On Fri, 17 Aug 2007 13:21:42 -0400 "Michael A. Terrell"
wrote in Message id:
:

JW wrote:

Hello all,

I have this HP 8116A 50MHz Programmable pulse/function generator that's
almost working perfectly. However, whenever the amplitude is set below
EXACTLY 10.00 volts, the output puts out nothing. 9.99 volts and lower
does not work at all. Any ideas?

Thanks!


Do you have the manual?

http://www.home.agilent.com/agilent/redirector.jspx?action=ref&cname=AGILENT_EDITORIAL &ckey=615544&lc=eng&cc=US&nfr=-536900193.536900597

Yup. Got it, but no schematics on that one...

Some of the programmable generators use relays to switch pads in and
out, to set the output level. They fail, from heavy usage. I had most
of them go bad in an old HP 3325B over a couple year period of daily
use.

Thanks! That gave me the clue I needed. I found a number of reed relays
and 'scoping out their coil inputs while switching between 9.99 and 10.00
volts noticed that one of them was only getting down to about 2 volts.
Traced it back to a 74LS374 octal latch - it's pin 9 output was bad. The
chip is located on the bottom board of the 3 stacked boards in the unit.
The chip is located on the right side near the front panel when the unit
is oriented facing you.

Thanks again, Michael. And thanks to N Cook and Chris as well!