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I have an old computer, an ABC80 from the late seventies or early eighties, in which I have reason to believe one or more of the voltage regulators are broken.

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Now I wonder, what may be suitable replacement parts? I know that similarly named parts are still produced, but I am not sure about the details.

What about this for a 7805 replacement?

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  • \$\begingroup\$ What sort of computer is it? \$\endgroup\$
    – user1307
    Commented Nov 8, 2010 at 12:44
  • \$\begingroup\$ @tronixstuff, an ABC 80. \$\endgroup\$ Commented Nov 8, 2010 at 12:47
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    \$\begingroup\$ Ah - en.wikipedia.org/wiki/ABC_80. Nice one, have fun! \$\endgroup\$
    – user1307
    Commented Nov 9, 2010 at 3:31

2 Answers 2

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You can replace them with any equivalent regulator, so long as it is better in terms of current rating and in the same package.

For example, don't replace a 79M12 with a 79L12, because the M indicates a MEDIUM current level and is about 500mA-1A, while the L indicates a LOW current level which is usually ~100mA.

You could replace the 7805 with 7805 in a TO-220 package. The 79M12 could be replaced by any 7912 rated for ~1A.

Back in the day when that computer was produced, it was more expensive to produce a regulator which could do 1A vs. one which could do 500mA. It's still the same, but as manufacturing methods have improved, the price gap has shrunk.

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  • \$\begingroup\$ :) (Is it working?) \$\endgroup\$
    – Thomas O
    Commented Nov 8, 2010 at 13:43
  • \$\begingroup\$ @Thomas O, no, I need to order them first. Looking at where I could do that. Sweden has ELFA, which has EVERYTHING but they charge a lot for freight. \$\endgroup\$ Commented Nov 8, 2010 at 13:48
  • \$\begingroup\$ Ordered some regulators now. \$\endgroup\$ Commented Nov 8, 2010 at 14:21
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    \$\begingroup\$ @Amigable Clark Kant, your fault if the "fuses" need to blow. The older regulators have thermal protection, too. \$\endgroup\$
    – Thomas O
    Commented Feb 4, 2011 at 10:14
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    \$\begingroup\$ @Amigable Clark Kant Just warning you of the possible consequences, a fried PCB that is, or worst a fire, if you replace fuses with non-fuses. \$\endgroup\$
    – Thomas O
    Commented Feb 4, 2011 at 12:26
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Please be aware, on the 79xx regulator, the center pin (2) is common to the heat sink. The 79Mxx is isolated tab. If you ignore this you can get bad problems. Use the insulator, and screw bushing...

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    \$\begingroup\$ This is useful information, but it doesn't answer the question asked (and is about nine years too late to be of use to the original asker, as well). \$\endgroup\$
    – Hearth
    Commented Oct 1, 2019 at 14:27
  • \$\begingroup\$ Explaining the specific challenge in using a more generic 79xx seems like an answer, especially when a question literally asking for a part suggestion would under today's rules be closed as off topic. It's also likely that this is an "XY problem" since there's no real reason for confidence that the voltage regulators actually are bad, or if they are, that simply replacing them and not also fixing whatever caused their failure would be enough. Suspecting electrolytic capacitors, corrosion, or degraded EPROM contents would be more likely. \$\endgroup\$ Commented Oct 1, 2019 at 14:31

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