It was rainy day, I was driving my family to some party when I got a call from my friend who told me that there is one Amiga 500 on second-hand market. Something like that never happens in my city. I left my family on parking and start running. There it was, in the middle of the junk, Amiga 500 under heavy rain, dirty. It was so sad to see that. I took it into my hands trying to find a seller. Finally he approached and told me 10Eur. It is mine! Well, he could put any price I would still take it but he didn't know that. Later that day I got home and after some cleaning and drying powered the machine and it started to work without any problems. There is a question I dare to ask. Do you think that your modern phone or PC would be working after 27 years? Think not!
This Amiga 500 was used for creating Vampire 500 as we know it.
Amiga 500 S/N: 2169035 build in 1991.
Two days ago after more than 800 Vampire 500 V2 cards tested this machine finally died.
I was so sad but after brief investigation I found out that only DIP64 socket is broken and that all electrolytic capacitors needs to be replaced. So not huge task you may say but problem was to find original DIP64 socket and I had to use original one because of proper alignment of headers used in Vampire cards. Luckily I had some DIP sockets with different pitch but with same metal connectors inside. So I just took those replacing broken ones inside DIP64 socket.
Capacitors were another story. I live in the place where is very hard to find anything so most of the time you have to order online and patiently wait for 2 months to get the package. Often after so much waiting you realize that you didn't get what you paid for so you have to start all over again. Trick is to think in front what part you will need for some project you will be doing next year.
Over the weekend I found 2 shops in my country who could have what I need. One of them was in my city and another about 100Km away. I woke up early and visited my local shop who was closed at the time they should be working. Right about when I decided to have road trip they showed and sold me capacitors. Yes, they had them. I was lucky and persistent waited for over 2 hours for them to open the store.
Most of the capacitors on the motherboard were nice looking not showing any traces of damage. However measuring revealed that they should be replaced. Over the time capacitance and ESR values changed a lot.
On the left side of the picture above is original capacitor from motherboard rated at 100uF, 16V. Capacitance was lower and ESR value more than two times bigger than it should be. Right side of the picture shows replacement capacitor rated at 100uF, 25V with ESR 0.78OHM like it should be according to shown chart. In total 17 capacitors needed to be replaced.
Purpose of this article was to write down serial number of this Amiga because this is the machine who took so many beatings over past three years. It is the machine who gave us Vampire accelerator and bright future to the Amiga. It still lives and I hope that it will live for next 27 years.
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 UTC (61572 reads)
(comments? | Score: 1)
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.