You cannot view this attachment.

You cannot view this attachment.

About the author 

You cannot view this attachment.

Contents

You cannot view this attachment.

You cannot view this attachment.

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.   

Quote from: g1 on March 23, 2025, 10:28:05 AMA nice visual reminder that voltages are always in respect (or reference) to something else.  In this case it was ground (common) but it does not necessarily have to be.

For bonus points:
1) what are voltages at A and C with respect to B.
2) what are voltages at B and C with respect to A.
 

Ok I see G1 actually got me because on number two node A is at ground 

Anyhow here are my answers

You cannot view this attachment.

Anyhow thanks for playing I'm not kidding when I say I was intimidated by this   

Now I (kinda) understand what you guys are going through when you ask someone trying to fix something to measure voltages and report back 

Yes.  You could look it up, or you could solve for X: 
8.76/12.80 = x/(x+6)
[/quote]

More homework from G1 

I tried it with the original equation and got a 13 so I looked it up and it said 10 so I retried it using a different denominator and got closer

You cannot view this attachment.

You cannot view this attachment.

 

Ok I wanted to turn in my homework for bonus points but I was like wow I better do the original assignment 
And yes I've seen the answers but it's been a while so here we go.
First I wanted to check a similar scenario on my bronco and I felt sorry for my hf meter so I verified some suspicions
Positive voltage
You cannot view this attachment.
Negative voltage
You cannot view this attachment.
I think I see 🙈 a trend

So here we go I filled out my worksheet and yes I was scared     
The way i did it in each case I started at ground then went from there

You cannot view this attachment.

Fun fact....one time I had a 36v trolling motor for my boat and reading about and trying to figure out how to connect it and the three 12v batteries blew my mind.

 

Ok I'm back with some results
It dawned on me that I had a decade resistor box so I was like hey that's pretty rad I can just dial in where voltage starts to roll off 

Unfortunately I looked at it and it only goes to 1000k (which I presume is one megaohm) 

Anyhow I started looking around and quickly found a 1M ohm resistor
You cannot view this attachment.

Ok cool so let's try 2M ohm
You cannot view this attachment.

Ok....there we go

I needed something in between so I looked around and found I think a 220k ohm resistor and added it to the 1M ohm 
You cannot view this attachment.

And the multimeter is already taking notice of the increased resistance...I think 

Man that's crazy awesome 

I was gonna comment on your soldering skills which look hella awesome 

For real looks like point to point wiring on an old tube amp.   

But then seeing that last post I'm floored 

Looks like you clearly have the dexterity skillz to accompany the acumen 

I'm way beyond impressed 

Ok I have a plan 

I'm gonna go back and increase the resistance in series with (+) and try to discern where voltage begins to drop.

I presume my meter has a 10 megaohm resistance so possibly it's gonna change at the 1 megaohm stage.

 

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 

You cannot view this attachment.

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

You cannot view this attachment.

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   
You cannot view this attachment.

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

  You cannot view this attachment.

 

What would RULE is a variac that not only allowed adjustable voltage but adjustable frequency as well  now that would be killer   

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

 

Awesome 

Watched the video and liked 

Love the tone at 00:52 

Nice and crunchy 

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

I finally finished a book
You cannot view this attachment.

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)
You cannot view this attachment.

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 
You cannot view this attachment.

And check it out
You cannot view this attachment.

 

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 

You cannot view this attachment.

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

And ya knew it was coming 

A parallel LCR circuit
You cannot view this attachment.

You cannot view this attachment.

It really helps to actually do stuff.  I wasn't getting the results I needed so I had to try and fix it.  Turned out I was using the 1k resistor that was called for previously when I fact a 100k resistor was needed.