Problem Overvoltage (7805) solved


Peter
 

Hello,
1 month ago i build a 20m QCX. After Power on immediately the FST died in smoke. I found out that there was a short at the 7805. The Strip lines are yery close for the 7805.
On Internet (www.qrpforum.de) I found a good article from DL3ARW which described the Problem with the 7805 if a short between the contacts send 12V to all IC's.
Here the link what he made to solve the Problem (in german) for the SI5351a.
https://www.qrpforum.de/index.php?attachment/20940-qcx-si5351-78l33-dl3arw-vers01-2-pdf/
He used a 78L33 (cost 0.49€) in place of the 2 diodes und an additional condensator. This save the SI 5351a from overvoltage. Also an additional Diode between in-and Output of the 7805 help in case of a short between in- and Output.

73 Peter (OE1OPW)



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Peter OE1OPW Vienna