My unit has many connections between chassis and circuit grounds, most
of which look intentional. There are connections at the 1 MHz and 100
KHz BNC outputs (the 5 MHz output is transformer coupled). There's also
a connection at an SMC connector from the multiplier to the SRD final
amplifier. And a connection between the lamp oscillator ground and the
shell of the physics package. There's a suspicious connection in the
physics package that I'm checking out. It connects the ground for the
photocell preamp to the ground for the SRD. Seems rather odd.
Ed
On 4/29/2012 10:12 PM, Don Latham wrote:
A first-class engineered unit will have a single point where the chassis
and circuit grounds tie together, Sometimes it's a panel, where the i/o
connectors are coaxial. I've fixed units with good engineering and
sloppy construction where accidental extra common points have caused
problems.
The bottom pin (pin B) is connected to circuit ground which is connected
to chassis ground on my unit and the schematic confirms it. That could
be why you have to ground that pin to make your unit work. There
appears to be a broken or missing ground somewhere in your unit.
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