Ampeg B15-N Capacitor ID

[beans-on-toast]

This is what happens when a component is used that does not meet the needs of the circuit. These days, this is addressed in products that are safety certified because resistors contain a rated voltage breakdown specification which depending on the application can make the component a CCL component.

Things are way better today than in the past. So is component manufacturing conformity and certification. One reason why I recommend to buy new over vintage.

 

[agedhorse]

I deal with this all the time, resistors are sometimes a CCL component (safety regulated) in tube amps and power supplies. They are used to limit the voltage and current (according to ohm's law) to a safe value in the event of a fault (say plate to grid at the input tube). These resistors are pretty thoroughly specified with regard to breakdown as well as being an approved component.

When you look at modern (as in the last 20 years) schematics, you will see components with a triangle or a symbol designating that they must be replaced with the identical part. That's because they are involved in the safety certification of the amp.

 

[beans-on-toast]

Fault tolerance is an important part of design. Even in software systems.

 

[Old Garage-Bander]

It

Don't get me wrong. I appreciate all the sage wisdom of people that do this for a living. I just don't think that a lot of this stuff is rocket science that needs an EE education or trade school or apprenticeships to figure out. Most of the amps and radios I work on are based on circuits and components that were designed 50 or more years ago. There is so much published on this that there is no magic involved. Now if I were to try to build, design or repair the guts of an iPhone, I would be out of my league.

It's also been about fifty years since we last set foot on the moon. Yet we're currently having trouble doing that again. So just because someone did something a long time ago, doesn't automatically make it easy-peasy now just because there is now a lot of information, both good and bad, readily available at our fingertips.

No, it's not rocket science, if it were all the techs and EE's would be working at NASA or SpaceX. But it is still a subject that requires disciplined study equal to the task at hand. If all you want to do is experiment in a willy nilly fashion because you saw what some Youtuber did, and you are not concerned with the outcome, then fine. But don't be dismissive of those who put in the work to achieve levels of education and experience for higher goals.

In spite of the suggestion to not get you wrong. (Why do people only say that when they are reasonably sure that someone will get them wrong?) I don't see any other way to take it when ruling out having an EE, attending a trade school or apprenticeship, is relegating this to something just anyone without any background can do. For someone to use all of that information on the Internet requires gaining at least the basics of the subject matter at hand. Half the battle is in knowing which of it is legit and what isn't.

The dismissiveness shown here makes it hard for me to believe that any appreciation for the wisdom of others is at play. But giving the benefit of the doubt, perhaps it just comes from not understanding what's involved in anyone's education or background in electronics.

The less someone knows about a subject, the more likely it is that they think they know everything about it.
I was that way when I began my education at an electronics trade school. At first I thought I knew everything about everything. But the more I learned, and the more experience I gained over the last fifty years (there's that fifty thing again) the more I realized what I didn't know. I've finally reached a point where I'm convinced I know nothing about anything.

 

[Passinwind]

I've finally reached a point where I'm convinced I know nothing about anything.

My man...

 

[agedhorse]

It


It's also been about fifty years since we last set foot on the moon. Yet we're currently having trouble doing that again. So just because someone did something a long time ago, doesn't automatically make it easy-peasy now just because there is now a lot of information, both good and bad, readily available at our fingertips.

No, it's not rocket science, if it were all the techs and EE's would be working at NASA or SpaceX. But it is still a subject that requires disciplined study equal to the task at hand. If all you want to do is experiment in a willy nilly fashion because you saw what some Youtuber did, and you are not concerned with the outcome, then fine. But don't be dismissive of those who put in the work to achieve levels of education and experience for higher goals.

In spite of the suggestion to not get you wrong. (Why do people only say that when they are reasonably sure that someone will get them wrong?) I don't see any other way to take it when ruling out having an EE, attending a trade school or apprenticeship, is relegating this to something just anyone without any background can do. For someone to use all of that information on the Internet requires gaining at least the basics of the subject matter at hand. Half the battle is in knowing which of it is legit and what isn't.

The dismissiveness shown here makes it hard for me to believe that any appreciation for the wisdom of others is at play. But giving the benefit of the doubt, perhaps it just comes from not understanding what's involved anyone's education or background in electronics.

The less someone knows about a subject, the more likely it is that they think they know everything about it.
I was that way when I began my education at an electronics trade school. At first I thought I knew everything about everything. But the more I learned, and the more experience I gained over the last fifty years (there's that fifty thing again) the more I realized what I didn't know. I've finally reached a point where I'm convinced I know nothing about anything.

Indeed, and when somebody who has the necessary education, skills, and experience sees what they see from DIY attempts that often end poorly, it's a disservice to let folks think that just because they saw it on the internet, it's a good idea and they are well enough equipped to blindly go forth.

