I used to wonder how they measured current when set 📐 up in x-y mode

So I just accepted it 

So now I think they are just showing voltage. (Ya think ?!?!?  )

And yeah isn't that what oscilloscopes do 

I don't know the complete details I think the volts per division is set to "make it right" I'll see how it's done when I actually do this.  (Eek  )

So what's all the fuss about well in my book 📖 I'm working through the have a sections where students use a Tektronix 575.  I would love to have one but I looked at some and they are big and heavy, have lots of tubes (huh?!?) and $$$$ 

Dont get me wrong I would love to have one 

Now credit to the book 📚 they have instructions how to monitor Ic on the scope which is cool.

Seems like I saw on MEF one of the members here posted some beautiful pics of output characteristic curves 

So I got to wondering on a TO-220 is the metal tab the same for every transistor in that package?

This gets further convoluted because seems like I remember some voltage regulators in that package 📦 and the metal tab possibly being ground.  Like when you guys fixed my audition chorus 

Then seems like I remember on TO-3 packages like the metal output transistors (I'm not cheating and looking while typing this so hope I am right but the metal case is the collector?)

Hence why people have to use mica insulators and stuff.

So back to the TO-220 I'm off to see if the metal tab
-is always the same thing
-or no 

And oh yeah obviously the metal tab with a hole in it is for attaching to a heat sink but don't necessarily assume a heat sink is ground 

At the end of the day I guess the best thing to do is just make sure what stuff is before connecting or soldering or placing in service.

Since this post is already a rambling stream of consciousness I'll add that I guess the white paste is not an electric insulator it is there to conduct heat and aid in heat transfer 

Which brings me to dielectric grease how many years did I put this on spark plugs and stuff not knowing why it's just what I am supposed to do.

Seems like I should know if it conducts or insulates electricity.   

Plan to do this tonight or this weekend possibly this afternoon if I can.

Btw I don't come up with this on my own all credit 💳 goes to the author of the book I'm working out of. 

It took me a long time to get to this point where I'm looking at a circuit and actually making the circuit that HAS A TRANSISTOR      so I'm stoked to say the least.  This will be my first ever  hopefully one of many.

That said let's get on with it.   

A diagram of the circuit I need to make is shown below

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My instructions are to vary VBB until VCE is 6V
by adjusting a variable resistor 

Then measure and or calculate VB, VRC, VRB, IC, IB, Beta, VCB, and VBE

Then after that I do the same with VCE at different values.  Investigating linear, saturation, cut-off etc 

And a lot different cool stuff.

Here's my victims

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A zener diode can act like a normal diode when it is forward biased

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Seems kinda obvious now that I think about it.

  

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About the author 

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Contents

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Its rad 

I got pretty excited looking at H. Then I looked at the others and got even more excited.

Its like the ten commandments of transistors

  

Sorry just thinking out loud 

For the longest time I was thinking that making contact with components of an energized circuit with the leads of a (handheld) multimeter was gonna be a short
 
Well...now I know that IT IS NOT
And the (I presume) explanation for that is there is no current introduced between the leads only potential
(I'm sure there are limitations to this concept)

So I'm wondering how people can slip up and short something out  while probing with their multimeter leads and it occurred to me that what happens is they contact two parts of the circuit WITH THE SAME LEAD

 

And....that IS a short.   

I did an experiment to try to prove a point to myself or a forum member or a complete stranger 

The point I wanted to make was an open circuit can be constructed and as long as it's open the voltage will remain the same.

Unfortunately I have failed in that endeavor but fortunately succeeded in learning or affirming stuff I have read about.

I plugged in a constant dc power supply 13.8 v and tested voltage 

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Next I grabbed a resistor added it to the open circuit and got some good results 

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So life is good yeah I'm intrigued and fascinated and life is good

But then I got greedy by grabbing a large value resistor and that's when everything fell apart   
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And no I don't understand it but I'm thinking it has something to do with my meter's (internal resistance?)

So yeah I'm off to try and learn about that 

Ok I know this is mere childs play for most here but I thought it was cool 😎

Guess the voltages for A,B, and C in each

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I got to thinking I guess these guys flash sixty times a second.     I thought about making a video with my phone then playing back slow and seeing if I could catch the on and off.

I tried to get it to flash 📸 with my signal generator but couldn't get any light 🚨 out of it.

