PSU

Beaglebone_Blacks/docs/notes

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+took a look at this
+
+may be power regulator
+
+or may be something downstream
+
+it turns off for a second, then turns off. 
+
+hard to tell what is the problem.
+
+need to check all voltage rails when this is powered on.
+
+note that I found you can hit the power button to activate the vreg. but 
+this might be dangerous to hit repeatedly.
+
+let's try replacing the vreg, as I want an excuse to use my hot air station
+
+it's possible someone just gave it too much power.
+
+https://www.eevblog.com/forum/repair/could-i-repair-a-beaglebone-black-that-had-was-fried-by-the-wrong-adapter/
+
+hehe, they say don't bother fixing. Wow...
+
+
+Steps for this:
+Attempt replacement of vreg
+if that doesn't solve it, likely something downstream.
+connect to power rails, with PSU, and watch what heats up with iso alcohol.
+
+I have 4 or 5 of these beagles, so I only need to find it once. In fact, maybe 
+I should just skip to the inserting the Power supply in. there are a few 0805
+caps that are relatively easy to tap into...
+The board files are allegro, and I don't run win but 
+the schematic shows cap labels, so this is probably the best plan of attack.
+If I don't find anything heating up, then it would point to the power supply...
+
+Let's do that. 
+
+
+EDIT: testing all 4 beagles
+
+1 works, it appears. 
+1 turns on all 4 status leds, but no blinks. 
+
+2 have a brief led light on power reg, but then off. protection circuitry.
+
+I found 1 of them with a blown resistor on the ethernet shield to digital ground.
+it was a 0.1 ohm resistor. 
+
+I found 2 of the 2 with brief led lights to have a cap (3.3v rail) at 12 ohms. The others
+are 400 ohms. This was mentioned on forum. Probably someone put 12v on the input, and blew the 10v
+caps... flawed design, i think.
+
+I'm going to remove those caps first. off to the hot air station
+
+i should buy some 10uf 0805. i only have through hole and 1uf 0805 (though in a project
+bag there might be one somewhere...)
+
+After replacing cap, there's still 12 and 5 ohms on those respectively.
+So it wasn't the caps, but something on the rail. Looks like the 3v3 rail is the only 
+rail that has the short, per the other caps, didn't give me any unusual resistance, and
+also 3v3 is the one you would expect to be shorted (main v rail).
+
+can't find c16, which is on rtc. I need allegro to do layout searching
+
+3v3 goes into 
+main CPU (arctic)
+
+usb host tps2051
+
+SPI board id
+24lc32
+
+lan adapter (3v3b)
+
+HDMI (3v3b)
+
+and some 74 logic.
+
+
+I think the cpu is the issue. Let's disconnect R14, and see if power rail boots.
+there's two inputs. one is where r14 is, another is on USB. Hopefully I don't
+have to track down usb input. don't have layout.
+
+removed R52, and R14, but it's still shorted. 
+I believe the USB input to CPU is causing this. There aren't many other things it could be
+
+EDIT: looks like the 74 logic here is max 6.5 volts or so. could also be that.
+
+lets try to track down the short with the 6 digit dmm
+
+NOTE: there are two distinct 3v3 rails a and b
+
+3v3B comes from TL5209
+
+that is enabled after 3v3A is turned on.  (see notes in schematic updates)
+
+C20 on 3v3b looks to be 0.4K ohms, so OK.
+
+Must be 3v3a, which doesn't have much. 
+
+Nice idea, to separate 3v3 rails.
+
+based on my tracking with the 6 ohm dmm
+
+i found the lowest resistance somewhere around 5.5ohms in between the cpu and the ddr
+
+the ddr is 3v3b, so it must be the cpu.
+ let's remove hte cpu, and see if power rails start.
+
+removed CPU. first bga removal for me.
+
+And sucess. The low resistance on C16 is now 0.4K ohms. So the CPU is the weak point.
+I guess this means by design, of the bbb, I will be doing some hot air bga soldering.
+it must be gods will. (ti's will)
+
+
+
+
+I removed the second bga, but this time, I pulled some pads. Of course you can
+pull pads on a bga... May not be repairable, but lesson learned.

