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\title{\textbf{Commodore 1902A Repair}}
\author{Steak Electronics}
\date{}
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  \textbf{Commodore 1902A Repair}
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\includegraphics[scale=0.4]{../pics/DSCN1699.JPG}
\captionof{figure}{Commodore 1902A 14'' CRT Monitor}

\section{Overview}
The goal is to repair an old Commodore computer monitor. 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.

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Quite a bit of the Commodore 1902A TV circuitry (H sync, V sync, etc) is in a few ICs, according to the schematic.

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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. 

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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!

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\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 about 80 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.

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!}



\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}
\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}







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