6 Jul
2005
6 Jul
'05
4:31 a.m.
On Jul 5, 2005, at 6:45 PM, Jay West wrote:
Joe wrote...
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
as good.)
Also check for high frequency spikes at the valleys of the sawtooth,
for example:
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. :-)
Mike
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
sure.
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.
Jay