My Legacy blew up!!!
- Thread starter B2D
- Start date
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Skarekrough
Guest
Re: My Legacy blew up!!!
...this whole tale needs to end with the phrase "...and the replacement unit from Carvin showed up today and they threw in a few free shirts."
...this whole tale needs to end with the phrase "...and the replacement unit from Carvin showed up today and they threw in a few free shirts."
Luke Duke
PRSlustologist
Re: My Legacy blew up!!!
+1
The more I think about it the more the 1 year warranty bothers me. You pay for a good tube amp you want to know somebody has got your back.
Luke
+1
The more I think about it the more the 1 year warranty bothers me. You pay for a good tube amp you want to know somebody has got your back.
Luke
Re: My Legacy blew up!!!
It looks like R75 is one of the burnt resistors on the output tube board. I can't make out the other one but the only resistor on that board that ends in an "8" is R78.
R75 is the grid stopper on the signal grid for V9. This applies the bias and the drive signal to the tube. For this grid resistor to draw enough current to smoke it, something must be wrong with V9 - the grid inside the tube would have to make contact with some other part inside the tube. But once it goes, the tube would lose bias and conduct to saturation. That's probably what heated up the output transformer - they will do that once current on the two primaries becomes mismatched. Probably what blew the fuse.
R78 - this is one side of the hum balance control for the AC heaters. The other side is R79 which is adjustable. If this is what the resistor is, I can't come up with any reason for it to smoke.
It would be interesting to know what those resistors on the preamp board are. Nothing around the circuit of V1 with 2 resistors seems like it could have been involved. But there are some power supply, including the bias circuit that look to be on that same board.
Interesting though...
Edit: forgot to add the link to the schematic if anyone is interested:
http://www.carvinmuseum.com/pdf/amps/VL100 & VL212 Legacy Amp.pdf
It looks like R75 is one of the burnt resistors on the output tube board. I can't make out the other one but the only resistor on that board that ends in an "8" is R78.
R75 is the grid stopper on the signal grid for V9. This applies the bias and the drive signal to the tube. For this grid resistor to draw enough current to smoke it, something must be wrong with V9 - the grid inside the tube would have to make contact with some other part inside the tube. But once it goes, the tube would lose bias and conduct to saturation. That's probably what heated up the output transformer - they will do that once current on the two primaries becomes mismatched. Probably what blew the fuse.
R78 - this is one side of the hum balance control for the AC heaters. The other side is R79 which is adjustable. If this is what the resistor is, I can't come up with any reason for it to smoke.
It would be interesting to know what those resistors on the preamp board are. Nothing around the circuit of V1 with 2 resistors seems like it could have been involved. But there are some power supply, including the bias circuit that look to be on that same board.
Interesting though...
Edit: forgot to add the link to the schematic if anyone is interested:
http://www.carvinmuseum.com/pdf/amps/VL100 & VL212 Legacy Amp.pdf
skyydogg01
Active member
Re: My Legacy blew up!!!
dang bro. that sucks. I hope everything works out for you.
just get a mesa stilleto ace and be done with it ...
dang bro. that sucks. I hope everything works out for you.
just get a mesa stilleto ace and be done with it ...
J Moose
New member
Re: My Legacy blew up!!!
WOW!!!
The PCB is melted!
Suckage.
Resistors are passive devices that RARELY fail on their own. Something else would have to go south and be way outta whack for them to burn up like that.
Chances are good that it wasn't your power soak that did this.
A capacitor, bridge rectifier, arcing tube or some other major component failing and taking several other things along for the ride would be a much safer bet.
If there were huge burn marks around the power tubes/output tranny or other parts of the output stage would be toasted. I'd say that roughly 90% of the time I hear of someones amp blowing up with a soak it's because they weren't using the soak correctly...wimpy speaker cables, impedance mismatches etc. down to no load at all, like one guy who tried to use a Hot Plate with his Ectasy for recording and jammed the speaker level out (of the soak) into a DI box!
