12 Jun
2009
12 Jun
'09
1:44 p.m.
----------------------------------------
Date: Thu, 11 Jun 2009 23:37:37 -0700
From: eric at brouhaha.com
To:
Subject: Re: Move on, nothing to see here (was RE: the arrogance of youth [was RE: UNIX
V7])
Ian King wrote:
Hi
The older ceramics are notorious for going short when used
in low current applications. As bypass caps they would self
remove the short because of the current. In low current
applications they just become vary leaky.
Having worked on pinball machines, I've replaced a lot
of these bad caps when used in the switch inputs.
I've also replaced a few when in the services on radio
equipment.
I'm told it is related to metal migration.
I have seen tantilum caps used for RC timing.
Dwight
_________________________________________________________________
Insert movie times and more without leaving Hotmail?.
http://windowslive.com/Tutorial/Hotmail/QuickAdd?ocid=TXT_TAGLM_WL_HM_Tutor…
we just got a restored PDP-8/TC08/TU56 booting
OS/8!
Cool!
After calibrating the TC08, I turned off the
system to put all the 'skins' back in place, fired it up... and it wouldn't
boot After checking the obvious things, I decided to let the system warm up for fifteen
minutes or so. Yep, it booted fine.
Something tells me I need to look at the RC components in those one-shots and clock
circuits, and probably replace some realllllllllly old capacitors. -- Ian
I can't imagine that they would have used electrolytic capacitors in
those, and I don't think ceramics are likely to have gone bad unless
they've been subject to extreme mechanical shock. I'm not sure about
other kinds of capacitors, but I'd expect they'd most likely have used
ceramic.
I certainly wouldn't go replacing ceramic capacitors without using some
freeze spray to confirm that it is a temperature problem and identify
the failing component.
Eric