Maybe the forward voltage ⚡ Vf is way higher than 20 Vp-p

 

I'm so glad
I'm so glad
I'm glad I'm glad I'm glad 

I finally finished a book
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It took me about a year but to be fair progress slowed during the summer (I cut grass on the side and it gets pretty crazy)
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So you're thinking yeah that's real dope and all but it's not like you're fixing any amps 

Ok I'm getting to that so the good part is this book is next 
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And check it out
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So I'm stoked I actually started the second book at one time and made it to the zener chapter then realized I better do the other book first 

The first book was really cool but got kinda crazy at the end the last chapter I was measuring rise time and tilt 

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I'm hoping in about six months or so when somebody reports the E B C voltages I may have somewhat of a clue 🧩   

Seems like it's always darkest before the dawn  I'm so ready to be done with this book I literally have like 25 pages to go and still slugging it out 

Anyhow the assignment was to put together the circuit
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Then calculate the resonant frequency and adjust signal frequency until the voltage across the resistor is maximized.

So I did everything
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and on the scope display the top is Vr and the bottom is Vin
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So I had calculated 50.33 khz and ended up with this
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So I really like how in this field the experiments closely match the calculations 

So now I somewhat can start to comprehend how an old radio tuning capacitor can pull in a radio station but what bothers me is that is only one variable.  Or rather someone tuning in a station isn't adjusting a capacitor AND inductor.
Anyway don't want to open a can of worms 

Finally got around to trying this thing

I splurged a few bucks on a manual

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I hooked it to a box fan 

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So it has life but I couldn't get any response from the single phase mode aside from a small reverse movement I did reverse polarity to try it to no avail

I don't see any fuses anywhere on the unit or in the manual nor a power cord 

I need to calculate approximate watts of a dollar store box fan 

I searched I promise  there is so much ➗ divisive content on the interwebz a guy could spend the rest of his life reading about it.

So the standby switch on my toob amp savage rohr 15 is a good thing  or...no it's killing toobs   

I'm not 🚭 stressin out about it I'm 61 (eek  ) so the amp and toobs will probably outlive me 
And I'm a strictly at home bedroom wanker no three sets a night at the pub 

The only time I use or was using it was start up and shut down and in between changing pedals etc

Like I said it's not a big deal I'm just gonna do what you guys tell me to or not to do.   

Also it is toob rectified if it matters
Also if it matters I always have the preamp maxed out and the power section set at 0.000001   

Made another go at this since I worked a few chapters in my text book

Wiring this old artifact ballast in series with a 1000 ohm resistor and putting variable frequency through it.  With predictable results 

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So now when people see me wandering around wondering what I'm thinking about it's gonna be....."so the resistance of the inductor (ballast) goes up.....

Interesting last night I did an experiment out of my textbook they had me put 125 hz in a transformer primary (channel one scope probe attached) and then channel two scope probe on secondary with a 100ohm resistor.

They had me ground one side of the resistor and then the other side.  One side was in phase and the other was out of phase.

I was like hey cool but then I realized some speakers (or amps rather) dont have output transformers   

What's really 🪲🐛 bugging me now is not remembering if it was in or out with no ground 

Noticed this in a trash 🗑�🚮 picked Crate
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After a little research maybe it's possibly a TDA2030 or LM1875 ?

 

I am seeing old Dukane 🎤🎙� mic preamps and they have stuff like "24v DC input"

Wondering if there is/was a specific reason for this 

Maybe the answer is because it works? Idk 

Btw HAPPY HOLIDAYS 🎄 🎁

Man talk about a nightmare


Btw this is not something I'm working on trying to repair.  Just a junk PCB 
They had some cool heatsinks on them too.

I'm blaming it on lead free solder but I don't know if it is or not.  I tried some tricks I have read about like adding flux and leaded solder.

On both there was one leg 🦵 🍗 that would not melt 

Ultimately they did give up.

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If you listen to fools...
The newbz rules....

Anyhow...been looking at power supplies

I'm trying to decipher terminals that show up in the pictures 🖼� of many of them

I have attempted to identify and lable appropriately....

What the heck is S- and S+ ?

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Thank you in advance 

Also I'm seeing older power supplies that are called switch mode I'm kinda familiar with those rectangular plastic ones that look like what hooks to laptops and stuff but I guess early older switch mode externally kinda looked like linear power supplies I see some called Op-Amp power supplies.

Also I see some schematics for a (7815 and 7915 ?) power supply looks like I could assemble if you like that. 

 

I have a harness from a boat anchor power supply I don't want to cut it up so I desoldered the male connectors from a circuit board 🛹
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Here they are with the harness (the big 🔌 plug top right connects to the PS)
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I just need to attach some wire/leads whatever to the male doodads
I think the pins remove and I attach wire or just get pins with wire and install

Thanks