 

[beans-on-toast]

The more you know, the more you realize what you don’t know.

 

[Old Garage-Bander]

Here is my take on DIY. Nothing wrong with it. I actually find it funny when people claim that only a qualified technician should work on something. That is utter BS. I started working on amps when I had some problems with my Ampeg V4B. I am NOT a trained electrician, but I am a scientist and work around a lot of very dangerous equipment and chemicals that can kill very effectively. I have always been a DIY'er, even with million dollar equipment.

That being said, I am trained how to research and solve problems. That type of training makes it easy for me to approach a problem and figure it out, whether that is rebuilding an car engine or fixing an amp. This means doing lots of research, asking questions and not willy-nilly futzing with anything. It also means getting the right tools for the job. It also means fully understanding hazards and anticipating problems.

In the OP's case, it is concerning that a burnt resistor was confused with a capacitor. Not that it is a fatal flaw, but if such a person wants to do DIY they have a lot of learning to do. The last thing they should do it repair the AC cord and plug it in and see what happens.

If a person is not prepared to learn and do it right, they should not attempt a project. However, if they are like me and curious and prepared to learn (and be prepared to probably spend more money that it would cost to get it serviced in a shop), I think pre-IC and SMT stuff is a perfectly good hobby and safe if you take precautions and pay attention.

I am currently building a new 5E3 clone. Lots of fun.

Your methods are what I like to think of as cross-disciplinary. You've learned how to approach a problem in one area, and those same skills are useful in approaching other, even very different subjects. This is an instance of someone who has learned how to learn. The other important aspect that you bring to this is critical thinking. Where many people without your skills say "why not", you ask "why."

 

[Basslice]

I simply said a person does not need advanced training to successfully engage in tube amp repair. This is factually correct. I did not imply that people that have advanced training are anything less than they are. They are qualified experts. If you took umbrage to my saying that a person does not need that level of advanced training as a slight to your profession, then I apologize. That was not my intention.

No, it's not rocket science, if it were all the techs and EE's would be working at NASA or SpaceX. But it is still a subject that requires disciplined study equal to the task at hand. If all you want to do is experiment in a willy nilly fashion because you saw what some Youtuber did, and you are not concerned with the outcome, then fine. But don't be dismissive of those who put in the work to achieve levels of education and experience for higher goals.

There is so much information out there. Youtube is one source, but as you note, one has to be very careful when taking advice (medical or otherwise) off the internet. There are books, and technical service manuals and schematics that are very useful. My local library is full of them (although I think that the concept of a library is lost on even my PhD students). They try to do research based on Google searches and I have to constantly remind them that no algorithm is a substitute for a real search.

In spite of the suggestion to not get you wrong. (Why do people only say that when they are reasonably sure that someone will get them wrong?) I don't see any other way to take it when ruling out having an EE, attending a trade school or apprenticeship, is relegating this to something just anyone without any background can do. For someone to use all of that information on the Internet requires gaining at least the basics of the subject matter at hand. Half the battle is in knowing which of it is legit and what isn't.

I agree 100%. I never ruled out the value of advanced training. I just said it is not a prequisite for tube amp repair or building - and I stand by that. There are right and wrong ways of doing everything and an uniformed person stumbling into anything can get it wrong - equally, an informed person can (and do) get it right.

The dismissiveness shown here makes it hard for me to believe that any appreciation for the wisdom of others is at play. But giving the benefit of the doubt, perhaps it just comes from not understanding what's involved in anyone's education or background in electronics.

You have taken my comments as dismissive, which is maybe a misrepresentation of what I have said - unless you are of the mind that only a certified or degreed person has any business messing with an amp. That to me is hubris and I do not have a lot of patience for that train of thought. Again, I have nothing but respect for people that are trained and experts. They are truly artisans. I am one in my own field. I spend time at radio swap events and things like that (with my son) and am amazed and awed by the amount of knowledge that is out there. I am also saddened that like the Elves going over the seas, much of these experts are dying off and a lot of this stuff is in danger of becoming a lost art. I bought a highly rated academic book on electronics a couple of years ago but returned it because it only discussed vacuum tube / valve technology in a few pages.

I will also note that I would never charge anyone to work on or service their equipment nor represent that I am qualified to do so. I am not licensed nor do I pretend to be an expert. That would be criminal.

The less someone knows about a subject, the more likely it is that they think they know everything about it. I was that way when I began my education at an electronics trade school. At first I thought I knew everything about everything. But the more I learned, and the more experience I gained over the last fifty years (there's that fifty thing again) the more I realized what I didn't know. I've finally reached a point where I'm convinced I know nothing about anything.

