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Hello,

Last time I used my uBitx the magic smoke was released. The radio was idling, just listening to something (probably FT8) when I noticed a glow in the room and pulled the plug. It looks like I may have just burnt the trace nearest the edge on the underside, which I think is the main power rail to the switch/pot. I repaired this today and the unit powers on, but I won't test it properly until it is back in the case with everything connected properly.

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On here there is mention of connecting separate fuses for the main board and the finals, using the P1 header. My brain gets confused by schematics which have breakouts, so I do not understand how P1 is connected: the article suggests that 3 connects to ground (correct) and that 1 and 2 connect to the main board power rail and the finals rail (not sure which is which). My DVM probing is showing the schematic's suggestion that 1 and 2 are connected rather than being separate.

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So, my question to anyone who has performed this addition, or is better understanding of the schematic, is whether I should disconnect the center pin of the barrel connector and connect two wires running to the two fuses, then respectively connected to pins 1 and 2 on P1, or whether I should be tapping a trace elsewhere for the finals, or just run two fuses in series (!?). Or just a single 3A (or 5A) fuse.

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When I had my magic smoke episode I did have a 5A fuse, but it may have been one of questionable origin in the power distribution block. I have subsequently replaced all my fuses with Littlefuse things, since they do seem to burn when they should.

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Thank you,

KK7BCO

KK7BCO,

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The article you are using is for the v5 and earlier uBITX. ?The P1 connector did provide separate feeds to the PA and the rest of the radio. ?On the v6, The two pins are connected together under the plug. ?You could remove the connector, cut the trace, and then reinstall the connector.

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It is not worth doing just to provide separate fusing. ?If you want to get a little more power out, you can provide separate power to the PA, maybe 20 volts. ?That requires two power supplies or one higher voltage and a buck converter to drop to 12 volts for the rest of the radio.

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3 amps is the correct fuse for the radio when operating on 13.8 volts. ?The maximum current that I have measured is 2.5 amps.

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73

Evan

AC9TU

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Evan, thank you for confirming what I was seeing.

I don't plan on over-driving the finals, they worked well before and would give around 11w peak, which is plenty.

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More soon,

Tobias