i love the hp 6525A that we have at work
it's such a... Thing
weird box with dials on it on the bench with a couple wires sticking out
ridiculously heavy
makes a continuous ticking noise when plugged in (if the dials are set to anything other than 0000)
still works perfectly (if a bit out of calibration) when it's about 60 years old
they don't make things like that anymore
-F
it's a high voltage power supply, 4 kV/50 mA (max of 2 kV from ground, but the output is floating so you can do ±2 kV for a total of 4), and it's from an era where they advertised it being fully solid-state as a big selling point
and honestly that is a big selling point now, too; getting old equipment that uses tubes is always a pain because sometimes the tubes need replacing and sometimes they're ones that you can't get anymore
would love to have the schematics for it
-F
maybe we'll try to reverse engineer it sometime
it's not that complicated a thing; the dials on the front are just decade switches for resistances (and the 1s digit is a potentiometer for fine adjustment), that'll obviously just be a divider in the feedback network (probably a kelvin-varley divider?)
the converter itself is an enormous flyback--i do mean enormous, the flyback transformer is about the size of a box of tissues--running in a variable frequency mode
-F
that flyback transformer is the source of the ticking i mentioned earlier, by the way. under no load it operates at about 1~4 Hz depending on the set voltage, making a tick every time it switches, and as the load increases it ticks more, up to a maximum of something around 3~4 kHz (by our ear, anyway--we don't have perfect pitch so this is a very rough estimate)
it's quite something to look inside
-F
actually, would anyone happen to be good at digging up old manuals? i feel like this one would be a fascinating one to go through but our attempts have so far been stymied by the fact that modern HP has reused the number for a printer
-F
i wonder if we could just ask Keysight (the modern company that is what remains of HP's test equipment department)
they might not still have it, but they also might
-F
electronics test equipment from before around the 60s or 70s is always so much more reliable than modern stuff
-F