Tube replacement hep
- Thread starter Clint 55
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The Standby switch is a fallacy, in fact, I just released a video about that yesterday.
It is a thing Fender did, and others just copied it. It has since become a ubiquitous " feature ", that really doesn't have much merit to it.
Cathode striping is an old wives' tale and is only relevant to tubes with over 1kv on the plates. Cathode poisoning is also another old wives' tale that happens when you leave a tube on standby for prolonged periods of time.
The only thing I can say that is good about a standby switch is that it does allow you to unplug a speaker while the amp is on. It makes some aspects of testing the amp a little easier, but for normal operation, it is just an expensive addition that does nothing. A good switch can cost $6 to $10, and then the labor to install it, I guess if amp companies really wanted to save a few bucks this is where to start.
I will go out on a limb and say that ANY amp with a tube rectifier does not need one at all. There are some amp designs that can benefit from having one, but there are other much less expensive ways to eliminate the standby switch. The problem isn't the standby switch itself, but the way it is implemented. The implementation is what often makes using the standby switch much worse than not having it at all.
For those that care:
As for how an amp fails and why is hard to say without a post-mortem. PCB amps have proven to be one of the more difficult to repair when anomalous things happen. Conductive PCB's from getting too hot, to traces that fail. Even old Fender's eyelet boards that go conductive as the wax dries out and moisture wicks in can cause all kinds of weird things. There is no one thing to blame, and standby switches and their misuse are not to blame for most of the issues.
Standby switches are just not really needed, the problems they cause are often just related to tube life. As in, the use of the standby switch can reduce the life of tubes in certain circumstances. Not all, just some. As mentioned, some amp designs do benefit from having one, but also as mentioned, there are cheaper, better ways to eliminate the need for one altogether.
It is a thing Fender did, and others just copied it. It has since become a ubiquitous " feature ", that really doesn't have much merit to it.
Cathode striping is an old wives' tale and is only relevant to tubes with over 1kv on the plates. Cathode poisoning is also another old wives' tale that happens when you leave a tube on standby for prolonged periods of time.
The only thing I can say that is good about a standby switch is that it does allow you to unplug a speaker while the amp is on. It makes some aspects of testing the amp a little easier, but for normal operation, it is just an expensive addition that does nothing. A good switch can cost $6 to $10, and then the labor to install it, I guess if amp companies really wanted to save a few bucks this is where to start.
I will go out on a limb and say that ANY amp with a tube rectifier does not need one at all. There are some amp designs that can benefit from having one, but there are other much less expensive ways to eliminate the standby switch. The problem isn't the standby switch itself, but the way it is implemented. The implementation is what often makes using the standby switch much worse than not having it at all.
For those that care:
As for how an amp fails and why is hard to say without a post-mortem. PCB amps have proven to be one of the more difficult to repair when anomalous things happen. Conductive PCB's from getting too hot, to traces that fail. Even old Fender's eyelet boards that go conductive as the wax dries out and moisture wicks in can cause all kinds of weird things. There is no one thing to blame, and standby switches and their misuse are not to blame for most of the issues.
Standby switches are just not really needed, the problems they cause are often just related to tube life. As in, the use of the standby switch can reduce the life of tubes in certain circumstances. Not all, just some. As mentioned, some amp designs do benefit from having one, but also as mentioned, there are cheaper, better ways to eliminate the need for one altogether.
JMP/HBE
Well-known member
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beaubrummels
Well-known member
I don't have an electronics degree, so I can't dispute with someone who has that knowledge. But these are just my 2 cents from what I know and from my experiences.
I haven't heard of a drained cap as being equal to ground before. My understanding is as soon as signal hits a cap, it starts filling up and the cap appears as a load.
I haven't seen a tube rectifier arc before, either in an amp without a standby or in an amp with the standby open. I'll have to pay closer attention though and see if I notice it.
I have a AC30 without a standby, and I have powered on some of my other amps without the standby and in all those cases it sends a powerful loud spike into the speakers that is not good for speakers. I would posit that, given a GZ34 is $20 and 2 x 12" Celestion Blues are $478, I'd rather the rectifier go than the speakers. Sure, bad for the amp for a second or two, but I don't think it will require further servicing of the amp at greater expense. But I'm open to be convinced otherwise. I guess school me on what happens when the rectifier tube goes and why those repairs are more than the speakers.
