Guidelines for my Classic Computer Collection

Table of Contents

    My interest in old computers and electronics started in my childhood when I used to tear apart almost every electronics gadget I could come by. My main interest was to try to understand how it was put together and how it worked. It was also a hunt for new exotic devices that I didn’t know the internals of.

    After I finished my education as an electronics engineer I understood much more about what was going on inside a computer and knew how to repair a lot of things. This led to my admiration and fascination of old and classic computers. I remember that I also used to tear old computers apart that I now deeply regret since I now understand what could have been done to repair them and how to use them instead of just saving a few spare parts from them.

    Now my main interest in collecting old computers is to collect special portable computers and try to get hold of some of the computers that I remember from my childhood, that I used to own myself or those I took apart for fun. 

    A funny story is that I have had this huge LCD module lying around in my parts bin in many years. I think I kept it in hoping someday I would learn to control it and display something on it. Many years later I realized that the display came from a Toshiba T1000 so I started the search to find one again. One day I found a T1000 online and my memory briefly remembered that I once had one looking similar. It was in working condition except for some dead horizontal lines on the display. In my search for trying to repair the display I took the computer apart and realized that I actually had a spare display already. After the display was changed with the one from my parts bin I started up the computer and was looking at a perfectly working display that I kept for so many years. Stupid me that I took the first T1000 apart in the first place.

    Another computer I remember taking apart was an Amstrad NC100 that actually worked and came with the users manual. I remember trying to follow one of the basic programming examples (without knowing anything about programming at the time) from the manual to program a small analog clock. I never got it to work right. Eventually I lost interest in the computer and didn’t know what to use it for so I thought it was cool to take it apart. And yes I also kept the display from this computer so I have it as a backup somewhere. 

    Keep focused

    Before I started to collect old computers in a more formal way as my hobby, I didn’t think much about what I liked and didn’t and what criteria I had for finding a computer interesting. I soon realized that I would rather prefer to have a few very interesting computers than a big pile of normal beige consumer desktop computers. I’ve also met people interested in something that was so big or they wanted to collect everything they came by so it took over all their space. That’s why I’ve been trying to formalize some criteria for which computers I find interesting.
    Have a look on this post Visit to the Radio Collection to see what I mean.

    Positive criteria

    • Self contained systems with built in display, keyboard and drive like portable, notebook, laptop and especially small handheld computers.
    • IBM Thinkpads and laptops, some older IBM desktop computers.
    • Computers based on Intel CPUs ranging from 8080, 8088, 8086, 80286, 80286, Pentium Pro up to PIII.
    • Motorola 68K, Zilog Z80 systems.
    • Special blade rack servers.
    • Accessories bundled with a computer, missing power supply is not a big problem.
    • Good cosmetic condition. It has to be in good condition.
    • Personally related (if I previously owned a similar model).
    • Historical importance.
    • Special features not seen in similar models of the same time period. E.g. smallest, fastest, lightest, build in printer, foldable keyboard or similar.
    • Preferably keyboard layout in Danish or English, not German

    Negative criteria

    • Consumer home computers like Amiga 500 and Commodore 64 are too mainstream.
    • Game consoles and handheld gaming devices.
    • Needs to be in a repairable condition; no broken display, damaged cabinet, motherboards damaged from acid corrosion from leaking batteries.
    • AMD, Intel Celeron CPU.
    • Consumer beige or silver desktops with CRT display.
    • Apple computers, maybe except for a G4 Cube which I think look cool.
    • Software, manuals, boxes and accessories without the computer they belong to.
    • Cabinets yellowed by sun or smoke.
    • The amount of computers cannot become an obsession or burden. They can not take over all the space of my workshop or storage room. 

    However I’m willing to ignore my criterias if I see a good bargain, that I’m able to sell again at a profit to fund other more interesting devices. Or if the device I’m interested in is only sold as part of a lot. 