:laughing:
Rest assured...in the five years I've been running an AC30 & '61 Bandmaster (among others) with a Marshall Power Break I've (knock on wood!) never had a problem that was related to the soak.
What are the tube sockets attached to? Are they mounted on the chassis and wired down to the PCB or are they mounted directly to the PCB?
The traces for the V1 socket were vaporized! What's the unidentifiable 'blobified' component to the left of that socket? Or I guess the better question would be, what WAS it?!
Either way, the PCB with the preamp tubes is most likely gonna have to be replaced. It's not unrepairable, but hopefully it's not gonna be half the cost of the amp either!
Here's to hoping they take care you on it!
And look for something else besides a Carvin would 'ya? Get a Rivera or something reliable!
At the very least, going to a smaller 2x10 or 2x12 open back cab will help with some of your extreme volume problems.
WOW!!!
The PCB is melted!
Suckage.
Resistors are passive devices that RARELY fail on their own. Something else would have to go south and be way outta whack for them to burn up like that.
Chances are good that it wasn't your power soak that did this.
A capacitor, bridge rectifier, arcing tube or some other major component failing and taking several other things along for the ride would be a much safer bet.
If there were huge burn marks around the power tubes/output tranny or other parts of the output stage would be toasted. I'd say that roughly 90% of the time I hear of someones amp blowing up with a soak it's because they weren't using the soak correctly...wimpy speaker cables, impedance mismatches etc. down to no load at all, like one guy who tried to use a Hot Plate with his Ectasy for recording and jammed the speaker level out (of the soak) into a DI box!
:laughing:
Rest assured...in the five years I've been running an AC30 & '61 Bandmaster (among others) with a Marshall Power Break I've (knock on wood!) never had a problem that was related to the soak.
What are the tube sockets attached to? Are they mounted on the chassis and wired down to the PCB or are they mounted directly to the PCB?
The traces for the V1 socket were vaporized! What's the unidentifiable 'blobified' component to the left of that socket? Or I guess the better question would be, what WAS it?!
Either way, the PCB with the preamp tubes is most likely gonna have to be replaced. It's not unrepairable, but hopefully it's not gonna be half the cost of the amp either!
Here's to hoping they take care you on it!
And look for something else besides a Carvin would 'ya? Get a Rivera or something reliable!
At the very least, going to a smaller 2x10 or 2x12 open back cab will help with some of your extreme volume problems.
kevlar3000
Bullet Proof Toneologist
Re: My Legacy blew up!!!
That really sucks!! Very sorry to hear it... I can say in 4 yrs of daily use My Weber Mass has not blown up a single amp. I have 17 amps now, 15 are older than 1972. I would look at another cause for that failure 1st. Hope you can get her straightened out!!
That really sucks!! Very sorry to hear it... I can say in 4 yrs of daily use My Weber Mass has not blown up a single amp. I have 17 amps now, 15 are older than 1972. I would look at another cause for that failure 1st. Hope you can get her straightened out!!
Jeff Seal
New member
Re: My Legacy blew up!!!
Attenuators...... (ya might wanna get a snack and something to drink for this read!)
Traditionally, attenuators were nothing more than resistors wired to "dissipate" power via heat, thus lessening the amount available to the speakers. This unfortunately has a major flaw inherently.... while an 8 ohm resistor has the same impedance (more or less) as an 8 ohm speaker, they are nowhere near the same. The resistor has a direct path through it, and can only dissipate power via heat. The 8 ohm coil in the speaker also has a direct path, but dissipates it by physically moving the cone to which it's attached. Knowing that current will always follow the path of least resistance, current is more likely to move through the 8 ohm resistor than it will move through the 8 ohm coil, because that coil is required to physically move something (which requires more current) than the resistor, which is just converting it to heat.