I haven't had any problems with JJ tubes in any amp I own. I haven't had one go bad yet in 20 years. I can't discount others who have had bad experiences, but I would have expected, having a half dozen amps with JJ's, I should have hit the problem by now but I haven't.
I'm not the most learned amp person, I'm not a repair tech or a builder. But in my practical experience, I see benefit in using the standby for a few seconds initially if only to preserve my speakers.
I haven't heard of a drained cap as being equal to ground before. My understanding is as soon as signal hits a cap, it starts filling up and the cap appears as a load.
I haven't seen a tube rectifier arc before, either in an amp without a standby or in an amp with the standby open. I'll have to pay closer attention though and see if I notice it.
I have a AC30 without a standby, and I have powered on some of my other amps without the standby and in all those cases it sends a powerful loud spike into the speakers that is not good for speakers. I would posit that, given a GZ34 is $20 and 2 x 12" Celestion Blues are $478, I'd rather the rectifier go than the speakers. Sure, bad for the amp for a second or two, but I don't think it will require further servicing of the amp at greater expense. But I'm open to be convinced otherwise. I guess school me on what happens when the rectifier tube goes and why those repairs are more than the speakers.
I haven't had any problems with JJ tubes in any amp I own. I haven't had one go bad yet in 20 years. I can't discount others who have had bad experiences, but I would have expected, having a half dozen amps with JJ's, I should have hit the problem by now but I haven't.
I'm not the most learned amp person, I'm not a repair tech or a builder. But in my practical experience, I see benefit in using the standby for a few seconds initially if only to preserve my speakers.
JMP/HBE
Well-known member
Pin # 1 to ground is what most amp techs do before ever touching anything on an amp.
Any amp any size any make has the potential for a lethal discharge with or w/o a standby.
Anyone who is cocky enough to think otherwise best have their end of life issues prepaid.
beaubrummels
Well-known member
I was responding to the standby video, and strictly from an end-user usage standpoint, rather than a repair standpoint.
Powering off and draining the filter caps is the first order of business before reaching inside an amp, AFAIK. But I don't plan to become a working tech, only deal with it if I absolutely have to, e.g. there is no one to take on servicing the amp. There is plenty of information available on the safe way to service a tube amp.
Powering off and draining the filter caps is the first order of business before reaching inside an amp, AFAIK. But I don't plan to become a working tech, only deal with it if I absolutely have to, e.g. there is no one to take on servicing the amp. There is plenty of information available on the safe way to service a tube amp.
Gtrjunior
New member
Yeah, you have a blown tube. The tube on the left with the white residue at the top has lost its vacuum seal.
Replace the set and bias the amp and you should be gtg.
How you get a thump from turning a tube amp on with the standby on is beyond me. The filaments haven't had a chance to warm up, so the tubes cannot conduct to produce sound, especially in an amp that is tube rectified ( no voltage is passing through the rectifier when the filaments are cold ).
I also doubt that a thump to the speakers will be their death. The speakers have a higher wattage rating than most amps produce, so how can they burn out in a split-second thump caused by a spike in an amp that can only produce X watts? I bet that is a rare form of death.
In the video, I mention that if the tube rectifier goes into meltdown, it can take out the power transformer, the tubes, and the output transformer. Pretty much the whole amp! While that may not cost $400 - $500 to replace the parts, the labor to replace them will. Never cheat the labor, that's my number one rule.
I'm only saying that there are MANY possibilities, and the reason why is subject to a postmortem. Blown speakers are rarer than tubes that fail. Rectifier tubes are pretty robust and last a fairly long time. The standby method that I prescribe is problematic, has been that way since forever ago now, and the failure rate is still pretty low in the grand scheme of things, but it isn't something to discount. Amps that have solid-state rectifiers are not bothered by the standby switch, only certain tubes in the amp that are affected by having large amounts of voltage on their plate and grid ( like cathode followers, which exist in MANY amp ) are. Just pointing out possibilities, no wrongs, no rights.
I also doubt that a thump to the speakers will be their death. The speakers have a higher wattage rating than most amps produce, so how can they burn out in a split-second thump caused by a spike in an amp that can only produce X watts? I bet that is a rare form of death.
In the video, I mention that if the tube rectifier goes into meltdown, it can take out the power transformer, the tubes, and the output transformer. Pretty much the whole amp! While that may not cost $400 - $500 to replace the parts, the labor to replace them will. Never cheat the labor, that's my number one rule.
