Pages: [1] 2   Go Down

Author Topic: Are there any tech geniuses who can explain how this circuit works?  (Read 682 times)

N1AUP

  • Member
  • Posts: 538

https://www.ameradio.com/doc/Astron%20RS-35A%2C%20RS-35M%20schematic.pdf|

I would like to start a streaming ham radio class that can teach hams some electronic basics / troubleshooting.  I'd like to start with a regulated, non-switching supply.

https://www.ameradio.com/doc/Astron%20RS-35A%2C%20RS-35M%20schematic.pdf

I know what some of this does, but would like to find an electronics expert that can help me understand how the circuit works. 

Is there anyone who can help?

Thanks
Logged

AI5BC

  • Posts: 456
    • HomeURL
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #1 on: January 22, 2023, 04:29:04 PM »

Now that is funny. You have no clue how a very simple circuit works and want to teach other hams.
Logged

W0CKI

  • Member
  • Posts: 637
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #2 on: January 22, 2023, 04:48:55 PM »

Now, that’s not. Standard a hole response from BC
Logged

W1VT

  • Member
  • Posts: 6071
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #3 on: January 22, 2023, 05:05:34 PM »

The Art of Electronics by Horowitz and Hill has an excellent discussion of how the 723 regulator works.  It has been in print for decades so plenty of used copies are available.

Logged

K3UIM

  • Member
  • Posts: 2145
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #4 on: January 22, 2023, 05:43:42 PM »

BC: I've taught a few novice classes (too many years ago) and have been asked questions that made me stop and think also. Having a license doesn't mean we know it all. It's a devil in the wood pile that we hope never rears its' ugly head. Keep on keeping on AUP!
"Red-faced" Charlie
LOL
Logged
Charlie. K3UIM
Where you are: I was!
Where I am: You will be!
So be nice to us old fogies!!

AC2EU

  • Member
  • Posts: 2793
    • McVey Electronics
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #5 on: January 22, 2023, 06:38:15 PM »

It's a pretty standard circuit .
The 723 voltage regulator Ic is driving a couple of "pass" transistors to supply enough current to the load.
If this is too tricky for you, I don't know how you expect to teach others?
You might want to hit the books first.

AI5BC

  • Posts: 456
    • HomeURL
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #6 on: January 22, 2023, 07:20:48 PM »

It's a pretty standard circuit .

If this is too tricky for you, I don't know how you expect to teach others?
He can't, that was my point. Now he wants to teach others on the new idiot's bible, YouTube. You can't make this stuff up. 
Logged

K7MEM

  • Member
  • Posts: 1058
    • JavaScript Electronic Notebook
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #7 on: January 22, 2023, 09:21:15 PM »

IMHO, if you are going to attempt teaching, start with a much simpler power supply. The ua723 regulator has been around for a very long time. I have no problem understanding it, and have used it in designs many times. However, a power supply starts at the transformer. Start with the transformer, a couple of diodes, and some filter capacitors. For example: Basic Power Supply Design. Know why the parts are specified the way they are. Then branch out into regulators. I'm sure there are other web pages that discuss power supply design.
Logged
Martin - K7MEM
http://www.k7mem.com

N1AUP

  • Member
  • Posts: 538
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #8 on: January 23, 2023, 01:17:35 AM »

1.  I built a 13.8 volt DC power supply years ago.  The transformer had two pins, outputting about 18 volts.  That fed a bridge rectifier. 

This Astron has multiple pins of output on the transformer, and it appears that they are not using a bridge rectifier. 

Why?
Logged

G3RZP

  • Member
  • Posts: 2254
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #9 on: January 23, 2023, 01:41:21 AM »

I have always found the 723 to be very prone to picking up any RF that's around and going mad as result.
Logged

N1AUP

  • Member
  • Posts: 538
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #10 on: January 23, 2023, 02:10:41 AM »

BC: I've taught a few novice classes (too many years ago) and have been asked questions that made me stop and think also. Having a license doesn't mean we know it all. It's a devil in the wood pile that we hope never rears its' ugly head. Keep on keeping on AUP!
"Red-faced" Charlie
LOL

Here's the problem with people who blithely advise you to "read the manual" or "read the textbook".