In case you're not aware, speakers do generate voltage when the cone is moved. If you don't believe me try it!! Hook up a volt meter to a speaker and push the cone in a few times.... you wont get much.... Speakers are incredibly inefficient, as are most things that convert electicity to motion. Simple resistors are incredibly efficient by contrast and although the two may have the same impedance, they're nowhere near the same. As the coil in the speaker moves outward, a negative state of current will exist on the negative terminal thus pulling current from the source, conversely, it will push current in a positive direction as the cone moves inward... (basically that's how a speaker works) The current is forever changing direction as it follows the signal, and minimal heat is created as the power is being translated into physical movement. Speakers and Tranformers PASS signal's they aren't designed to hold it unless there's no other place to go (and then they burn!) The plates in power tubes create energy that HAS to be directed somewhere. It will see the primary windings as a "load resistor" if, the signal has no other place to go and thus heat it up until it fries.
For those of you who are rather inqusitive by nature, (and just happen to have an ohmmeter) check this out! Unplug your amp from the wall (kinda important!!) turn the amp power switch on and take a resistance reading between the spade terminals.... you're probably reading around 3 ohms.
If you were to plug a 3 ohm resistor straight into the wall, it would either flame up or trip the breaker (DO NOT try this btw!) So what makes this 3 ohm load not burn up????.... simple, it's converting it into a magnetic field which won't draw any current unless the secondary side demands it... If that secondary side is severely mismatched or has "extraneous" unresolved power loads.... bad things are gonna happen!
Think about it this way, if you've ever ridden a 10-speed bicycle, you know how much effort it takes to start off in 10th gear and also how hard it is to go uphill. First or second gear is great for starting off and going hard uphill, so you choose you gear selection accordingly. This basically is the same as the impedance selector switch on a tube amp... your matching the "load" to best suit the working conditions for optimum results... make sense so far?
Now you're going to introduce your "attenuator", which in the case of the bicycle is the same as partially applying the brake all the time.. you've limited your speed but it's much harder on your power source.. which in the case of the bicycle is the rider, in the amp it's the output section. The output tubes are not particularly used to having electrons "back up" inside the tube itself, and most output transformers will start to heat up in protest. So, eventually the plate voltage will find the next best path to go to. The grid is below plate potential and current is (again) always looking for the least path of resistance. Since current flows from negative to positive, the first place the HV (plate) is going to arc to is the heater 99.9%. As soon as that happens the grid feed resistors will fry (the two in the pic by the output tubes!.... standard issue failure!) because they're trying to feed an "insatiable" amount of current being imposed on the grid. Usually, the "hum" balance resistors will fry as the heater circuit is subjected to 100X the amount of voltage it's used to seeing. The HV is looking for ground, not 6.3v... I would venture to guess those are the two burnt resistors by V1.... (hold on, more to come!)
Attenuators...... (ya might wanna get a snack and something to drink for this read!)
Traditionally, attenuators were nothing more than resistors wired to "dissipate" power via heat, thus lessening the amount available to the speakers. This unfortunately has a major flaw inherently.... while an 8 ohm resistor has the same impedance (more or less) as an 8 ohm speaker, they are nowhere near the same. The resistor has a direct path through it, and can only dissipate power via heat. The 8 ohm coil in the speaker also has a direct path, but dissipates it by physically moving the cone to which it's attached. Knowing that current will always follow the path of least resistance, current is more likely to move through the 8 ohm resistor than it will move through the 8 ohm coil, because that coil is required to physically move something (which requires more current) than the resistor, which is just converting it to heat.
