Raj has seen several boards with R141 blown: ?/g/BITX20/message/32096
That resistor and the mmbt3904 at Q13 have quiescent currents that exceed their dissipation ratings.?
Q13 is connected to the antenna, can also blow if a nearby QRO transmitter causes Q13's Vbe to get excessive.
Transmit LPF caps will see around 100v pk-to-pk of RF (centered on ground) when driving 20 watts into 50 ohms,
at high SWR they will see considerably worse.
?
But many in the forum are successfully running with 24v into the IRF510.
I suspect most reports of damage are due to heat in the IRF510.?
That's how you learn. ?Good thing the IRF510's are so cheap.
Jerry
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On Mon, Oct 9, 2017 at 05:53 pm, Brent Seres wrote:
Jerry had some comments and concerns with several of the stock bitx components being stressed at voltages over 12 volts. I'm currently using a supply running about 13.5 volts. Has anyone had any problems with things failing when using a similar supply or fully charged lead acid batteries? I know the PA is fine, just wondering about the rest of the board.
