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33

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 most first-world nations), with thermal considerations factoring in somewhere further down the list. The latter tended to point towards implementing a switch-...


17

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 than the other components. My understanding is that it's called "CAN +5V" because it supplies the components in the shielded metal "can" on board. [1] Note that ...


13

How does the C64 get an accurate TOD clock on 50 Hz power? It doesn't, as the Kernal doesn't care for the build in TOD. The Kernal is a quick hack, taken straight from the VC20, operating the clock on interrupt base - like since PET times (as explained on another question about the 6526). If it would care, it could do so by simply handling Bit 7 of CRA (...


11

Aside from Cromatix great answer, the thing to consider was difference in power. Typical home microcomputers (like ZX Spectrum or Commodore 64 etc) used power supplies with about 10-30 watts, while IBM PC XT has chunky 130W power supply (which increased to 192W SMPS in IBM AT). That much power requires much more space, and would be quite unwieldy as separate ...


9

If you're really willing to do some jiggery-pokery, find some small gauge solid copper wire (like the twisted pairs from a CAT5 cable - I like to cannibalize old multi-conductor telecom cables) and get yourself two longish bits of wire. Strip the insulation back about 1 inch on one end of both wires. Now find a toothpick or something very close to the ...


7

I think you have a fake or mislabelled adapter. These symptoms seem to me to be those of a cheap adapter that's browning out when it's trying to supply the current the laptop wants at the voltage it wants, which is something that fake or mislabelled adapters would certainly do.


7

The external power input on an Apple IIc is a male 7-pin DIN jack. The standard Apple external PSU takes a country-specific input voltage (105 to 129 VAC, 60 Hz for North America) and provides (unregulated) 15 VDC. Though on page 11 of the Apple IIc Technical Reference Manual it says that the internal power supply "operates from a 12 to 15 VDC input ...


7

With only a 250W power supply you may be pushing the limit with two video cards, but it's hard to be sure. Neither of the video cards you're planning on using are particularly power hungry. I suspect nether comes with a fan, and the GeForce2 MX may not even have a heat sink. The PCI connector can only supply 25W and I believe the AGP 1.0 interface had the ...


6

The IBM PC wasn't a "home computer" -- it was intended to be a business computer, and needed to suit the needs of a business owner. Having the PS in the case eliminated extra connections (for the user) and made everything fit neatly on a desk. (And it should be pointed out that the PC was not IBM's first "personal computer". The IBM ...


5

I would say that it is more likely that the laptop was shelved because it's internal power circuit is at least partially shorted. This would explain the symptoms observed from the power supply LED. I, personally, have run into several laptops that had this problem. I would test the power supply under some sort of resistive load, such as a 12 Volt ...


5

The earliest personal computers of the 1970's, including the Altair 8800, had built in power supplies. The power supplies were often oversized to allow expansion boards to be added to the system. As the computers became smaller and more limited in expansion options (dare I say toy-like?) it became possible to power them with an external supply. It was ...


3

Another issue, outside the heat and multiple voltages issue, is the safety issue of low-voltage DC cabling. Home computers didn't draw much power, so a 5 – 12 V wall wart on a fairly short, thin two-conductor cable was considered safe enough. For example, the ZX Spectrum used a 9 V 0.7 – 1.4 A supply feeding a simple 7805 regulator, consuming ~650 mA at 5 V (...


3

Good points in earlier answers, but one is overlooked. The Ibm PC needs a set of different voltages, like +5V for the main board, +12V for disk drives, -5V for the RS-232 serial interface, -12V in case you have a special board that needs it. It would be quite impractical to have an external power supply connected with a cable to the PC with that many ...


1

That question is a bit broad. what parts of 'pickyness' are meant? One needs to distinguish between the CRT as main powered device and the signal path. Also, if CRT sould refer to 'just' CRT or TV sets. Also, it depends quite alot on the technology used, as CRTs came in countless technological variations. From 12V DC feed all the way to 400 Hz AC. As a ...


1

That's tricky. PC video cards had to be compatible with old CGA/MGA/EGA/VGA standards over ISA which didn't offer plug and play and remapping. Your two video cards may be incompatible, conflicting over accesses to registers, for example the palette or Video RAM in A0000.


1

Well, this does work, though it produces a quite noticable spark at the PSU output when I plug in the banana connector, even though the Apple's power switch is in the off position. (The Apple IIc still draws about 35 mA of current at 15 V even when it's powered off. When off, the +V power input is connected to a single pin on the PSU card connector via line ...


1

A history of failing is maybe a strong statement, but for what it's worth, I've seen a couple of failure modes of the power switch during C64 repairs. The most typical is that solder joints become loose due to the mechanical stress on the button, which can lead to no or poor connection, similar to what you describe. This can normally be fixed by resoldering ...


1

The "overheating" smell might emerge from the dust accreted on the heating components, if the device was off for a long time. So you could try to clean the dust off the PCB and components to get rid of the smell.


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