I agree here as well. I love to learn and to experience things. That is why I love music. Playing music, learning how to play, learning how to write, learning how to record... I also love learning about electronics and all that goes with that. I love building motors.

I also appreciate how people on this forum (and some others) are willing to share their knowledge. It is a really great community. I don't cherish hurting people's feelng, but I also do not think anyone has a monopoly on learning and doing. I speak (or write) my mind. I also tend to avoid using too many phrases like "IMHO" - if I write something, it is of course my opinion. I don't always get it right either (as my wife is happy to remind me). That is just the way I roll. I hope that the information I have shared for years on this forum has been helpful to people. But like you note - caveat emptor....

 

[agedhorse]

There is a difference between having advanced training and having training... most of those wishing to do work themselves on their amps have NO training, and this is not a good idea. I often see the results of such repair attempts and usually it's the cause of MORE damage, unrelated to the original problem.

Part of training is learning what NOT to do, just like diagnostics often identifies what is NOT the problem.

 

[Basslice]

There is a difference between having advanced training and having training... most of those wishing to do work themselves on their amps have NO training, and this is not a good idea. I often see the results of such repair attempts and usually it's the cause of MORE damage, unrelated to the original problem.

Part of training is learning what NOT to do, just like diagnostics often identifies what is NOT the problem.

Having spent most of my life either being trained or training others, I often forget the number of people that do not know how to approach a problem. The methodology is so deeply ingrained in me. My dad was also a PhD scientist. When presented with a task you first research the crap out of it. Then you identify (and if possible) write down all of the hazards. If you don't do those two things you are in for wasted time, disappointment, increased costs, and possibly bodily harm. Most people do not do that without training (or training on training). It is automatic for me.

Thanks for reminding me and others.

 

[S-Bigbottom]

I know a few, got relatives also that are always "fixin'" stuff.

Everything they own is a pile of junk when they get done with it. "Well... I was gonna fix ___ but this happened." Is said often when asked what happened to the nice ___ they had.

One of them can somehow manage to break a single ball bearing, yet they are out their grinding away at stuff like they know what they are doing.

 

[agedhorse]

I know a few, got relatives also that are always "fixin'" stuff.

Everything they own is a pile of junk when they get done with it. "Well... I was gonna fix ___ but this happened." Is said often when asked what happened to the nice ___ they had.

One of them can somehow manage to break a single ball bearing, yet they are out their grinding away at stuff like they know what they are doing.

Yup, and it’s never their fault .

 

[Old Garage-Bander]

To no one in particular:

I've said this on the TB forum before. We must keep in mind that many people who come here have no clue as to what they are getting into when diving in to an amplifier.

That's no fault of that person. It's not a judgement of their character, any more than if I were to say, my car won't start, what kind of new tires do I need to install to fix the problem. Those with a background in auto-mechanics would warn me that I don't know what I'm doing. They would suggest I get my car to a qualified mechanic.

When we participate here, we must remember who else is reading what we say. If that person jumping into a amp repair has a Phd and the critical thinking skills that come with such disciplines. Or one has an EE degree, went to an electronics trade school, or they read one of the many books about basic electronics and repair, it does not matter. Those people have at the very least, some idea of what they might be in for. At the very minimum, they know that there are right and wrong ways to approach the task. It is those other folks to whom we do a disservice when we don't warn of the possible dangers, or we suggest they take their amp to a qualified technician.

If someone were to include their relevant skillset along with their desire to do whatever they plan. It would go a long way towards getting to the real problem without having to drag out of them what they know or don't know. Likewise, for those instances when we see someone making a statement that obviously disqualifies them from any notion of having the required skills. Recall that this thread started that way.

The OP misidentified the single component that everyone learns about first, in DC circuits 101. Yes, the very device, who's basic unit of measurement shares the same name as the laws that govern how that device will operate in a circuit.

We all may have differing opinions about what qualifications are necessary to work on an amp. There is no point in continuing that discussion. As someone who's been knocked on my butt, by a high voltage power supply in tech school, and lucky to have not had more than just my pride injured on that day, I can't abide by the thought of someone else being hurt due to lack of sufficient knowledge and experience.

I, and others here will continue to warn of the dangers and suggest against DIY repairs, until we have a better feel for a person's qualification. That effort will be intensified when we sense an elevated misunderstanding of the most basic aspects of electronics, as was demonstrated in the original posting.

 

[MVE]

I agree with Basslice on this.
Its perfectly ok to troubleshoot your own gear and you don’t need to be a trained tech to do so.
I also recognize Agedhorse’s caution that mistakes can often cause more damage that will likely cost more money to fix than the original problem.
But everything I know in this world I learned by making mistakes and I love learning.

