Maybe just take the tubes out one by one and spray the sockets with contact spray and put them back in again. Maybe just a corroded connection.
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cowboydan
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Re: Carvin XV-212 2014/12/17 19:00:24 (permalink)
Otherwise your input tube went out.
 
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ReubDot
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Re: Carvin XV-212 2014/12/17 19:16:44 (permalink)
I don't know much about amps, I've been trying to find someone that could test the tubes for me.
Can one tube cause everything to stop working? Which tube is the input tube, the (3) small tubes, or the (4) large tubes?
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Paul P
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Re: Carvin XV-212 2014/12/17 19:48:32 (permalink)
 
Are there any solid-state circuits in your tube amp ?
 
If so, something might have gotten zapped by a static electricity discharge from the vacuum cleaning.
Did your wife touch you or your amp while cleaning ?  I once had so much static electricity building up on my vacuum cleaner's tube/hose that I wrapped it in wire and grounded it.
 
You sure that was a BB pellet and not a zap (or your circuits popping) ?
 
I doubt a vacuum tube (the ones in the amp) would be affected by a static electricity discharge, the parts are substantial metal.  A solid-state circuit board would have to be completely replaced, I imagine, and it might be hard to find one for an '85.
 
 

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ReubDot
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Re: Carvin XV-212 2014/12/17 20:31:10 (permalink)
Yeh, I was filling a pouch with BB's that week, right by my office chair I must have dropped one.  And being a new carpet, I guess it would have a lot of static.  My wife was on the other side of my desk, and I was sitting down.  When it stopped working, it first got lower in volume and distorted.  I turned it off, checked a few things on it, then turned it back on, then nothing.  Yeh, it's a circuit board with, ceramic capacitors, resisters, diodes, condensers, etc., on a printed circuit. 
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Paul P
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Re: Carvin XV-212 2014/12/17 21:53:39 (permalink) ☄ Helpfulby ReubDot 2014/12/18 10:57:45
 
Could be any number of things I suppose, maybe a capacitor dying.  That's a pretty old amp, at least 30 years old.  Electrolytic capacitors have a non-infinite lifespan and old amps usually have to have them replaced sooner or later.
 
The vacuum cleaner may have had nothing to do with, just an odd coincidence.
 
 

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ampfixer
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Re: Carvin XV-212 2014/12/18 03:29:07 (permalink) ☄ Helpfulby ReubDot 2014/12/18 10:58:14
You said that the tubes were not glowing. This means the filament supply voltage is missing. You have a problem in your power supply. It could be an internal fuse on the filament supply or something worse. This will have to be fixed by a tech.
 
There is a very remote chance that all the tubes have their filaments wired in series. If one tube has a bad filament it could shut down all the tubes in the string. 
 
Most likely scenario is that you had a shorted filament in one of the tubes and it blew the filament supply fuse.

Regards, John 
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#8
ReubDot
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Re: Carvin XV-212 2014/12/18 11:17:32 (permalink)
I also think it's a capacitor, I'm waiting for a tech from my area to get back to me.
He gets $80 an hour, I'm retired and only play as a hobby. $80 is the least it will cost,
it could cost me hundreds before I'm done. 
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ReubDot
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Re: Carvin XV-212 2014/12/18 11:25:32 (permalink)
Are the capacitors the large blue and round component with silver ends, with a wire on each end.
About 2" long, and around 3/4" in diameter?
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Karyn
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Re: Carvin XV-212 2014/12/18 11:47:19 (permalink)
Yes,  but I'm with ampfixer on this one.  You said the tubes were all not glowing.  If they're not glowing, they won't work.
 
It's a very simple circuit, the mains power transformer will have a 5 - 6 volt output that feeds all of the tube heaters, maybe with a fuse inline, maybe not.  If the tubes aren't lit, there's your problem.

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ReubDot
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Re: Carvin XV-212 2014/12/18 11:58:11 (permalink)
As I mentioned in one of my post, the smaller transformer with about (7) wires coming out from it was just a little warm with a very low hum.  The larger transformer was ice cold, it had (3) wires.  Is the larger transformer the output transformer?  And I searched the web to try to find out if I could identify an internal fuse. I couldn't find any info on that.
Even if something was burned out in the circuit leading to the tubes, you're saying the tubes will still be glowing?
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ReubDot
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Re: Carvin XV-212 2014/12/18 12:02:47 (permalink)
Even if something was burned out in the circuit leading to the tubes, you're saying the tubes will still be glowing?
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Karyn
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Re: Carvin XV-212 2014/12/18 12:06:58 (permalink)
As long as it wasn't part of the tube heater supply, the tubes should still be glowing.
 
Be careful putting your fingers in there to see if things are warm. 

