11/45, sick or not?
mcesari at comcast.net
Tue Jul 5 22:31:11 CDT 2005
On Jul 5, 2005, at 6:45 PM, Jay West wrote:
> Joe wrote...
>> Are you sure that the lights aren't blinking too fast to see?
>> Perhaps you
>> can hang a logic probe (with a pulse extender) on one of the
>> lights to be
> I'll try that tomorrow... but I wouldn't think that is what is
> happening. Also, pardon my lack of knowledge, but... shouldn't I be
> seeing the .2v ripple as an AC component (ie. a sine wave)? It's a
> very clear perfect sawtooth. And it's exactly the same on all the
> 5V regulators, which strikes me as odd.
The sawtooth is correct for h744's. 0.2v is a bit much, but shouldn't
be a show-stopper. The 11/70 maint. manual has a
decent description of the h744 on pages 4-59 thru 4-62 (EK-11070-
MM-002_May79.pdf on bitsavers). It says the voltage should
range from 4.95v - 5.05v. (The description in the 11/45 manual isn't
Also check for high frequency spikes at the valleys of the sawtooth,
5v_ /\ /\ ... If these are more than 2 volts (go below
3v), you will have "issues".
/ \/ \/ Welcome to the wonderful world of aged DEC
switching supplies =:O
3v_ | |
Ascii art, feh. Put up some pics of the `scope display. :-)
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