when I say that the IMSAI 8080 PSU has "soda can sized caps", I'm not joking

[gloriouscow@oldbytes.space]

@lynn holy shit. i bet that could make your elbow tingle

[regehr@mastodon.social]

@gsuberland @lynn the photo with the soda can made me clench a little

[gsuberland@chaos.social]

@regehr @lynn full of electrolytes

[realgene@hachyderm.io]

@gsuberland @lynn
Look at the size of the transformer, yup.
60 Hz are BIG waves...

[unlambda@hachyderm.io]

@gsuberland @lynn Looks like it's rawdogging the diode bridge: https://www.retrocmp.de/imsai/imsai_p05_psu.htm

[regehr@mastodon.social]

@gsuberland @lynn

[lynn@woof.tech]

@gsuberland you get unregulated +/-8V and +/-16 rails you’re supposed to do the regulation on each s100 card separately depending on your needs

[lynn@woof.tech]

@gsuberland

(more from page 87 if you're interested in further details https://dn790007.ca.archive.org/0/items/imsai-user-manual/IMSAI_User_Manual.pdf)

[lynn@woof.tech]

@xconde “just” 0.095 farad

[furrybeta@shark.community]

@lynn Wouldn’t want grab ahold of those leads when charged

[brouhaha@mastodon.social]

@lynn
And when they turn the power on, it's sure to dim the lamps
With plus or minus sixteen volts and fourteen hundred amps
– Frank Hayes, "S-100 Bus"

[nilsding@pounced-on.me]

@lynn the forbidden energy drink

[halcy@icosahedron.website]

@lynn feels like these could double as a smoke machine in a jiffy

[ronflaix@mastodon.gamedev.place]

@lynn I want to sip the power juice

[mia@tearoom.tearmoon.com]

@lynn @halcy I once disassembled an unsalvageable Thing that I don’t even remember the purpose of and it had like ten 500 μF / 250 V capacitors the size of a small boulder (think 500 ml cycling water bottle) each

…that were still rather charged.

[fae@pony.social]

@brouhaha @lynn i always wondered what that line was referring to... but last time i went digging i never found an answer... i guess now i know

[brouhaha@mastodon.social]

@fae @lynn
The S-100 bus power supplies were nominally +8V, +16V, and -16V, filtered but unregulated. Each card was expected to have linear voltage regulators from +8V to +5V, and, if needed, ±16V to ±12V.
The more cards in your system, the more amps of each supply you needed, though the "1400 amps" in the song is gross exaggeration.
Early Altair 8800 systems, and some others, had small backplanes with few slots, and were provided with wimpy power supplies.
1/

[brouhaha@mastodon.social]

@fae @lynn
The most common configuration IMSAI 8080 provided 22 slots and a beefy power supply, which resulted in MITS and other S-100 vendors having to offer similar configurations.
If you really did fill up a 22-slot backplane (e.g., with CPU, a few I/O cards, and sixteen 4K RAM.cards), you really needed a lot of amps. I'm sure that large S-100 system configurations were the inspiration for the song.
2/

[brouhaha@mastodon.social]

@fae @lynn
While almost everyone is aware of the dangers of AC line voltage, it is uncommon for people to be aware of the potential danger of low voltages. Skin contact with the +/-16V DC in an S-100 system is incredibly unlikely to cause any harm. You can grab the +16 with one hand, and -16 with the other, and your skin has high enough resistance that nothing happens.
3/

[brouhaha@mastodon.social]

@fae @lynn
But if you are wearing a metal watch, ring, etc, and get one of the supply rails shorted through it to ground or another supply rail, the supply will give all of the amps it can (usually much beyond its rated output, at least for seconds) through that metal. It can't electrocute you, but the metal can heat up enough to cause a serious burn. With a ring, potentially serious enough to lose the finger.
Lesson: remove watch and hand jewelry while working inside computers. Even PCs.
4/