Anyhow so much for my plan getting voltage readings and stuff.  Because the boards face inward and the only way I can get access to the top of a board is by unplugging everything

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Besides why do that when you can do bonehead stuff like remove components for no reason except that somewhere sometime some guy amongst the entire world 🌎 had that part go bad

Oh well I need some practice anyway.

So I removed Q24

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To be fair i did diode and resistance checks but yeah I guess in circuit they could mean anything.

So while all the cool people in town are partying and getting lit and spending hundreds of dollars on fireworks 🎆 🎇 guess what my excitement is:

Testing this PNP device on my peak atlas.

Oh wait I have a multimeter I'll do that first

 

It occurred to me that when checking transistors in circuit power on I can:

Locate the collector and emitter resistors

Measure voltage drops across each

Look at color codes to determine value of resistors

Divide voltage  ➗ by resistance to obtain a value for current

Compare Ic to Ie

Pause to reflect on discoveries

Attempt to draw a conclusion(s)

 

In summary the left side won't get past about thirteen volts
But the other day it started working and working really good. Relays clicking like gangbusters    As in I turned it to almost thirty volts and it held steady. 


Then it went back to messing up again 

Do you think it worthwhile to replace these capacitors

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However seems kind of pointless to ask I know this is not proper form to blindly start replacing stuff.

And to be fair up to this point I was like "dude it's a bad relay"

  

So I was doing an experiment per textbook

Take a 2n3904 ground the base
Put +12 at the collector resistor
Put -12 at the emitter resistor

Ok that in itself was quite a task but I managed and no matter what kept getting a Ve of -3.7v

It took me a while to figure that if base was at ground then thats probably not correct.

So I reconnected configurations ad nauseum and kept getting the same thing 

Meanwhile kept checking that VB = ground.

Finally I was like well hell why don't you check the transistor so I did a diode check with my multimeter and + on base to emitter was showing a one.   

So I grabbed a new one and it showed about 0.67 

Ve with new one in circuit

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Ve with old one in circuit

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And the diagram

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Now the "old" transistor is pretty new from mouser a year or two ago but..to be fair is has been subjected to some abuse like reverse biasing and stuff....

Anyhow I thought I was going crazy 

A new ridiculously heavy toy here

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Btw I'm aware that a lot of caution still needs to be exercised here.  It's now like "oh look an isolation transformer I can do any stupid thing I want and it will be ok" 

I'm guessing that if one were to grab each end of the secondary it would not end well.   

Also there is a third prong that looks to be continuous 

Honestly this will be probably gathering dust for a while.

As a rule ATM pretty much what I do think and have learned is at least have some type of transformer like a step down between me and mains 

If you remember my Voltron Wattmeter I guess it was nothing more than a transformer with a meter.

Btw more caution while looking at various devices on eBay it seems there are autotransformers that aren't round and look like "normal" rectangular transformers.

 

But anyway wow I love how this has some nice cords on each end so I don't have complete chaos with a thousand wires going everywhere 

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It's time for me to learn how these work and be able to test

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Another reason I got them is because I suspect (probably erroneously  ) one side of my 30 volt  dual power supply is only going up to about 13 volts 

I hope these are the same here is one from my power supply

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Wondering now if they are real...idk 

Some really stiff wire going to I presume selenium rectifiers...

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I thought it was bare copper wire and rigidly shaped to avoid contact and shorting out etc..

But (and maybe it's heavy oxidation or tarnish?) but there is no continuity at two outside points on this stuff
 

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However if I touch the probes on the soldered on eyelet terminals I get continuity 

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This IS an old boat 🚢⛵ anchor ⚓ so do you think it's just oxidation?

Ok maybe bust out some sand paper and retry

I'm thinking that using my ugly 120v variac to get like ten volts AC is a pretty bad idea 


So here's my latest plan: 

I have another autotransformer and a few transformers

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So how about mains to transformer (24v) and transformer to autotransformer 

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However my other question(s) is could I not just run the transformer output to a potentiometer to adjust voltage?

(Yeah dirt daubers are bad here)

I was beating my head against the wall 🧱

I was to make this circuit
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So I was trying to set VCE to 12V and couldn't do it.
I started checking stuff finally disconnected the base and could do it

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Reconnect the base and back to zero (no matter how variable R2 is turned.

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It took me a while     

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