Beaglebone_Blacks/resources/BeagleBone-Black

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+Subproject commit 29f53596a2d88222e65fe19a7434f78d18c18711

Commodore_1902A_Monitor/docs/11.aux

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+\relax 
+\@writefile{lof}{\contentsline {figure}{\numberline {1}{\ignorespaces Commodore 1902A 14'' CRT Monitor\relax }}{1}}
+\@writefile{toc}{\contentsline {section}{\numberline {1}Overview}{1}}
+\@writefile{toc}{\contentsline {section}{\numberline {2}Work Log}{2}}
+\@writefile{toc}{\contentsline {subsection}{\numberline {2.1}We require more resources... (Starcraft 2 reference)}{2}}
+\@writefile{lof}{\contentsline {figure}{\numberline {2}{\ignorespaces Computer Monitor Troubleshooting and Repair\relax }}{3}}
+\@writefile{lof}{\contentsline {figure}{\numberline {3}{\ignorespaces Second Page. Right from the start the book is easy to read and approachable.\relax }}{4}}
+\@writefile{toc}{\contentsline {subsection}{\numberline {2.2}Errors on the Schematic}{4}}
+\@writefile{lof}{\contentsline {figure}{\numberline {4}{\ignorespaces Schematic lists ICs with numbers that...\relax }}{5}}
+\@writefile{lof}{\contentsline {figure}{\numberline {5}{\ignorespaces Differ on the actual layout diagram. Repairman beware!\relax }}{5}}
+\@writefile{toc}{\contentsline {subsection}{\numberline {2.3}Getting the Monitor ready for the repair attempt}{6}}
+\@writefile{toc}{\contentsline {subsection}{\numberline {2.4}Repair Attempt}{6}}
+\@writefile{toc}{\contentsline {section}{\numberline {3}References}{6}}

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Commodore_1902A_Monitor/docs/11.tex