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ReubDot
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Re: Carvin XV-212 2014/12/18 12:10:08 (permalink)
I've had my fingers in there already, but only touching parts that were not metal, except the main body of the transformers.  The smaller transformer is the only part that was not cold.
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Karyn
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Re: Carvin XV-212 2014/12/18 12:16:18 (permalink)
 
Take a look at this circuit diagram for my tube amp.
 
Even if you have no clue what you're looking at it's clear, at the bottom of the drawing, how all the tube heaters are totally separate from the rest of the amp circuit.  You should also be able to see that the Power Light on mine is shown at the end of that chain.  So if the power light is on, there IS power to the tube heaters.
 
However, the power light could be connected anywhere,  if it were first in the chain then any break in the wires after that would turn off the tubes and the amp would be dead, but the power light would still be on.
 
 
Edit:  The power light doesn't have to be part of the tube heater circuit at all....   it just happens to be in my amp.

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The Maillard Reaction
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Re: Carvin XV-212 2014/12/18 12:32:13 (permalink)
For safety's sake. Get someone with some experience poking around a tube amp to help you.


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ReubDot
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Re: Carvin XV-212 2014/12/18 12:36:20 (permalink)
You're right, I'm waiting for a return call today from a tech.
I'm 68, don't need to die from amp voltage.
 
Thanks Reuben
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Re: Carvin XV-212 2014/12/18 12:38:38 (permalink)
Thanks,
There are too many things that can go wrong in a circuit.  I just hope it's not a transformer or the circuit board. I'll just take it to a tech, and hope that it's not too costly!
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Re: Carvin XV-212 2014/12/18 12:40:44 (permalink)
If the person knows guitar amps this should be a quick diagnosis and perhaps the repair work can be done at less than $80 / hr.

Wishing you the best of luck!


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ReubDot
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Re: Carvin XV-212 2014/12/18 12:47:26 (permalink)
The tech has over 35 years experience, but $80 in the minimum charge per hour, with a one hour minimum.  That is OK with me, but if they bill me for (2) hours, I would say they were taking advantage.
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Re: Carvin XV-212 2014/12/18 14:25:58 (permalink)
I have the XV 212S that I bought in 1989. I am sorry to hear of your situation but definitely agree with not poking around in that amp with power to it. If a capacitor does charge, it can mean bad news quickly.
 
http://www.carvinservice.com/crg/manuals/x-amp.pdf is a link to the wiring diagram for that amp series.
 
It may also be worth contacting Carvin directly regarding authorized technicians in your area. I contacted them several months ago about mine and they responded to me the same day.

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Karyn
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Re: Carvin XV-212 2014/12/18 15:22:18 (permalink)
Looking at the circuit diagram, the heaters are shown the same as in my Vox.  The good news, it limits the fault possibilities to just one of three things.
1)broken track on the PCB removing power from the heaters.
2)broken connection between transformer and PCB, where the wires connect to the PCB (the two brown wires connected to H1-4 and H1-5)
3)burnt out transformer.
 
1)is easy to fix.  2)is even easier to fix (and the most likely) 3)is the most expensive, but not difficult.
 
To reiterate what Mike said,  DO NOT stick your fingers anywhere inside unless you really know what you're doing.

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The Maillard Reaction
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Re: Carvin XV-212 2014/12/18 15:33:57 (permalink)
I just looked at the schematic. That is one complicated tube amp circuit.
 
The tone stack and reverb loop is all solid state, and there are some FETs and a couple 4558 I.C. op amps in the tube preamp section.
 
The tube heaters are wired in parallel.
 
If the diagnosis isn't made in the first 10 minutes than there is no telling how long it might take. It sure will be helpful for time savings if the tech knows this particular amp series.


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Karyn
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Re: Carvin XV-212 2014/12/18 18:05:13 (permalink)
ReubDot
The power light was still on, the power fuse and the speaker fuse were good. The tubes all were not glowing, the larger transformer was cold, but the smaller transformer was barely warm, with a faint hum. 

ReubDot
  When it stopped working, it first got lower in volume and distorted.  I turned it off, checked a few things on it, then turned it back on, then nothing. 

That really sounds like the 6v secondary winding breaking down.  It should be really easy for your tech guy to check for voltage from it.

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Paul P
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Re: Carvin XV-212 2014/12/18 18:15:54 (permalink)
 
Hey, don't go putting your hands in there.  Tube amps have supplies in the hundreds of volts, around 400 is common.  At that level, you won't be able to disconnect yourself if you touch the wrong thing.
 
When I work on the innards of my amp, I wear rubber boots standing on a rubber mat, have rubber gloves and, importantly, always keep one arm/hand behind my back.  This is just standard procedure when working with tubes.  Well at least when they're plugged in or until I've made sure the power supply caps are properly drained.
 
Not all amps will automatically bleed the big power supply caps and those can keep their charge (of 400v) indefinitely.
 
Sorry, should have warned you not to go trying to fix things yourself.  You could be dead right now.
 

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