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100 votes

Was there ever any reason to wait 30 seconds to restart a c.1995 PC?

I am an EE system designer. I have designed many PC systems (and non PC ones). I do lots of power supply work and have dealt with many HDDs. As always, there is bound to be an exception somewhere. ...
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63 votes
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Why did Commodore fill their power supplies with epoxy?

Epoxy offers two advantages -- it is an electrical insulator, and it conducts heat better than air. Transformers and inductors are generally potted with epoxy for this reason. [ref] Perhaps the cause ...
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  • 8,166
62 votes

Why did computers use a power supply with a socket?

The socket (or rather inlet) is most definitely standard, it’s a IEC 60320 C14 inlet. The standard was published in 1970. C6 and C8 are commonly used for laptop power supplies and smaller audio ...
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55 votes

Was there ever any reason to wait 30 seconds to restart a c.1995 PC?

The reset button does not affect the power supply at all. It sends a reset signal to the CPU (and probably the bus). Some power supply designs indeed will wear quicker if quickly switched on and off, ...
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47 votes
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Why does the Cray 2 use 400 Hz power, and why generate that from motors?

The reason for any higher frequency supply is almost always the same: you get to convert a single input to different voltages for less wasted heat in a smaller volume. Such systems were very common in ...
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43 votes

When/why did computers come to have push-button main power switches where on and off is the same push action?

AT power supplies often did have a line-voltage flip switch. Indeed many later machines also have such a switch around the back to totally switch off the system. However ATX and later systems use a &...
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  • 711
39 votes
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When/why did computers come to have push-button main power switches where on and off is the same push action?

TL;DR: So: why use push power buttons? The same reason that it is used in other appliances: it's convenient. The Works: Just think, early (IBMish) PC had their power switches at the right side all ...
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  • 173k
36 votes

Why do Game Boy Colors not want nickel-cadmium batteries?

I suspect more "don't disappoint the users" than "harm to the device". From the Wikipedia AA article, not only is the nominal voltage lower (1.2V vs. 1.5V for both alkaline and ...
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35 votes
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Why did the IBM PC have an internal power supply?

Internal power supplies, while not universal, were not unusual at the time. The major considerations were cost, ease of design, and safety (that is, passing safety regulations that already existed in ...
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34 votes
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What is the Commodore 64C "France version" and why does it need a beefy resistor?

As noted in the question, the resistor is there to allow something to consume more current without voltage dropping too much. But what consumes more current may not visible in the schematics. France (...
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  • 17.9k
31 votes
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Can a Japanese (or US) PSU for Nintendo 64 be run with 230 V mains?

The supply shown in the video will most likely blow up if you connect it to 230V mains. At 1:08 in the video you see the printing "200V" on the main filter cap. There is no plausible way to ...
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29 votes

How and why did the ZX Spectrum use so many voltages?

I will start with the last question: The power adapter is a very cheap one. In fact, the voltage without load can raise up to 15-16V. 9V is the nominal supply voltage under the normal load that the ...
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26 votes

Why does the Cray 2 use 400 Hz power, and why generate that from motors?

I'm not sure that in 1986, the state of the art used 400 Hz as a frequency for timing the signals and the circuits. The 400 Hz is not related to any kind of timing. It's about getting size and losses ...
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  • 173k
23 votes
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Why the switch to "Mickey Mouse" (type C14) power cables?

It's because the C14 connector is rated for higher current (10A, up to 2400W), which means that it must be attached to a thicker and thus more expensive and less flexible cable. The cable can't be ...
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22 votes

How can I power a C64?

Do not use an original Commodore 64 power supply, especially if it has not been tested. They're prone to fail, and when they do, they'll take the C64 with it. But if you do intend on using one of ...
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22 votes
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How can I power a C64?

The Commodore 64 requires a power supply that provides both 9V AC and 5V DC. If you're interested in building your own, the power supply has a male circular 7 pin DIN connector. Pins 1-3 are ground (...
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  • 8,413
22 votes

Why did Commodore fill their power supplies with epoxy?

Electricians some times (or used to) do similar techniques when configuring wiring -- once the wires were in place, they would fill the cavity with a non-conductive resin or epoxy, so that the chance ...
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  • 321
22 votes

Was there ever any reason to wait 30 seconds to restart a c.1995 PC?

My best guess is that it was (and is) all about getting the computer into a well-defined state. To make the CPU start at the correct address, it needs to get a RESET signal or something equivalent. ...
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22 votes

Why do Game Boy Colors not want nickel-cadmium batteries?

Two simple reasons. Different battery chemistries have different voltage and safety. Standard alkaline batteries are nominally rated for 1.5V, but they can have more than 1.6V when brand new and are ...
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  • 17.9k
20 votes
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Does switching on an old games console without a cartridge damage it?

In general, no. Cartridges from the first few generations were really only breakouts for ROM chips and thus were mostly a collection of address and data lines with a +5V and GND at minimum and perhaps ...
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  • 14.3k
18 votes
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Why did the C64 use a separate "CAN" +5 V power supply for some chips?

This is done to stop HF noise from spreading through the VCC rail. The VIC and the 8701 clock generator (U31) run at much higher speeds than the rest of the C-64, and thereby generate more HF noise ...
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  • 7,854
17 votes
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Powering up my ZX Spectrum

World Of Spectrum says: Input: 240V AC, 50Hz Output: 9V DC, 1.4A Centre Polarity: -ve (inner diameter is 2.5mm)
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  • 2,307
16 votes

Was there ever any reason to wait 30 seconds to restart a c.1995 PC?

All the other answers talk about delaying switching back on to prevent possible damage/wear of the power-supply (which I fully agree with). The other reason for a delay that was "common knowledge" ...
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  • 1,006
16 votes

How does the C64 get an accurate TOD clock on both 60 Hz and 50 Hz power?

How does the C64 get an accurate TOD clock on 50 Hz power? It doesn't, as the Kernal doesn't care about the built-in TOD. The Kernal is a quick hack, taken straight from the VC20, operating the clock ...
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  • 173k
15 votes
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How can a computer use the drive's momentum for emergency power?

Any real attempt to use the momentum of the spinning disk to generate power would cause the disk to come to a halt very quickly. In essence, this is the principle behing regenerative braking of ...
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  • 7,609
15 votes

Why did computers use a power supply with a socket?

(This is about motivation (the why) of defining and adding a standard socket to devices and ment as an addition to Stephen Kitt's great explanation of the technical side - at some point a merge might ...
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  • 173k
15 votes
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Weird power lines for S-100, why no 5V?

Remember, we're talking about mid 1970s, that's before switching power supplies became common. The Apple II was an exception at that time. And it was almost half a century before tiny sized, dirt ...
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  • 173k
14 votes

Original Mac capacitor inspection

You can find a list of capacitors and other analog board components here: https://docs.google.com/spreadsheets/d/132RwzC8HM5ask-BdY_31txErOCwJDSkz099GY2XLpE0/edit?hl=en&hl=en#gid=0 This list is ...
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13 votes

How can I power a C64?

In Poland there was the Commodore & Amiga magazine in 1992-1995. In it's 7th number (July '92, pages 22-23) there was an article on how to build your own power supply for C64 written by Jerzy ...
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  • 618
13 votes

Can polarity inversion damage a ZX Spectrum?

You have damaged your Spectrum for sure. The first casualty is the 7805 regulator. These normally explode and release a "black smoke of the death" clearly visible, but yours doesn't seem to be the ...
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