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+
+\documentclass[11pt]{article}
+%Gummi|065|=)
+\usepackage{graphicx}
+\usepackage{caption}
+\title{\textbf{Commodore 1902A Repair}}
+\author{Steak Electronics}
+\date{}
+\begin{document}
+
+%\maketitle
+\begin{center}
+  \textbf{Commodore 1902A Repair}
+  \end{center}
+%\vspace{0.2in}
+
+\includegraphics[scale=0.4]{../pics/DSCN1699.JPG}
+\captionof{figure}{Commodore 1902A 14'' CRT Monitor}
+
+\section{Overview}
+The goal is to repair an old Commodore CRT monitor. This is not a computer monitor, but a strange hybrid TV/Commodore only mode CRT. Normal CRTs take input of RGB, while this one takes composite video (like a television), as well as RGBI\footnote{This is one of the things I learned here, the difference between a computer monitor and a television. TVs take in NTSC/PAL/SECAM analog video. Computer monitors take in the signals already split up (VGA). However, this monitor does a hybrid of both, being made before VGA was commonplace.}. This particular monitor, the 1902A has three inputs. One for composite, one for S-Video (essentially connected to same circuitry as composite) and one for RGBI mode.
+
+Currently, the monitor has errors on composite input / S-video. There are no errors on the RGBI input.
+
+\tableofcontents
+
+\section{Work Log}
+I picked up an old HP TV service manual (6945A) for this project. I am not knowledgable about televisions, but the more I read, the more I think I can handle this. I have also the manual for the monitor, though it is quite a bit sparse, comparably.
+
+\vspace{0.2in}
+
+
+Quite a bit of the Commodore 1902A TV circuitry (H sync, V sync, etc) is in a few ICs, according to the schematic.
+
+\vspace{0.2in}
+
+The waveforms in the Commodore manual were created with a (standard?) NTSC test signal, the \textbf{10 bar gated rainbow pattern signal}. I am currently researching how to generate that myself, without forking out the cash for a video tester (Cheapest I saw the other day was \$70. I wouldn't pay more than \$20. 
+
+\vspace{0.2in}
+
+From a brief search, most people have only setup rough test signals with uCs that do either NTSC or PAL, but not necessarily the full 10 bar gated test signal. Instead only a passable working signal, to verify video output, seems to be par for the course. I might be out of luck!
+
+\vspace{0.2in}
+
+\subsection{We require more resources... (Starcraft 2 reference)}
+
+I reviewed this page:
+
+http://www.repairfaq.org/sam/monfaq.htm\#monsugref
+
+Which many will recognize as the gargantuan repair faq website.\footnote{I find text heavy websites like this, quite incomprehensible, to be honest. How much better the site would be, if it was a book. I know I'm not the only one that thinks this way (e.g. Bill Waterson said he prefers actual paper of his comics to a computer screen), but yet websites continually seem to post article after article, after blogpost, after blogpost, of which I will not take the time to click through. Websites are infinitely inferior to books, for any significant amount of text. This is why twitter (and not booker) is so successful. Am I wrong in thinking this, or are the search engines skewing how much people actually read these ``blog'' websites?} I'm going to purchase a book they mention:\\
+\textbf{Computer Monitor Troubleshooting and Repair} - Joe Desposito and Kevin Garabedian
+
+\includegraphics[scale=0.4]{../pics/DSCN1864.JPG}
+\captionof{figure}{Computer Monitor Troubleshooting and Repair}
+
+which cost me a whole \$6.00 from a used book store online. While the HP book was helpful, it is for a B\&W CRT lacking any colour related circuitry, and I need something with more practical repair advice. The HP tech book, is also dry, which means it assumes you understand a lot of the mechanics already.
+
+After reading some pages of the computer monitor repair book (recommended as I said by repairfaq.org) I can say it is a good book, and would recommend it to others. it lacks any concrete material on TV Signal encode/decoding, it being a book on computer monitors (which have RGB signals split up by default, via the VGA connector), it remains a straightforward and down to earth book on CRTs. An obsolete gem. The book uses three computer monitor schematics for its instructions, showing different approaches to similar circuits. A schematic for a Magnavox, NEC, and Samtron VGA Computer monitor are covered in explicit detail. 
+
+Here's an example page, for those readers interested in a preview:
+
+\includegraphics[scale=0.4]{../pics/DSCN1865.JPG}
+\captionof{figure}{Second Page. Right from the start the book is easy to read and approachable.}
+
+\subsection{Errors on the Schematic}
+After reviewing the Commodore 1902A service manual, I noticed that the layout design doesn't match up 1:1 with the schematic... On the same service manual! Is this an honest mistake, or a reluctance to give repairmen the real schematic, or a limitation of time and money? Who knows. In any case, I found an intial error looking at the early Composite signal input.
+
+\includegraphics[scale=0.4]{../pics/DSCN1866.JPG}
+\captionof{figure}{Schematic lists ICs with numbers that...}
+
+
+\includegraphics[scale=1.67]{../pics/DSCN1868.JPG}
+\captionof{figure}{Differ on the actual layout diagram. Repairman beware!}
+
+\subsection{Getting the Monitor ready for the repair attempt}
+I setup the monitor on the bench this evening, desoldering the can on the bottom, and resoldering on of the hi voltage wires I had to cut in order to disassemble it. The pictures I took helped a lot in finding where everything went. In particular there are two ground pins that are easily confused. One is for the high voltage area, the other for the CRT board.
+
+\vspace{0.2in}
+
+Reviewing the schematic, I traced out a bit more of what goes where, and will start by checking the voltage levels. But first, to get a signal source.
+
+\vspace{0.2in}
+
+Like the Sony PVM\footnote{Sony PVMs are a brand of television that retro video game players make a big fuss about (circa 2010's). To be honest, I have 2 of them, and I don't find them worth the hype. Especially not RGB mode. Any modest CRT was good enough when you were a kid, and any modest CRT is good enough as an adult. It's the gameplay that matters. Don't believe the hype!}  I've taken apart and attempted to repair previously, this CRT is not easy to service. Accessing the bottom of the board while it's powered on is a balancing act. But I have managed to get it on the bench, and after reading a bit more of the Computer Monitor Troubleshooting and Repair book, (and possibly a separate book dedicated for Television, to cover the decoding) I will start the repair.
+
+\subsection{Repair Attempt}
+I plugged a PS1 into the television, to find that the picture was working.
+
+
+\section{References}
+
+\textbf{Books}
+\begin{itemize}
+\item Art of Electronics 3rd Edition (Horowitz, Hill): Appendix I - Television.
+  \item Computer Monitor Troubleshooting and Repair - Joe Desposito and Kevin Garabedian
+  \end{itemize}
+
+\textbf{Video}\footnote{Disclaimer: Youtube is bad. Please avoid when possible in favor of a video site that is not a centralized, censored, monopoly.}
+\begin{itemize}
+\item Retro Game Mechanics Explained:  https://www.youtube.com/channel/UCwRqWnW5ZkVaP\_lZF7caZ-g
+  \\(the SNES section has some well produced CRT video explanations).
+\end{itemize}
+
+
+
+
+
+
+
+\end{document}
+