    Other electronic gadgets of my interest

    • Small pocket televisions LCD or CRT 
    • Unique Sony portable devices; discman, walkman, watchman
    • Portable memory devices.
    • Wrist watches with special features like; camera, GPS, MP3, tv or similar from before smartwatches was a thing.

    Where to buy

    My preferred place to search for old computers is the Den Blå Avis (The Blue Newspaper, Danish version of eBay just not auctions). Instead of searching through the thousands of articles with computers I usually use the search agent so I get an email every time an article with a specific computer model name is put up for sale. I also post ads where I’m actively searching for a specific computer. If I find a seller that is selling some interesting items I usually also check the other items from this seller.

    For more exotic computers I have to reach out to eBay. But to me eBay has a lot of challenges. Most of the more rare computers are located in the USA so shipping and taxes are too expensive. Prices are also often ridiculously high because the seller thinks it is worth more than it is in reality. On the other side, if the price is fairly low, too many collectors want it and then the price goes up. Often if I end up winning an auction the price is way higher than I expected to pay. Okay I know you won’t get an Apple 1 or Altair 8800 unless you are willing to pay really big money. To make an overview of the actual value of a specific computer I list the sold items then I can see what has been sold in the past and get an idea of the price level.

    Recently Facebook Marketplace has begun to grow in popularity in Denmark but often it is just a repost of the same computer that is already on DBA. Facebook groups about vintage computers is also an option but most of the groups seem to be based in the USA, so shipping and taxes is the problem again.

    Another source where you can be lucky to find something interesting at a good price is at thrift stores, garage sales or flea markets. Often people just want to get rid of the old stuff and a good bargain can be made. However I haven’t seen much of interest in these places because most of the stuff is too new to be interesting.

    If you live in a larger city, chances are that you can find some old electronics devices thrown away as bulky waste (todo link). I did manage to find an old IBM ThinkPad once, but the chances are not very likely. 

    Before the awareness of data security and GDPR concerns, larger companies were also more likely to throw out their old computers in electronic containers. But I’m not sure this is the procedure anymore. 

    The last option that can be useful, is to let your family and network know about your passion for old computers. Maybe someone is about to throw out an old computer that could become a retro gaming machine. 

    How to avoid fraud

    When buying at DBA or Facebook Marketplace the usual accepted way is that the buyer pays for the item plus shipping before it is shipped. The buyer then has to trust the seller which in my case usually is okay because most people are honest, but I have been fooled.

    Of course it is annoying to lose one’s money but the worst thing is not getting the item that you had been hoping for and to get angry because another person has scammed you just to earn a small amount of money. In order to avoid fraud in the future I have defined some rules that I need to remember. Maybe you can learn something from them so you don’t have to experience the same thing.

    Background check
    When buying from DBA I only buy from sellers that are NemID validated. This means that the user has validated his/hers name and contact information through a Danish digital signature that is also used for net banking and login to public online services. I also make sure that the user hasn’t recently created the account but it needs to be older than a year. Often when people are cheating they create a new account, use a prepaid sim card, and avoid to validate their account. Then it is next to impossible to track the user.

    • I prefer to pick up costly items in person. I avoid to prepay things if they cost more than a certain number, otherwise I need to find someone that can pick it up in person if it is located far from me or I have to refuse to buy it. 
    • I often ask for extra images of specific details both to make sure that the item is as expected and described but also to make sure that the seller actually owns the product. And not just uses images downloaded from the internet. 
    • If the seller is insisting about transferring for the item right away, you need to be careful. 
    • Do a background check. Ask the seller for contact information and make a cross check with the DBA account, the name seen in Mobilepay and look it up on address search engines like in Denmark. If they do not match something is most likely wrong. 
    • When prepaying I prefer to use MobilePay instead of direct money transfer. Mobilepay is also validated against NemID so it is a little more safe than transferring to a bank account.
    • I newer ships internationally when selling anything on DBA. If the seller lives outside of Denmark he needs to find someone with a Danish address I can send it to. I will rather wait for a national buyer to show up than bother with internationally shipping.
    • Always contact the police if you are expiring fraud.
    • I need to avoid getting too excited because then I often forget about the rules above.


