IMSAI Score update/Spare BYTEs/Got an Altair too
cctalk at randy482.com
Mon Jun 6 14:52:14 CDT 2005
From: "Dwight K. Elvey" <dwight.elvey at amd.com>
Sent: Monday, June 06, 2005 2:09 PM
> >From: ard at p850ug1.demon.co.uk
>>> By the way, the power supply, so far, has tested fine. I'm going to look
>>> for any ripple with the scope later today. I've never done that test --
>>> should I DC or AC couple the scope for that test?
>>AC coupled. That's really what AC coupling is for -- you want to ignore
>>the steady DC level (of several volts) and look at the (hopefully) much
>>smaller AC ripple on top of it. To do that you need to turn up the Y
>>sensitivity on your 'scope, and unless you have a differential comparator
>>input or something, you won't be able to keep the trace on-screen with DC
>>Don't worry too much about ripple on an S100 supply. The S100 supply is
>>not regulated -- the regulators are on each of the boards (the 8V input
>>is designed to be regulated down to 5V, etc). The regulators should take
>>care of small amounts of ripple on the backplane supply lines.
> For this particular test, using DC coupled is probably
> best. As Dave mentions, you just don't want the voltage
> on the unregulated 8 volt line to drop below 7 volts.
> It can tolerate a relatively large ripple.
In this particular case I would disagree. The Imsai is fairly well filtered
and I would expect less ripple, if there is much ripple I would suspect bad
caps or poor connections of the caps.
Of course when these caps fail you usually know it all the way down the
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