Oh, sorry, didn't realize they used switchers for the PDP-11s.
However I was talking with a friend of mine last night about my error,
and he told me that the switching supplies for the PDP-11s were very
unreliable back in the day. He often had to troubleshoot the machines
back then. A common failure was caused by static electric shock to the
machine would blow the supply. NO carpets allowed!!
John :-#)#
On 07/17/2015 2:19 PM, Jay Jaeger wrote:
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
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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 :-#)#
