I recently picked up a 2nd HP 6299A power supply. these are nice 0-100V .75A power supplied with adjustable current and voltage regulation. they also can be wired in master-slave series mode for tracking Bi-polar operation. perfect for designing amplifier stages! as these supplies are now 40+ years it is time for some maintenance and upgrades! All the electrolytic caps will have to be replaced. As capacitor technology has gotten better and smaller. I have an opportunity to upgrade the capacitors. But the questions is, where and by how much?
The owners/service manual can be found here.
http://cp.literature.agilent.com/litweb/pdf/06299-90001.pdf
Looking at the main bulk supply capacitors. They all appear to be pretty small. 3 main supplies, all half wave rectified. The main 150V supply has a 710uf cap, the 125V supply has a 200uf cap and the reference 27V supply which I would think is pretty critical, only has a 100uf cap! I would think all 3 of these supplies would benefit from a decent increase in uF!! Now as Overkill is my nature, my first thought is to stuff as much uF as I can in there. Putting overkill aside for a moment, How much of an increase would be of benefit?
And what about R49 (and R11)?? here we have a 2.2K 20 watt resistor across a 150Vdc line just idling away dissipating 10 watts of heat! and they stink! burning off 40 years of lab and attic dust and dirt! scrubbing them in alcohol helped but... why is it there? all I can think of is that it is to quickly drain C14 at shut off so there is no errata out of the supply after power off. To me it just seems a waste to be burning up 10 watts of heat for no reason. why not add a relay to the 120V line that would connect the resistor across the supply at shut down? what am I missing here??
The owners/service manual can be found here.
http://cp.literature.agilent.com/litweb/pdf/06299-90001.pdf
Looking at the main bulk supply capacitors. They all appear to be pretty small. 3 main supplies, all half wave rectified. The main 150V supply has a 710uf cap, the 125V supply has a 200uf cap and the reference 27V supply which I would think is pretty critical, only has a 100uf cap! I would think all 3 of these supplies would benefit from a decent increase in uF!! Now as Overkill is my nature, my first thought is to stuff as much uF as I can in there. Putting overkill aside for a moment, How much of an increase would be of benefit?
And what about R49 (and R11)?? here we have a 2.2K 20 watt resistor across a 150Vdc line just idling away dissipating 10 watts of heat! and they stink! burning off 40 years of lab and attic dust and dirt! scrubbing them in alcohol helped but... why is it there? all I can think of is that it is to quickly drain C14 at shut off so there is no errata out of the supply after power off. To me it just seems a waste to be burning up 10 watts of heat for no reason. why not add a relay to the 120V line that would connect the resistor across the supply at shut down? what am I missing here??
