Critical thinking

[Steve Conner]

Well, that comment may seem stupid, but it's actually not as bad as I'd expect for TGP.

For a start, you can make a mechanical analog of an electrical circuit, where inductance corresponds to mass or inertia. (Capacitors become springs, and resistors are friction.) The math all works the same.

Then, say you try to design a bigger and bigger OT, with a higher ratio to work with big transmitting tubes. The large size of the transformer, and the thick insulation needed for high B+, mean that the leakage inductance gets bigger than you'd want.

The result of the unwanted inductance is that the OT does indeed get "sluggish". In more technical terms, high frequency response starts to fall off, and you can't make the top octave of the audio band any more.

But is this an issue for guitar amp OTs? I doubt it.

Loudspeaker designers use a different analog, where capacitance is mass, and inductance is spring compliance. This is also valid, and more convenient because the speaker motor actually does this same transformation.

For what it's worth, analog electronics got its name from the practice of using electrical circuits as analogs for hard-to-solve problems in mechanical engineering.

[Enzo]

Chuck, My house is cold.

When I visit my sister, she turns the thermostat all the way down to 69 at night, she thinks that is cold. Remember when they used to tell us all to turn the thing down to 55 at night and just grab an extra blanket? Well we did that, still do, except we now set it to 50. And after a while, we quit turning it up when we were awake. SO yes, my house sits there at 59 degrees all the time, until it warms up outdoors. Warm day in sspring when it gets up to 55 outside? Open the windows. Yes, the bowl of hamburger helper cools off fairly quickly, but the beer stays cool a lot longer.

[Chuck H]

Well kudos to you for minimizing your carbon footprint. Also, my thermostat reads incorrect. Probably about three or four degrees high. I set my thermostat for 68* during the day (so 65* in reality) and 60* at night. I guess I just can't be cold ALL THE TIME. When it's 30* outside I need warm inside. Otherwise I'd climb a clock tower. I'm reminded of a Lewis Black piece where he say's "It was so cold this winter I couldn't even have a thought. The sentrnce in my head would go: Maybe I should go down to the... F@#K IT'S COLD."

[wayward bluesman]

It's been a week or two since the last post, but it's a fascinating subject and I just thought I'd weigh in from the perspective of a member of the generation most of you are bemoaning. And the truth is, I think you're mostly right.

I'm in my mid-20s and have been doing electronic repair for about a year and a half. Before I started, I had a very weak grasp of electrical theory despite a degree in aerospace engineering AND another year and a half in commercial electrical system design (mostly CAD work). Electronics wasn't offered at my high school, though we were lucky to get a semester of introductory physics. For most engineering disciplines in college apart from EEs and CEs, electricity was coupled with magnetism, optics, etc. for a single semester taught out of the physics department. Even then I had little interest in learning circuits nor did I find it very intuitive; unfortunately, it didn't matter very much. We had an awful professor who had a nasty habit of creating multiple choice tests with no right answers and would typically curve the scores at least two grade levels because most of the students had done so poorly. Through the limited experience I've had with other people near my age and of similar educational background, this isn't all that uncommon. In the end, however, I graduated with a degree coupled with a general disenchantment with engineering as a whole.

Unfortunately, it wasn't until much later that I finally noticed the connect between a lot of the control theory/signal analysis I had been taught in aero and audio electronics. Music had long been a major force in my life and I'd finally found an excuse to involve my technical side. It wasn't until I started trying to diagnose and repair audio electronics, however, that I finally got the real education. When I first started I was interested only in tube amps but, as luck would have it, I learned (and am learning) to do the solid state stuff as well because that's where the need is. And, truthfully, it's developed into a real a passion, so much so that the end goal for me lies somewhere in the design world. But it certainly hasn't been easy. Obviously, learning and understanding the theory, the components, the circuit topologies takes a LOT of time and effort, but when it's something you genuinely enjoy - all the better. To bring it back to the sentiment originally expressed in this thread, I think the harder aspect for me IS the critical thinking, the logic, the diagnostics. It's definitely a mindset that, while an absolute necessity for this kind of work, doesn't always come naturally. And, yes, I absolutely think there's a growing disconnect between what most people assume is learned from a formal, technical education and the skills actually needed to solve real-world problems. The fact that I know what a Laplace Transform is doesn't help me find a shorted diode any faster. That's not to say that there wasn't an honest attempt to teach a lot of these skills in the classroom and even the labs while I was in school, but I wouldn't have put a lot of stock in it. I'm sure I learned more from involvement with some of the design teams where we actually built and operated most of what designed on paper, but we were in the minority. Very few of the senior design projects, for any of the engineering disciplines, were hands-on.

One last note - has anyone here read "Shop Class as Soulcraft" by Matthew Crawford? On the one hand, it's part of what inspired my foray into electronic repair and, on the other, is an excellent view on many of the undercurrents in this thread, from the gradual disappearance of practical, technical subjects taught in school to the devaluation of "blue collar" work to the disconnect between people and the machines the use everyday to the growing lack of culpability, critical thinking, of views on utility once valued in our society. If not, it's definitely worth checking out..

[Enzo]

Hey, thanks for the thoughtful post. And it never hurts to say "You old people may be right" to start out.


One reason I dwell on troubleshooting is one of the Enzo-isms in my shop philosophy:

Troubleshooting skills will get you through a lack of knowledge a lot better than knowledge will get you past a lack of troubleshooting skills.

And I think that is at least part of your point.

