PDP 11 gear finally moved

Ummmm - his PDP-11/34 most certainly does use switching power regulators. ;) On 7/17/2015 4:06 PM, John Robertson wrote: > On 07/17/2015 11:53 AM, Mouse wrote: >>> I do find this witch-hunt against capacitors to be curious, given how >>> few I've found to have failed. I suspect a lot of it comes from >>> audiophools who think this is the way to fix anything... >> Perhaps. But not all of it, certainly. I'm currently four for four >> fixing dead flatscreens by re-capping their power supplies; I imagine >> others have similar experiences. It's not a huge stretch to imagine >> that other power supplies may have similar issues; even if it turns out >> to not be the case, there is probably at least a little "can't hurt >> anything, right?" running around. >> >> /~\ The ASCII Mouse >> \ / Ribbon Campaign >> X Against HTML mouse at rodents-montreal.org >> / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B >> > This is not surprising given the vintages of the machines. Modern > machines using switching power supplies (15kHz+) must have capacitors > with low ESR and high capacity to run properly. > > Older linear power supplies ran at 50/60hz and as such the capacitors > had much less ripple current (and low frequency to boot) to deal with > and the engineers typically over designed the values of capacitors to > allow for some degradation. The machines you are playing with cost > fortunes back in the day - they HAD to be reliable as possible. > > Modern caps run at or near their rated temperature (105C) last around > 1,000 to 5,000 hours. The old linear supplies rarely heated the caps > much over 40C and thus the caps would last decades...I put fans on our > LCD monitors in our games and they last just fine. > > No fan? Expect a year or two at most before failure. > > John :-#)# >