Allison,
Farhan discovered this spike on his sBitx. The wave goes down and
rises rapidly
and very high before settling down quickly. Enough to blow the
finals.
Disconnect C14 and see if that cures it.. the charging and
discharging during RX/TX
changeover is? an issue.
My first sBitx #9 was connected to the 20A shack PS after I
smoked something in RX.
Due to some unfortunate accident and vertigo could not fix it.
The next one #163 I connected to 2.5A PS just to be safe !!
This one sometimes starts and everything displays fine except it
doesnt show
any signals and a reboot cures everything, I can live with that
but a delay in
start may fix it.
73, Raj vu2zap
On 30/09/2022 6:08 PM, ajparent1/kb1gmx
wrote:
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Raj,
I suspect its has to do with the startup state of the Rpi and the
peripherals
it talks to.? By nature its undefined in many cases.
If I arrange power to the Rpi and front panel separate from main
board
I do not see the current spike on startup (powering the main
board).
So it appears something wants to start in an undefined state at
power up and causes a current spike.? Its likely the IO that
drives Q10
(TX enable power).
Next thing I'll try is disable TX command line to the main board
and see
if it starts up without current pulse.
Systems I've done in the past have a generated signal called
Delayed-power-good that is used to inhibit anything that can
do unacceptable actions until the MPU or whatever is stable
and takes command.? Its usually a very trivial circuit like a RC
and? gate as a schmitt trigger with a time less than 1 second.
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
Raj vu2zap