 

[agedhorse]

I agree with Basslice on this.
Its perfectly ok to troubleshoot your own gear and you don’t need to be a trained tech to do so.
I also recognize Agedhorse’s caution that mistakes can often cause more damage that will likely cost more money to fix than the original problem.
But everything I know in this world I learned by making mistakes and I love learning.

Also note that mistakes can hurt or even kill a person who is unaware of the safety precautions involved with servicing electronics.

When I was training techs for a chain of hi-fi stores back in the early 1980's, there was this cocky guy who was pretty smart but not well trained. His problem is that he dismissed pretty much everything we tried to teach as unnecessary, he could (sort of) fix anything. A couple of years later, I ran into somebody who had worked with him, he said he was working on a tube amp, got badly shocked, went over backwards off of his stool and landed on some amp chassis stacked behind his bench. Yeah, I'm sure that hurt, but the worst part for him was him looking up to see the amp he was working on falling on top of him. He got badly hurt, don't know how the story ended though.

When I teach electrical contractor safety, there are 2 major risks associated with electricity. The first is electrocution (especially with 480V), the second is working on a ladder and getting shocked, and falling.

Yes, the risks are real.

 

[beans-on-toast]

I must have liked getting zapped as a kid when soldering inside point-to-point wired tube radios. That got me started. I eventually graduated to TV sets. I had a transistor trainer set that took you through 1, 2, 3, and 4 transistor circuits. A great learning experience.

My neighbourhood had a couple of repair shops that sold parts. The radiomen helped me out, as did a ham radio operator whose day job was repairing avionics. Informal training back then was people giving back which I never forgot or failed to appreciate. It’s nice to be able to do that now.

I honestly don’t know anyone who went on to formally study electronics that didn’t get their start building or repairing some sort of circuits, often with some help. It’s where your interest in the subject starts.

Having said that, amps are dangerous.

 

[Brennan]

Here is my take on DIY. Nothing wrong with it. I actually find it funny when people claim that only a qualified technician should work on something. That is utter BS. I started working on amps when I had some problems with my Ampeg V4B. I am NOT a trained electrician, but I am a scientist and work around a lot of very dangerous equipment and chemicals that can kill very effectively. I have always been a DIY'er, even with million dollar equipment.

That being said, I am trained how to research and solve problems. That type of training makes it easy for me to approach a problem and figure it out, whether that is rebuilding an car engine or fixing an amp. This means doing lots of research, asking questions and not willy-nilly futzing with anything. It also means getting the right tools for the job. It also means fully understanding hazards and anticipating problems.

In the OP's case, it is concerning that a burnt resistor was confused with a capacitor. Not that it is a fatal flaw, but if such a person wants to do DIY they have a lot of learning to do. The last thing they should do it repair the AC cord and plug it in and see what happens.

If a person is not prepared to learn and do it right, they should not attempt a project. However, if they are like me and curious and prepared to learn (and be prepared to probably spend more money that it would cost to get it serviced in a shop), I think pre-IC and SMT stuff is a perfectly good hobby and safe if you take precautions and pay attention.

I am currently building a new 5E3 clone. Lots of fun.

Thanks, I’ve been working all week so I’m catching up. I wouldn’t dream of winging it w the AC, but like you I work in a technical field and enjoy researching and tinkering. This was my initial shot at research after picking this up for a bargain. The burnt resister has me hesitating. I still think the dangerous AC situation overloaded something. After working in studios for years I have a few folks I can call and I have a few good Bay Area amp guys. Appreciate all the replies. Can’t wait to get er up and running. I’ll post when I figure out next steps. Thanks

 

[Brennan]

It’s Alive! And it’s sounds amazing! TBer David Wallis reached out and offered assistance. We had a few conversations and he advised me how to take precautions. I snipped the “death cap” and removed the high voltage tube to start. Then I cleaned up the burnt board. I had to wait for some parts from flip tops.

 

[Brennan]

Cont. fliptops.net. I ordered a cap kit and new 22k 1w resistors. I ordered a better soldering station to replace my older one. Dave talked me through the process and I used a voltage meter and a surge strip to be safe. My soldering skills aren’t the best but I took my time. The best part of the build was talking with Dave. He was extremely knowledgeable and patient and he had amazing stories. We talked amp repair about ten percent of the time and poopie the other 90. Great guy!
Anyway, the amp is warm and LOUD, although I’m usually pretty reasonable in my office. It sounds great with my vintage fenders but surprisingly amazing with a modern J. Here’s a few pics. I’ll post a vid at some point. Super fun project, amazing value and learned a bunch along the way.
Thanks Dave!