Dentron Clipperton L and Yaesu FL-2100B have no grid current
metering, so B- is chassis ground.
I just did the hard grounding of grids on my FL-2100B. cathode
goes through bias diodes to ground with cutoff resistor switched
with an extra high speed 12V relay. Also changed the amp to +ve
12V keying and removed the ALC stuff. It works really well.
73, Alek VK6APK.
On 7/01/2025 11:27 am, Jim VE7RF via
groups.io wrote:
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On Sun, Jan 5, 2025 at 07:02 AM, John Sparkes wrote:
Hi fellas
Sounds like you guys learned in your hobby what
I used to teach my junior electrical engineers. Of course,
they all worried about the hot wire. I told them in order of
importance, it’s earth, then neutral, with the hot wire way
down the list. The green (E) and black one (B-) will kill
you or land you in prison (as the designer). Same applies to
amps !
John
You can either float the supply, OR grnd the B+.... OR grnd the
B-.? ? If you grnd the B+ to the chassis.... you now have a -5kv
supply...which will also kill u.? ?This assumes the safety
diodes are either not installed or have blown open ( normally
wired between B-? and chassis).??
You never grnd the B- to the chassis....... it's always floated
a bit.? ? Done that way so you can measure plate and grid
current.? ?In the old days, a 10 ohm resistor was wired between
B- and chassis.? Works BUT, if the anode arced to the grid in a
GG amp...or B+ arced to the chassis, the path for fault current
is up through the resistor, then back to the B- of the filter
caps...completing the loop...and of course the 10 ohm resistor
grenades.?
These days? RVS connected diodes are? used between B- and
chassis....then the B- is always within +/- .7 vdc from chassis
potential.??
?
