Powering Up An Original Apple I After Three Decades In A Museum

An Apple I hooked up to lab power supplies and a monitor

The Apple I is the stuff of legend. Designed and marketed in 1976 by Steve Wozniak and Steve Jobs, it was the very first product released by what would become today’s multi-trillion-dollar manufacturer of iPhones and iMacs. With about 60 original ones known to exist today, prices at auction are commonly in the $300,000 range, while confirmed working ones are even more valuable.

The Heinz Nixdorf Museumsforum (HNF), a computer museum in the German city of Paderborn, is fortunate enough to have an original Apple I in its collection. Although it has been there since 1996, it was always on static display and had never been powered on. In fact, it was unknown whether it would even work, and with it being the most valuable exhibit in the entire museum, simply firing it up would be a seriously risky project.

But computers are meant to be used, so museum director [Jochen Viehoff] decided to take the plunge and attempt to get the classic Apple to run again. In the four-part video series embedded below, [Jochen] explains the history of Apple’s first product and the steps he took to bring it back to life. This began with taking it out of its bullet-proof display case and bringing it upstairs to the museum’s workshop.

In order to make a complete system, HNF staff also dug up a period-correct keyboard as well as a slightly newer Apple monitor that could display the 60 Hz composite video output. Hooking up an original power supply would have been way too risky, because a single mistake or malfunction could send their top exhibit up in flames. Instead, they used a set of lab power supplies with a programmable current limit; this way, even a dead short on the PCB would not result in any serious damage.

Not that there were any shorts: after a bit of fiddling with the keyboard and adjusting the video output level, the 45-year-old computer came to life and began to respond to commands. With just 256 bytes of ROM, its default feature set is rather limited, but the computer duly executed a simple “Hello, World” program writen in 6502 machine code. It thereby joined the elite club of confirmed working Apple I’s, of which there are thought to be about twenty.

If you haven’t got $300,000 to spare but would still like to try your hand at programming the Apple I, you’ll be happy to hear that you can get a modern copy at a far more affordable price. And if all that classic hardware is too fiddly for you, you might want to try implementing the Apple I on an FPGA.


27 thoughts on “Powering Up An Original Apple I After Three Decades In A Museum

  1. Great post. I just wonder, for how long the electrolytic capacitors will still last before exploding.
    My Beep is in the garage – but i hesitate to switch it on after about 40 years …

    1. The typically they would last about 20-30 years before failure (some may be longer) irregardless if they are in a device that is powered on or stock sitting on a shelf as unused. Their capacitance will change with age, so you should replace all electrolytic capacitors.

      There are tutorials and videos online showing the parts to replace (search for “bbc computer recapping”). It is typically the X2 Safety Capacitors (which are not electrolytic) in that power supply that will fail short circuited and kill the board.

    2. electrolytic capacitors made before around 1992 are most of the time fin, but reformatting them with a series resistor is advised. after 1992, all bets are off. I just fired up a old tone generator from 1952 and it works first time (philips GM2308) but ymmv.

  2. Wow. Yet “being the most valuable exhibit in the entire museum” is not really correct, may be “one of the” as there is a CRAY-2 as well, which I would range beyond 300k ;-)

    1. Looking at the video one electrolytic capacitors shows 7630L which could be 1976 week 30 which would make sense. The first boards shipped 1976-04-11 and last ones shipped were 1977-09-30. So I would guess that yes they are original type 36D can-type capacitors. Would they still be 2400UF 25 VDC probably no where near that now. Sprague Electric is now a subsidiary of Vishay, and the parts are still available, so there is a datasheet for that part which gives a “Useful life at 85 °C” of 500 hours! which should (using the 10°C rule or Arrhenius Equation) be about 32000 hours at 25°C.

      1. My dad has a couple original IBM PCs in the basement, from ’81, and I’ve been meaning to get around to firing one up. Now I’m wondering what precautions I should take if I do.

        1. If I was going to power on a computer from 81, I would visually inspect all the electrolytic capacitors for bulging. Check that the RTC (realtime clock) battery had not leaked over the board. Some machines used to use 10+ year lithium batteries (which might have been non-rechargeable lithium manganese dioxide), you would probably need to replace that. Some machines used button cells for the RTC backup power. The electrolytic capacitors if not bulging will probably work, but their tolerance will be much worse. Some people suggest de-soldering them all and placing a low value resistor in series in case they have shorted, but if you are going that far it is not much further to remove and testing them all, or just replacing them all.

          The real danger is probably from the X Safety Capacitors inside the PSU, you would need to open that and inspect everything carefully. I’d probably test the power supply without it being connected to the motherboard. And in case the Y Safety Capacitors had failed (closed circuit, which they should not, but it is 40+ years old) I’d avoid touching any metal that should in theory be ground. If the X Safety Capacitors have failed close circuit, there is a risk of fire. If the Y Safety Capacitors have failed close circuit it is a risk of shock.

          1. The original IBM PC from early 80s did not include a realtime clock or configurable bios settings. They had DIP switches and you needed an add on board for a clock. If you didn’t have the add-on board, you’d have to set the clock every time you booted it up (from floppy).

          2. Concerning testing the power supply disconnected. Those early IBM PC power supplies were not designed for that type of operation. Service centers had dummy loads that were designed to be connected to the power supply for testing. I would not recommend testing the supply without some sort of load, or you might damage and otherwise workable power supply. I haven’t done any research but hopefully you can find suggestions for dummy load values.

  3. I don’t normally agree with the “not a hack” comments, but turning on a computer is not a hack. It is interesting news, perhaps it should have been in the Sunday news roundup.

  4. Wow. It’s interesting to see the Apple I, just a board, no case. It’s so cute and must have been so exciting at the time. Woz did such a great job engineering it. There was so much potential there. If history were re-wound and allowed to play forward again who knows what all it could have been, great or terrible. Who knew what it would become. It’s kind of like looking at a baby picture of Hitler.