In case you're not aware, speakers do generate voltage when the cone is moved. If you don't believe me try it!! Hook up a volt meter to a speaker and push the cone in a few times.... you wont get much.... Speakers are incredibly inefficient, as are most things that convert electicity to motion. Simple resistors are incredibly efficient by contrast and although the two may have the same impedance, they're nowhere near the same. As the coil in the speaker moves outward, a negative state of current will exist on the negative terminal thus pulling current from the source, conversely, it will push current in a positive direction as the cone moves inward... (basically that's how a speaker works) The current is forever changing direction as it follows the signal, and minimal heat is created as the power is being translated into physical movement. Speakers and Tranformers PASS signal's they aren't designed to hold it unless there's no other place to go (and then they burn!) The plates in power tubes create energy that HAS to be directed somewhere. It will see the primary windings as a "load resistor" if, the signal has no other place to go and thus heat it up until it fries.
For those of you who are rather inqusitive by nature, (and just happen to have an ohmmeter) check this out! Unplug your amp from the wall (kinda important!!) turn the amp power switch on and take a resistance reading between the spade terminals.... you're probably reading around 3 ohms.
If you were to plug a 3 ohm resistor straight into the wall, it would either flame up or trip the breaker (DO NOT try this btw!) So what makes this 3 ohm load not burn up????.... simple, it's converting it into a magnetic field which won't draw any current unless the secondary side demands it... If that secondary side is severely mismatched or has "extraneous" unresolved power loads.... bad things are gonna happen!
Think about it this way, if you've ever ridden a 10-speed bicycle, you know how much effort it takes to start off in 10th gear and also how hard it is to go uphill. First or second gear is great for starting off and going hard uphill, so you choose you gear selection accordingly. This basically is the same as the impedance selector switch on a tube amp... your matching the "load" to best suit the working conditions for optimum results... make sense so far?
Now you're going to introduce your "attenuator", which in the case of the bicycle is the same as partially applying the brake all the time.. you've limited your speed but it's much harder on your power source.. which in the case of the bicycle is the rider, in the amp it's the output section. The output tubes are not particularly used to having electrons "back up" inside the tube itself, and most output transformers will start to heat up in protest. So, eventually the plate voltage will find the next best path to go to. The grid is below plate potential and current is (again) always looking for the least path of resistance. Since current flows from negative to positive, the first place the HV (plate) is going to arc to is the heater 99.9%. As soon as that happens the grid feed resistors will fry (the two in the pic by the output tubes!.... standard issue failure!) because they're trying to feed an "insatiable" amount of current being imposed on the grid. Usually, the "hum" balance resistors will fry as the heater circuit is subjected to 100X the amount of voltage it's used to seeing. The HV is looking for ground, not 6.3v... I would venture to guess those are the two burnt resistors by V1.... (hold on, more to come!)
Jeff Seal
New member
Re: My Legacy blew up!!!
When B2D said his OT was too hot to touch, he was exactly right.... too much unresolved power getting backed up!!
I'm not a big fan of attenuators and have seen many an amp meet it's demise because of them. Unless a device converts energy to a passive load, it's merely just killing it off and the amp in the process!!!
I have to admit, I really haven't kept up with "attenuator" technology, but I just look at it this way..... If you think you're gonna cram an elephant into a small box without something bad happening, you might want to think again!
Just my lowly .02
Oh, since I know it's already coming, something else to think about... for those of you who are currently using one, everything works until it doesn't work...... I've been successfully smoking for 30 yrs now, why should I stop now???
geez, that took a long time to type....
hope it helped more than confused!
Jeff Seal
When B2D said his OT was too hot to touch, he was exactly right.... too much unresolved power getting backed up!!
I'm not a big fan of attenuators and have seen many an amp meet it's demise because of them. Unless a device converts energy to a passive load, it's merely just killing it off and the amp in the process!!!
I have to admit, I really haven't kept up with "attenuator" technology, but I just look at it this way..... If you think you're gonna cram an elephant into a small box without something bad happening, you might want to think again!
Just my lowly .02
Oh, since I know it's already coming, something else to think about... for those of you who are currently using one, everything works until it doesn't work...... I've been successfully smoking for 30 yrs now, why should I stop now???
geez, that took a long time to type....
hope it helped more than confused!