    It is typical to see the same kind of failures of the same models of computers. Sometimes it could be a bad design choice or weak components. 
    When I’m searching for a specific model I usually do some research to investigate the typical errors and see if I can find good ways to fix them. By doing this I can be lucky to buy a non working (cheap) computer and fix it myself.
    A good example of this is the Amstrad NC-100 that has a DC power supply plug with ground on the center pin and VCC on the outer ring. Usually on other equipment it is opposite. So if an unoriginal power supply is used it will damage the computer. Fortunately the computer is equipped with an internal fuse. After this fuse has been replaced the computer should work again.


    When I receive a “new” computer for my collection the first thing I do is to start cleaning it. Remove unwanted stickers, if needed remove the residual glue with alcohol, clean the exterior with a damp cloth with a little soap. For cleaning the display I always use a microfiber cloth without any detergent. Keyboards are often dirty and need careful rubbing to clean them. Older beige cabinets are prone to scratches from other plastic objects that leaves another color. This can be removed by using a magic sponge, but be careful because it contains an abrasive which will scratch the surface. 

    Power supply

    Often old laptops are sold without the power supply. Of course it is convenient to have the original power supply, but it is not a big problem if it is missing. The computer has a description on the bottom about voltage and amperage so a replacement power supply can often be found. The connectors are often the same barrel jack type but remember to look out for the polarity. 
    Internal power distribution boards that convert the incoming voltage like 12V to different voltages like 5V, 3.3V etc contain large capacitors. Those capacitors are proven to fail because of age. It is very important to inspect and replace bad capacitors, because they can short circuit. 


    Old liquid crystal displays were often connected to their driver circuit board by zebra conenctors. These connectors are very sensitive to dirt and moisture. A bad connection in this kind of connector will result in missing horizontal or vertical lines on the display. A very careful disassembly of the LCD unit and cleaning can sometimes save the display. 
    It is also important to protect old LCDs from high temperature, pressure and UV light since this can also break them.


    One thing is to hunt down a rare computer and restore it to work again. Another thing is how to store it afterwards to best protect it.
    Changing temperatures and humidity are some of the worst conditions to store old computer equipment in. This means that an uninsulated attic or shed is not a good place to leave them. The heat in the summer and cold in the winter will stress the components like circuit board, plastic cabinets, display, and movable mechanical parts. My workshop is in a heated basement. So the temperature is constant around the year and the humidity is not too high. 
    Another very important concern about protecting old computers is to remove the internal battery and the backup battery for RTC and memory. These batteries have a limited lifetime and after that they are very likely to leak their acid contents. A motherboard damaged by acid can be very hard or impossible to repair. But by removing all batteries this is easy to avoid.
    Hard disk drives in old computers is another typical failure. The disk consists of multiple mechanical precision parts. Under normal circumstances it can work for a long time. The problem arises when the computer is left for a long time. Then the oil in the bearings can dry out and the magnetic head can get stuck on the surface of the platter.

    Plastic cabinets

    When plastic gets old it can become brittle. This means that the cabinet of the computer will break more easily than when it was new. There isn’t much to do about this problem except to be careful about the computer and to store it under the best conditions. 
    I have a few laptops that are missing the covers over the battery compartment or for the back connectors. I have an idea about 3d printing replacements for them sometime. Thingiverse is a great place to look for 3d models of spare parts. I found some keyboard feet for my Compaq Portable III that I tried to print. 
    Another problem with cabinets, this is almost unique to IBM Thinkpads, is that the cabinet is covered in rubber paint, that gives the surface a nice and soft finish that was supposed to be scratch resistant. The problem is that when the surface paint gets old it often gets extremely sticky and falls off.   
    I’m working on a IBM N51 SX where the entire top cover was exposed with the plastic surface because the rubber paint had fallen off. I’m about to scrape off all of the old surface to repaint it with a similar product.

    For a great article about this topic have a look at this How to Preserve Vintage Electronics guide.