And I think you will find, if you look at it, that troubleshooting doesn;t care if you have tubes or transistors, or relays, or plumbing, or or or... The approach is the same, only the details are different. A shorted rectifier is a shorted rectifier, whether it be a 1N4007 or a 5U4, you find it the same way. And a leaky or shorted filter cap really doesn;t care what kind of rectifier is charging it.

Laplace? I hear you. I could probably sit down and explain the idea behind Thevenin, but in over 50 years of soldering, I can;t say I ever had to sit down and "use" it. And I forget what it was that DeMorgan was chatting about - I think ti was some sort of equivalency between logical combinations, but I could be thinking of something else. In any case, when troubleshooting, I need to be able to read the logic and understand how the gates work, I don;t really need to know that these things and-ed together are equivalent to something else or-ed, or whatever. WHichever form the relationship occurs, all I need do is read it.

Everything is a process, and one needs to look at it like that. As I like to say, it ain;t the parts, it's the circuit. Without that understanding, we get questions like "what resistor do I change to (do whatever)?"

You want to learn this stuff? I swear there is no better way to get a handle on this than to have to explain it to someone else. Teaching is the best form of learning.

[Jazz P Bass]

"You want to learn this stuff? I swear there is no better way to get a handle on this than to have to explain it to someone else. Teaching is the best form of learning. "
Awesome statement, Enzo.
PS: I looked up 'Enzo-ism' in the dictionary.
Huh, it is not in yet.

[J M Fahey]

PS: I looked up 'Enzo-ism' in the dictionary.
Huh, it is not in yet.

Ah !! , but it should !!
Their mistake.

[Mark Hammer]

You want to learn this stuff? I swear there is no better way to get a handle on this than to have to explain it to someone else. Teaching is the best form of learning.

Could not agree more. I must have taken some 7 or 8 stats classes between undergrad and graduate school. Never understood the damn stuff until I was obliged to teach a 4th year honours stats seminar.

So why does it work that way? Simple, teaching obliges one to prioritize and organize knowledge. It forces you to get the concept, not just collate the tidbits that emerge from the concept. And it also forces you to learn enough to be a step ahead of the students....which is a lot different than simply knowing enough to pass the exam. Finally, there are a lot of things in life that you don't really understand until it comes out of your own mouth (the trick is to make it look as if you already understood, should they come out while in public).

"Teaching" takes many forms. I used to tell my students that they may think they consulted the "whiz" in high school for help, but what they didn't realize was that the person was a "whiz" because they helped. I probably have well over 40,000 posts between my time here, on Ampage, on the DIYstompbox forum and on several others. Some of it IS just "farting around with the guys", but much of it is an attempt to make something clearer for someone else. And while doing that, I often end up making things clearer for me.

[wayward bluesman]

To that end, I'm very grateful for the all the knowledge and support I've gained from all of you in this forum. It's often my go-to resource when something on the bench has me stuck; it's comforting to know that if I'm having a problem, chances are someone on here has already posted about it and gotten a dozen replies from most of you guys. I've got probably a hundred threads bookmarked and several others printed out and paper-clipped inside my tech notebook.

In the spirit of advice giving, anyone got any for getting heat transfer paste out of clothes? : )

[Enzo]

Uh, no, but I have discoverd several ways to take a small spot of it and make it grow into a large spot by trying to clean it.

I maintain that if you don't get the heat grease all over yourself, you must be doing things wrong.



I hate to admit how many times I sat down here, prepared to explain how something worked, and as I started composing my post, discovered that what I had in my head up till then had been wrong. Working on my explanation caused an epiphany. I'd realize I had thought something out backwards or made an unwarranted lead somewhere. Thankful that I'd seen the light and corrected myself before blathering online, I also had to wonder how many times I did NOT catch myself and spewed nonsense out across the interweb.


And there is that whole filling in the blanks thing. ON many things, I have a conceptuaql understanding, enough to see the flow of the circuit and work with it. But when trying to make it clear for someone else, I often bring some small detail into focus for myself. WHich is what Mark said.

[wayward bluesman]

Enzo, I've always wondered - how on earth do you have the time to actively repair AND run your shop while maintaining your presence on this forum? You're often one of the first responders on the vast majority of the troubleshooting threads and they're usually not just one or two line posts either. It almost goes without saying how much appreciation everyone on here, myself included, has for the thought and detail you put into your posts, including the time it must take to reference the thousands of schematics these guys mention; I just can't figure out how in the hell you have the time.

[tedmich]

Enzo, I've always wondered - how on earth do you have the time to actively repair AND run your shop while maintaining your presence on this forum? You're often one of the first responders on the vast majority of the troubleshooting threads and they're usually not just one or two line posts either. It almost goes without saying how much appreciation everyone on here, myself included, has for the thought and detail you put into your posts, including the time it must take to reference the thousands of schematics these guys mention; I just can't figure out how in the hell you have the time.

Enzo doesn't sleep and only pauses momentarily to swap out his glucose/vitamin IV....kidding, he's a diligent guy with a capital D!

[Jazz P Bass]

Actually, Enzo has gone through Calvin & Hobb's (remember them. I loved that cartoon!) 'Transmogrifier'.
He has been cloned.

[g1]

And all this time I thought his secret was elves, like that other guy that looks like him.

[Enzo]

I am an entire staff of people in some third world country, using special google-amp software.



I have the internet on my bench, and whenever I want to think about something else I look over here, and speak my mind. If you read enough of my posts, you'll see some common themes. So a lot of these posts more or less write themselves, at least from my point of view.