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QRP Plus with blown C41 on Transmitter board

John #93 Hi folks,? I'm trying to help out a friend with his QRP Plus rig.? Power was applied in reverse polarity and it blew C41 on the XMTR board.? It looks like a tantalum cap but it was mostly destroyed so there is no way to determine the value from looking at it. I have the XMR PCB board layout and the schematic.? The layout shows C41 just behind C39.? However, on Figure 18 of the schematic, there is no mention of C41 at all.? Instead, it shows two C39's flanking D7.? One is a 220uF electrolytic which I see on that board.? The other C39 shown on the schematic lists it as 10NF.? I'm pretty sure that should be labeled as C41 on the schematic.? Assuming I am correct, I also question the value listed on the schematic, as 10NF (nano farads), or .01MF or 10k PF, etc. Can anyone help with a value of C41? Thanks in advance, John? ? ?? ?
Larry East All Messages By This Member #94 开云体育 Didn't you get my reply? Hi John, Is the damaged cap an electrolytic?? If so, it's value probably is (was. . .) 10MF.? At pointed out in first of my articles, the 1N4005 "reverse protection diode" is essentially worthless since under revered polarity it will probably blow (open up) before the fuse blows resulting in a number of things being blown in the rig.? So -- I am afraid that you have more to deal will than just a beheaded cap -- like the output IRF510 (and who knows what else).? All I can say is "good luck" . . . 72/73, Larry - W1HUE On 11/3/2021 2:01 PM, John via groups.io wrote: I'm trying to help out a friend with his QRP Plus rig.? Power was applied in reverse polarity and it blew C41 on the XMTR board.? It looks like a tantalum cap but it was mostly destroyed so there is no way to determine the value from looking at it.
John #95 Hi Larry, I didn't see your reply and checked my spam folder too, but I appreciate you replying here. The damaged cap looks like any other tantalum I have ever seen.? The owner claims that he operated the radio after this happened and no other issues were noticed. I think based on what I have observed + your input here, I will offer to replace the blown cap with a 10MF tantalum with no guarantees and see where it goes, or he can send it off to another guy he's dealt with in the past.?? I guess whoever was building these radios in the past had some kind of a backplane that they could use to work on these things without having to dismantle the stack.? And yes, I did read your article. Thank you again for responding.?? John - N4WFK? ? On Wednesday, November 3, 2021, 07:18:55 PM EDT, Larry East <w1hue@...> wrote: Didn't you get my reply? Hi John, Is the damaged cap an electrolytic?? If so, it's value probably is (was. . .) 10MF.? At pointed out in first of my articles, the 1N4005 "reverse protection diode" is essentially worthless since under revered polarity it will probably blow (open up) before the fuse blows resulting in a number of things being blown in the rig.? So -- I am afraid that you have more to deal will than just a beheaded cap -- like the output IRF510 (and who knows what else).? All I can say is "good luck" . . . 72/73, Larry - W1HUE On 11/3/2021 2:01 PM, John via groups.io wrote: I'm trying to help out a friend with his QRP Plus rig.? Power was applied in reverse polarity and it blew C41 on the XMTR board.? It looks like a tantalum cap but it was mostly destroyed so there is no way to determine the value from looking at it.

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