Commodore_1902A_Monitor/docs/11.tex~

@@ -0,0 +1,109 @@
+
+\documentclass[11pt]{article}
+%Gummi|065|=)
+\usepackage{graphicx}
+\usepackage{caption}
+\title{\textbf{Commodore 1902A Repair}}
+\author{Steak Electronics}
+\date{}
+\begin{document}
+
+%\maketitle
+\begin{center}
+  \textbf{Commodore 1902A Repair}
+  \end{center}
+%\vspace{0.2in}
+
+\includegraphics[scale=0.4]{../pics/DSCN1699.JPG}
+\captionof{figure}{Commodore 1902A 14'' CRT Monitor}
+
+\section{Overview}
+The goal is to repair an old Commodore CRT monitor. This is not a computer monitor, but a strange hybrid TV/Commodore only mode CRT. Normal CRTs take input of RGB, while this one takes composite video (like a television), as well as RGBI\footnote{This is one of the things I learned here, the difference between a computer monitor and a television. TVs take in NTSC/PAL/SECAM analog video. Computer monitors take in the signals already split up (VGA). However, this monitor does a hybrid of both, being made before VGA was commonplace.}. This particular monitor, the 1902A has three inputs. One for composite, one for S-Video (essentially connected to same circuitry as composite) and one for RGBI mode.
+
+Currently, the monitor has errors on composite input / S-video. There are no errors on the RGBI input.
+
+\tableofcontents
+
+\section{Work Log}
+I picked up an old HP TV service manual (6945A) for this project. I am not knowledgable about televisions, but the more I read, the more I think I can handle this. I have also the manual for the monitor, though it is quite a bit sparse, comparably.
+
+\vspace{0.2in}
+
+
+Quite a bit of the Commodore 1902A TV circuitry (H sync, V sync, etc) is in a few ICs, according to the schematic.
+
+\vspace{0.2in}
+
+The waveforms in the Commodore manual were created with a (standard?) NTSC test signal, the \textbf{10 bar gated rainbow pattern signal}. I am currently researching how to generate that myself, without forking out the cash for a video tester (Cheapest I saw the other day was \$70. I wouldn't pay more than \$20. 
+
+\vspace{0.2in}
+
+From a brief search, most people have only setup rough test signals with uCs that do either NTSC or PAL, but not necessarily the full 10 bar gated test signal. Instead only a passable working signal, to verify video output, seems to be par for the course. I might be out of luck!
+
+\vspace{0.2in}
+
+\subsection{We require more resources... (Starcraft 2 reference)}
+
+I reviewed this page:
+
+http://www.repairfaq.org/sam/monfaq.htm\#monsugref
+
+Which many will recognize as the gargantuan repair faq website.\footnote{I find text heavy websites like this, quite incomprehensible, to be honest. How much better the site would be, if it was a book. I know I'm not the only one that thinks this way (e.g. Bill Waterson said he prefers actual paper of his comics to a computer screen), but yet websites continually seem to post article after article, after blogpost, after blogpost, of which I will not take the time to click through. Websites are infinitely inferior to books, for any significant amount of text. This is why twitter (and not booker) is so successful. Am I wrong in thinking this, or are the search engines skewing how much people actually read these ``blog'' websites?} I'm going to purchase a book they mention:\\
+\textbf{Computer Monitor Troubleshooting and Repair} - Joe Desposito and Kevin Garabedian
+
+\includegraphics[scale=0.4]{../pics/DSCN1864.JPG}
+\captionof{figure}{Computer Monitor Troubleshooting and Repair}
+
+which cost me a whole \$6.00 from a used book store online. While the HP book was helpful, it is for a B\&W CRT lacking any colour related circuitry, and I need something with more practical repair advice. The HP tech book, is also dry, which means it assumes you understand a lot of the mechanics already.
+
+After reading some pages of the computer monitor repair book (recommended as I said by repairfaq.org) I can say it is a good book, and would recommend it to others. it lacks any concrete material on TV Signal encode/decoding, it being a book on computer monitors (which have RGB signals split up by default, via the VGA connector), it remains a straightforward and down to earth book on CRTs. An obsolete gem. The book uses three computer monitor schematics for its instructions, showing different approaches to similar circuits. A schematic for a Magnavox, NEC, and Samtron VGA Computer monitor are covered in explicit detail. 
+
+Here's an example page, for those readers interested in a preview:
+
+\includegraphics[scale=0.4]{../pics/DSCN1865.JPG}
+\captionof{figure}{Second Page. Right from the start the book is easy to read and approachable.}
+
+\subsection{Errors on the Schematic}
+After reviewing the Commodore 1902A service manual, I noticed that the layout design doesn't match up 1:1 with the schematic... On the same service manual! Is this an honest mistake, or a reluctance to give repairmen the real schematic, or a limitation of time and money? Who knows. In any case, I found an intial error looking at the early Composite signal input.
+
+\includegraphics[scale=0.4]{../pics/DSCN1866.JPG}
+\captionof{figure}{Schematic lists ICs with numbers that...}
+
+
+\includegraphics[scale=1.67]{../pics/DSCN1868.JPG}
+\captionof{figure}{Differ on the actual layout diagram. Repairman beware!}
+
+\subsection{Getting the Monitor ready for the repair attempt}
+I setup the monitor on the bench this evening, desoldering the can on the bottom, and resoldering on of the hi voltage wires I had to cut in order to disassemble it. The pictures I took helped a lot in finding where everything went. In particular there are two ground pins that are easily confused. One is for the high voltage area, the other for the CRT board.
+
+\vspace{0.2in}
+
+Reviewing the schematic, I traced out a bit more of what goes where, and will start by checking the voltage levels. But first, to get a signal source.
+
+\vspace{0.2in}
+
+Like the Sony PVM\footnote{Sony PVMs are a brand of television that retro video game players make a big fuss about (circa 2010's). To be honest, I have 2 of them, and I don't find them worth the hype. Especially not RGB mode. Any modest CRT was good enough when you were a kid, and any modest CRT is good enough as an adult. It's the gameplay that matters. Don't believe the hype!}  I've taken apart and attempted to repair previously, this CRT is not easy to service. Accessing the bottom of the board while it's powered on is a balancing act. But I have managed to get it on the bench, and after reading a bit more of the Computer Monitor Troubleshooting and Repair book, (and possibly a separate book dedicated for Television, to cover the decoding) I will start the repair.
+
+
+\section{References}
+
+\textbf{Books}
+\begin{itemize}
+\item Art of Electronics 3rd Edition (Horowitz, Hill): Appendix I - Television.
+  \item Computer Monitor Troubleshooting and Repair - Joe Desposito and Kevin Garabedian
+  \end{itemize}
+
+\textbf{Video}\footnote{Disclaimer: Youtube is bad. Please avoid when possible in favor of a video site that is not a centralized, censored, monopoly.}
+\begin{itemize}
+\item Retro Game Mechanics Explained:  https://www.youtube.com/channel/UCwRqWnW5ZkVaP\_lZF7caZ-g
+  \\(the SNES section has some well produced CRT video explanations).
+\end{itemize}
+
+
+
+
+
+
+
+\end{document}
+