Most of this stuff was written by people who understand the topic, but are not very skilled at explaining it.  Computer books are the worst offenders.  The authors don't have any ability to comprehend where a student's understanding happens to be, and even less skill at taking that level of understanding and expanding it.  The authors assume that the student understands what they do, so much of what's there goes over the head of the person who wants to learn.  Add to the reality that too many engineers never learned to write, and you have a major problem.

It's rare to find someone who understands a topic, and also has the skill to properly explain and educate, and communicate.

I'm firmly convinced that engineers should spend two years studying liberal arts and especially English before spending time learning the techy stuff.  I also believe that liberal arts people should get a solid grounding in math, and tech. 

 
Logged

WW5F

  • Posts: 451
    • HomeURL
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #11 on: January 23, 2023, 03:09:56 AM »

You don't really learn anything until you have to teach it. 

Learned how to teach many times in my life.  Thought it would always be easy to put together a lesson plan for stuff I'd been doing my whole life until I started putting lesson plans together to teach the stuff I'd been doing my whole life.  Never realized how little I knew about what I was about to teach until I had to teach it.  So called "smart" people usually skip over a lot of stuff and assume some stuff is so obvious, it doesn't need to be stated.  This is the main reason some teachers get so frustrated when students STILL DON'T UNDERSTAND what they're saying.

First, you have to answer all the questions you raise by yourself when trying to figure something out BY YOURSELF.  Then, when light bulbs start spontaneously lighting above your brain, you realize there are things about it that are SO OBVIOUS to the person/people who originally put it together, they didn't think it was necessary to restate it.  THIS, is what you have to explain to your students.

My first impression of this astron schematic is that the transformer has two outputs.  The inside taps (lower voltage) go to a half wave rectifier, followed by a filter capacitor and then to the pass transistors.  This provides the regulated output of 13.8 volts at up to 35 amps (higher current).  The outside taps (a little higher voltage) also go through a half wave rectifier and filter capacitor and is then regulated by the UA723 (lower current) to the bases of the pass transistors (for higher current through them).  My next step would be to start looking at the specifications of the UA723 to start figuring out all the reasons for all those other little discrete components around the UA723.

But I don't fix power supplies any more and I'll never teach anything about power supplies again.

Extra vignette, supplied to you free of charge...  What I've learned about math:  You don't really learn algebra until you're in calculus.  And you don't really learn calculus until you learn its disjointed history, which started with geometry.  I'm 60 years old and didn't figure this out until a few months ago.  I think I'm now, finally, ready to start teaching calculus.
Logged

KF6QEX

  • Member
  • Posts: 788
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #12 on: January 23, 2023, 03:40:24 AM »

"It's rare to find someone who understands a topic, and also has the skill to properly explain and educate, and communicate."

There are a lot of lousy teachers out there.
But there are also a lot of lousy students.




Logged
sdrawkcab daer tseb si txet sihT

K9CTB

  • Member
  • Posts: 27
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #13 on: January 23, 2023, 04:05:33 AM »

This schematic is on the high end of basic electronics knowledge and skill course.  I'd recommend attending such a course if you want to teach this sort of circuitry on a component level.  It might be better to present it on a block-diagram level, since that's all that would be needed to pass a modern amateur radio license test.  A good (if limited) instructor could use the block diagram approach to "ignite a fire" in the student to learn more ... or to take such a basic course him or herself.  JMHO.
Logged

W1VT

  • Member
  • Posts: 6071
Re: Are there any tech geniuses who can explain how this circuit works?
« Reply #14 on: January 23, 2023, 04:23:36 AM »

One of the co-authors of the Art of Electronics is a ham, W1HFA.  I remember a memory keyer article he wrote for QST.
Logged
Pages: [1] 2   Go Up