Jeff Seal
Virtual Kevorkian
New member
Re: My Legacy blew up!!!
Damn, that kills my desire for an Attenuator.
Jeff, do you know if the 'speaker motor' type Attenuators that Weber offer would provide the same kind of movement a speaker does, and save the amp?
http://www.tedweber.com/atten.htm
Midway down the page.
Damn, that kills my desire for an Attenuator.
Jeff, do you know if the 'speaker motor' type Attenuators that Weber offer would provide the same kind of movement a speaker does, and save the amp?
http://www.tedweber.com/atten.htm
Midway down the page.
Re: My Legacy blew up!!!
Jeff... thank you so much. I was really hoping you'd pop in on this one but wasn't counting on it.
Looks like I'm never using an attenuator again. If that wasn't directly the cause I bet it contributed to it...
So Jeff... got any way to turn a 50 or 100 watt EL34 amp into a 30-watter?
Jeff... thank you so much. I was really hoping you'd pop in on this one but wasn't counting on it.
Looks like I'm never using an attenuator again. If that wasn't directly the cause I bet it contributed to it...
So Jeff... got any way to turn a 50 or 100 watt EL34 amp into a 30-watter?
3
34029324079
Guest
Re: My Legacy blew up!!!
yikes! sorry to hear that bit about the attenuator - sux that the amp got fried
yikes! sorry to hear that bit about the attenuator - sux that the amp got fried
J Moose
New member
Re: My Legacy blew up!!!
Ok Jeff...
I'm offically more confused now then before! :dunno:
At least slightly... I'm not a huge tech head.
Right on. I'm with you...
Yup.
Ok. This is where you lost me.
If our 8 ohm resistor in the attenuator has "a direct path through it" as you said...and some of that RMS energy from the head is being disipated to heat, then how exactly, are things getting "backed up" to the point that the power tubes and/or output tranny or would become so unhappy that they burn up?
Granted, I realize that older designs like the Scholz soaks are UBER dangerous and I know they've been responsible for more then a few toasted amps, but things like the Marshall break & THD plates have a fan & light bulb that respectively spin & glow like Chernobal when the player is wailin' away and I've never seen someone toast an amp with one of those unless it was hooked up incorrectly.
Again...I'm no tech...
Ok Jeff...
I'm offically more confused now then before! :dunno:
At least slightly... I'm not a huge tech head.
Right on. I'm with you...
Yup.
Ok. This is where you lost me.
If our 8 ohm resistor in the attenuator has "a direct path through it" as you said...and some of that RMS energy from the head is being disipated to heat, then how exactly, are things getting "backed up" to the point that the power tubes and/or output tranny or would become so unhappy that they burn up?
Granted, I realize that older designs like the Scholz soaks are UBER dangerous and I know they've been responsible for more then a few toasted amps, but things like the Marshall break & THD plates have a fan & light bulb that respectively spin & glow like Chernobal when the player is wailin' away and I've never seen someone toast an amp with one of those unless it was hooked up incorrectly.
Again...I'm no tech...
Last edited:
Re: My Legacy blew up!!!
I'm using a Dr. Z/Trainwreck Air Brake, which while being simple is not a bad peice by any means.
I'm using a Dr. Z/Trainwreck Air Brake, which while being simple is not a bad peice by any means.
J Moose
New member
Re: My Legacy blew up!!!
I think the Z Airbrakes sound really good. Better then my Marshall anyway. I wanted one but couldn't find one in time & then came across a smokin' deal on the used power break so that was that.
You should be pretty safe with the airbrake I'd think...
BTW, were you running the Carvin in 100 watt or 50 watt mode? Does it have that option?
I think the Z Airbrakes sound really good. Better then my Marshall anyway. I wanted one but couldn't find one in time & then came across a smokin' deal on the used power break so that was that.
You should be pretty safe with the airbrake I'd think...
BTW, were you running the Carvin in 100 watt or 50 watt mode? Does it have that option?
