PDP 11 gear finally moved

Jay Jaeger cube1 at charter.net
Fri Jul 17 16:19:54 CDT 2015

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 :-#)#

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