I'm only saying that there are MANY possibilities, and the reason why is subject to a postmortem. Blown speakers are rarer than tubes that fail. Rectifier tubes are pretty robust and last a fairly long time. The standby method that I prescribe is problematic, has been that way since forever ago now, and the failure rate is still pretty low in the grand scheme of things, but it isn't something to discount. Amps that have solid-state rectifiers are not bothered by the standby switch, only certain tubes in the amp that are affected by having large amounts of voltage on their plate and grid ( like cathode followers, which exist in MANY amp ) are. Just pointing out possibilities, no wrongs, no rights.
Rex_Rocker
Well-known member
I actually find the JJ ECC83S's are super reliable. I don't like how they sound, but I've never had one fail on me. They're by far the least microphonic preamp tubes I've tried too.
For JJ power tubes, I've actually never had a set not fail on me, LOL. Don't like how they sound either, personally. I've not tried a huge variety, TBH, but I've had EL84's, 6L6's, 6V6S's and E34L's. Actually, I take that back. The 6V6S's do sound nice, but mine blew.
I hate to be negative, but even Chinese power tubes have been more reliable in my case. And nicer-sounding. But to be fair, I love Chinese tubes, LOL. Too bad they're not making them anymore.
For JJ power tubes, I've actually never had a set not fail on me, LOL. Don't like how they sound either, personally. I've not tried a huge variety, TBH, but I've had EL84's, 6L6's, 6V6S's and E34L's. Actually, I take that back. The 6V6S's do sound nice, but mine blew.
I hate to be negative, but even Chinese power tubes have been more reliable in my case. And nicer-sounding. But to be fair, I love Chinese tubes, LOL. Too bad they're not making them anymore.
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Gtrjunior
New member
I like the Chinese tubes too!
There’s a newer brand called PSvane or something. I haven’t tried them at this point but I have read good things about them online. And iirc, they are Chinese….don’t quote me on that though. And TAD are Chinese as well. Are they no longer being made?
I haven’t bought tubes in several years now.
Rex_Rocker
Well-known member
Yeah, I've heard about Psvane too. I heard they were making tubes too now. Don't know how they are. I do know they make several of the TAD STR tubes.
But I meant Shuguang. I haven't tried the old square getter 12AX7's, but those are well regarded because that's what came in 90's Mesas, Peaveys, Soldanos, and Marshalls. But the so-called 9th Gen 12AX7's are also well-regarded as being good-sounding for high-gainers. I quite like them, personally. Solid bottom end, not overly scooped mids like EHX/TS (IMO), a nice grindy high-mid emphasis, and not overly bright highs (again, like EHX/TS). Reliable too. The problem I always had with them is for V1, it's kinda hard to find one that isn't slightly more microphonic than what you need for a blisteringly high-gain amp. But they were so cheap, you could buy a few to cherry pick the nicer ones. The nicer ones definitely had some magic to them.
Their power tubes kinda follow the same recipe of big solid bottom-end and angry-sounding mids. But they had a huge variety making them for several resellers like Ruby, ARS, Groove Tubes, TAD, etc.
But now they're gone. They've been out for a few years now because the factory burned down. Supposedly, they've been trying to get it up again, but it's been a few years, so who knows.
I think Psvane has something to do with Shuguang. As far as I understand, Shuguang is government owned, and Psvane isn't?
Gtrjunior
New member
From what I understand the people that started Psvane are former Shuguang employees.
Was looking in tune depot’s website earlier today and they still have Shuguang tubes in the menu. I didn’t click on them to see if they actually had stock of them though.
But I agree with your assessment of them. I always liked the tone and reliability of pretty much all of the Chinese tubes I have tried over the years.
beaubrummels
Well-known member
Clarification: I get a spike to the speakers with the amp "not in standby" and just turning the power on. I don't know the right way to say it. I thought 'open' meant not engaged, e.g. not in standby mode. Or maybe a standby 'closed' is 'not in standby'. However you say it. But in particular, my AC30 without a standby at all puts out the loudest spike just by flipping the power switch.
When I say on, I mean in the Play and make noise position. As to how, or why your particular amp does is beyond me? It shouldn't, but if it does, there may be something to look at. There are so many variations of AC30 that it is truly a matter of detective. Psionic Audio has a lot of know-how on AC30's specifically, he is a good source for learning about their shortcomings and strong points over the years. There are some models that he is not fond of, to say the least. Check him our if you want to glean some knowledge about your amp more specifically.
