Keyboard on Amiga 600 has a simple way of work regarding sending information's to the motherboard itself. Each key has a conductible contact made of rubber which shortness a contact on the keyboard membrane. Due to age of Amiga keyboards those conductibility problems are most common and hard to fix.
Needed materials & tools: Silicone tube Graphite pencil Benzinum medicinale (Petrol without S, Pb) Scalpel Plastic can lid Cotton sticks
Disassemble keyboard and using petrol and cotton sticks clean keyboard and key contacts.
1. Remove graphite from pencil and turn it into a powder using scalper.
2. In plastic can lid make mixture of silicon, petrol and graphite powder. Petrol will ensure that silicon will not dry fast so this will give us some more time to work. After petrol evaporates silicon will start to dry.
3. Using cotton sticks apply tin layer of mixture to the key contacts. After few hours mixture will dry.
Posted by majsta on Friday, September 12 2014 @ 14:30:41 CDT (24360 reads)
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Amiga R&R: Amiga 600 repair
Prepare to be amazed :)
Here is little tutorial how I repaired another one A600 motherboard. I buy this one as not working from ebay from man we all know It was 20 minutes job and more time was needed to publish this online All is done using just voltmeter and ohmmeter. Most important thing everything is filmed in process of investigation. Nothing is prepared and discovered earlier !!!
Here it goes:
1. What I did first is to visually check for cold solder joints and realized that some time ago in this A600 was some kind of accelerator. Since it is not standard option to add accelerator to A600 attaching something on CPU may damage CPU pins. So I solder back pins but it seems that was not the real problem. Again black screen
2. Then I checked voltages on CPU everything was fine.
3. After that I checked RESET and HALT pins of the CPU. Hm something held CPU in reset state. Where is the problem?
4. My first thinking was that maybe KB_RESET found on PIN 63 on the GAYLE is maybe low and that is the reason why GAYLE is blocking main CPU. And yes that signal is LOW so here we have reason why motherboard is not working. But then again why that line is low ?
5. So few minutes later and looking at the A600 schematics there it was possible cause for all the problems, little tiny, tiny thing called resistor. On the back side of the motherboard there it was pull up resistor R511D.
Few moths ago I purchased on Ebay as described "working in perfect condition Amiga 600 motherboard". I didn't opened package until today. I was surprised, something was wrong with motherboard, display turns purple, problems with IDE controller. After little investigation and visual checking of some components I discovered that something is wrong with Denise chip. Moving my hand over the Denise chip caused disturbance on my monitor so I was thinking it must be cold solder joint or micro fracture somewhere near the chip. In the same time I realized one disturbing fact "How much Amiga motherboards ended in garbage because some simple problems we could fix in few minutes". So this video shows how to discover cold solder joints on this specific chip without any additional tools. My soldering technique was not so professional because I needed to leave motherboard in specific position to get this on video.
There are number of things that go wrong with your Amiga mouse, but at most cases simplest solution is best one to fix something. Problem with this Amiga mouse was related to left and right mouse button so I decided to fix problem and replace two Tactile Switches. Those swiches are made in SPST technology who represents simplest type "on or off". But remember that you need to use dimensions of switches showed on images at the bottom of this page and it must be Through Hole version.
For some people like me it is hard to find complete Amiga system in white condition or with all original parts. So almost every part I found need some kind of repair or cleaning. For yellowed plastic parts you need to use solution of hydrogen peroxide and water. For best results you need to use highly concentrated hydrogen peroxide for medical use and add 30% of water to that solution. Please keep in mind that in most of the countries hydrogen peroxide is illegal for selling or usage because of his toxicity. There has been some reports of creating poisons and even bombs with it so in most countries governments decided to put hydrogen peroxide on black list. Also remember that if you order something like this from E-bay seller or somewhere else can drive you to the number of problems at the customs. At the stores you can find hydrogen gel who is stable release of hydrogen peroxide but he is not strong enough to help you for whitening. For this process of cleaning plastic parts you can use tablets for washing dishes machine and add it in solution of 10% water and 90% hydrogen gel. Remember that you can speed up the process if you expose your container with solution and buttons, clips and other plastic parts to the Sun or source of heat. But you must prepare yourself that this process can last for few days even weeks, depending of your solution. In some cases you may use sulfuric acid or even bleach but it is very dangerous to mix them together so wear glows and security glasses. If you found hydrogen peroxide somewhere you can expect best results in just few hours. For my project of whitening Amiga 600 plastic and keyboard I used hydrogen gel, water and tablets for washing dishes machine. But, before start take pictures of your Amiga from every corner because without them you can have lot of problems with assembly after you finish cleaning process. Here you can find pictures for different stages of cleaning and assembly Amiga 600.