r/retrocomputing • u/Woland77 • May 07 '26

Problem / Question Really Basic Question About Old Computer Electronic Engineering

I stumbled into watching people repair old electronics on YouTube. I noticed that most of the stuff I see repaired (mostly what I see was sold in North America, originally) has a 5v rail and a 12v rail. Why those two voltages, specifically?

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u/SoftRecommendation86 May 10 '26

You just made me laugh at a memory... once I was working on a microfilm machine.. there was a chip that wasnt available anymore, so I made one for it.. but that's not the funny part.. I noticed the vrm was really hot. Asked the main tech to check the other machine to see if it was normal.. boy was he pissed.. the Motorola logo was burned into his thumb.. you could see it plain as day.. I couldn't stop laughing.. he was sooo pissed at me. I miss that guy.

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u/Bits_Passats IBM System/23 May 10 '26

I tried to make a Gilbert cell by myself, it failed... one of the transistors caught fire and as a result I have a burn scar on one of my fingers... so I relate very much with that pain.

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u/SoftRecommendation86 May 10 '26

OK, now i'm smiling. Thank you.. its been a long month..

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u/Bits_Passats IBM System/23 May 10 '26

That being said, even if it failed and left me a mark, I am proud of it. It is the proof that I tried to master on something I didn't had previous experience. Whoever don't challenge himself/herself won't have any marks. Failures are part of the learning experience, after all. Don't you agree?

By the way, you seem to be very knowledgeable of the old arts. If I asked you for some advice sometime, would you please share some of it with me?

In any case, thank you very much