Protection resistors need to be added to the drain of Q101 ?(suggest 150 to 200 ohms) & to the two diode¡¯s going to the TR circuit from +12. ? (suggest 470 ohms) In both cases, momentary high currents destroy semiconductors because there were no current limiting resistors. ?In the case of the Q101 switch it is almost a guaranteed eventuality,in the case of The two diodes, I don¡¯t know how it happened but any boo-boo with a test probe could cause it
There may be other portions of the circuit that need to be made a bit more hardened. Those are just the two that I have blundered ?into so far! ?
I have been impressed with the quality of the low pass filtering, but not so much with the vulnerability of specific parts of circuits. ? Since ham radio operators are usually given the right to repair their own equipment, providing some level of idiot proofing is a good idea. ? ? For example apparently there is now a diode across the power supply input leads. ? And a fuse was in the power cable that came with the used unit that I bought. ?
Fixing these vulnerabilities will in the long run reduce the complaints that the manufacturer eventually has to deal with. Not everybody is brilliant and we can all make mistakes! ?Been there, done that ??
Gordon Kx4z?
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On Jan 2, 2024, at 17:08, Evan Hand <elhandjr@...> wrote:
?H Steve,
The PA stages are the only real difference.? One addition to the production units (at least the one sent to me) I have not seen on any schematic is the TVS gate protection that is very much needed on the V2 circuit with the IRFZ24N finals.? Gordon Gibby has had issues with his V2 around the HV doubler and the T/R switching circuit around Q9 and Q101.? I implemented a different solution to the T/R switch and plan to add the series resistor to protect the voltage-doubling circuit diodes.
The IRF510 circuit seems to be more stable, so unless I see a lot of issues with it here in the group, I do not plan on implementing the mods.
As I stated in response to a request from Jens, I am happy with the hardware.? The software still needs work.
/g/BITX20/message/10738573
Evan
AC9TU