    1. It’s more that Apple kept on going, while most early companies lasted a few years before dying off.

      The Apple I was not that significant. About 200 were sold, fifty of them going to the Byte Shop. So most attention in California. It was in a crowded field of companies with low runs. The Sphere 1, I wondered at the time if many sold, is said to have sold 1300 machines. The Sol 20, which was on the cover of Popular Electronics, apparently there were 12,000 units sold. But virtually nobody mentions the Sphere, and the Sol 20 has faded from view.

      But Apple kept going, so looking back, people give the Apple 1 more importance than it had at the time. It’s the same way Steve Jobs is given technical expertise, history that happened before most people noticed, so it’s colored by later history.

    2. Mr. Wozniak was one of us.. Tinkerer, hacker, ham..
      While I don’t know anything personal of him, I see that he built things to last, to be functional.

      The Apple company of the Apple II times was a different Apple from the Macintosh times. That’s one of the reasons why Mr. Wozniak left the company.

      Likewise Apple from the early-mid 90s was a bit different from the Apple we have now. In the 90s, Apple was some sort of “thought factory”. They dreamt about making great products, but were financially not successful.

      Also, they licensed System 7 to other companies, making the Macintosh platform equally open as the Windows platform. Very good for the users and software developers, bad for the financial situation of the company.

      But back to the Apple I and II. Apple IIs had an open design, used standard components. IBM adopted this with the PC 5150. The PC slots were derived from Apple II technology. Back in the late 70s to early 80s, the computer world held high opinions of Apple as “the good guy”.
      Especially the open design and expandability made the Apple II (including its numerous clones) a friendly ecosystem.

      These times, I’m afraid, were completely over from late 2000s onwards. That was the last time when Power Macs and Mac Pros were expandable, service-friendly.

  5. It is a really great news to know that this magnificient Apple I motherboard is still runnind despite its old age!

    But i’ve watched the videos, and i’m not really convinced by the way they did that test.

    From the beginning, i’m unsure that using ESD safe gloves without earth connection (to unbox and transport the board from museum area to lab) is of any use. Discharging oneself and use antistatic shoes (and clothes without any ESD risk) would have been more safe.

    They also say that they have used lab power supplies because it would have been too risky to use original power supply. But according to Apple I schematics here: https://www.applefritter.com/file/apple-1-schematics-3-3jpg
    the power supply is only a transformer, nothing else. All other power supply components are on the motherboard: bridge rectifiers, capacitors and regulators.

    It seems also that they used the J1 connector to input power supplies, so they did not bypassed any of the power supply components.

    But instead of inputing AC power supply from original tranformer that is normally supplying 10V and 28V (with center tap to earth so -14/+14V), they input already regulated DC power supply, so full wave bridge rectifiers and the 3 big blue capacitor normally used to regulate the AC power supply to almost DC are not really use, despite not completely bypassed.

    But i don’t think it would have prevent some problems in case of some diodes or capacitors were faulty, like possibly shorted.
    Using original 45 years old capacitor without testing ESR nor reforming them is probably not the best idea, and it would have been better to know if they were faulty before applying power supply, instead of waiting for any magic smoke or flame.

    That also means they used the original regulators to provide -12/-5/+5/+12 to the motherboard components, and they could have also been faulty.

    They were supposed to use current limited power supplies, which should have been probably a safe move in case of a short somewhere. But see below…

    I’m also unsure that turning them off/on with motherboard connected is a good idea.. Depending on the power supplies design, there’s a risk of a brief uncontrolled behaviour/power supply.

    And what is the relationship between the variable resistor used to adjest the composite video output level and all crazy characters displayed on the screen at the beginning? They say that adjusting this output level made the right characters displayed, but it should have only changed the output brightness and may be synchronization on the monitor. But it should not have any effect on the displayed characters.

    But they also changed the first output voltage from Constant Current mode (blue led) to Constant Voltage (red led) and the current went up from 1.04A to around 1.4A and so does the voltage from 7.6 up to 11V, meaning they were not providing enough current, so voltage was too low.

    And then later the second power supply was also cranked up from -17/+17 to -19/+19 (while motherboard still powered on).

    And i don’t think the PeakTech 6075 power supplies they have used has any current limit protection.

    So it seems that at first only the first power supply was using Constant Current (=current limitation) but not the second, and later on none of them. So finally there was no protection provided by the power supplies!

    And the Apple I user manual says that one should provide 8 to 10 VAC at 3A, and 28VAC Center tapped at 1A. So providing 11V DC and -19/+19 DC is quite higher.

    So all in all, despite what they say, i’m not sure they took all the required precautions for testing such a precious relic. Fortunately, it did not go bad!

    1. “They also say that they have used lab power supplies because it would have been too risky to use original power supply.”

      If that’s true, then these dudes did a big mistake indeed.

      Bridge rectifiers need AC to properly work!
      Feed them with DC, and half of the diodes are not working. That is bad. The working diodes are then overburdened.

      That’s the same stupidity that’s happening with the aftermarket PSUs for our European NES. They are no proper 9V AC transformets, but cheap switching PSUs with DC output.

      Anyway, perhaps that’s a generation thing also, not sure. My generation is simply too ignorant/arrogant to care about technology from the past. We’re using our overdeveloped technology, that we consider superior no matter what, without thinking about the actual needs. Oh, well. 😔

  6. On replacing capacitors, on a original machine this valuable, I would gut the capacitors and install a smaller (in size) modern capacitor. This is commonly done with antique radios of value. However, in this case with BOTH ends of the capacitor visible, this might take some real artistic/model-making skills as well as the electronics skills.

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