Commodore_1902A_Monitor/docs/11.toc

@@ -0,0 +1,7 @@
+\contentsline {section}{\numberline {1}Overview}{1}
+\contentsline {section}{\numberline {2}Work Log}{2}
+\contentsline {subsection}{\numberline {2.1}We require more resources... (Starcraft 2 reference)}{2}
+\contentsline {subsection}{\numberline {2.2}Errors on the Schematic}{4}
+\contentsline {subsection}{\numberline {2.3}Getting the Monitor ready for the repair attempt}{6}
+\contentsline {subsection}{\numberline {2.4}Repair Attempt}{6}
+\contentsline {section}{\numberline {3}References}{6}

Dell_Optiplex_780/docs/notes

@@ -0,0 +1,22 @@
+Some heat damage on the PSU.
+
+Don't know where the fault is.
+
+-12V rail is -10.6V.
+
+Need to test ATX psu with proper equipment. 
+
+Need to replace CPU, and try booting.
+
+Need to see if problem lies in CPU, Motherboard, or PSU.
+
+Not worth my time right now.
+
+Putting aside.
+
+
+
+
+Note: I did check a bit of the ATX PSU. I found a picture at
+http://www.pavouk.org/hw/atxps.png
+Which shows a similar supply. When in doubt, find a similar schematic.