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TDA2822 Smoke and FT8 Duty Cycle?
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I managed to let the smoke out of my TDA2822 this morning.? I built cables yesterday to connect the uBitx to my YCCC SO2R box so I could use my common headset and paddle / Winkey, and all was well with SSB and CW.? This morning I hooked up a USB sound dongle to the mic and phone jacks and made three FT8 QSO's before I noticed some nice wisps of grey smoke escaping from the uBitx case.??
I assumed it was the IRF510's from the FT8 duty cycle, but on opening the case I saw that the TDA2822 was cracked.? I read up on uBitx.net and saw that one of the causes of this failure is a mono phone plug in the stereo phone jack.? Sure enough, the phone plug I was using was mono.? It blew the AC power fuse as well (3A fast blow that comes with the Amateur Radio Kits of IN case).?? It's not the WX version of the TDA2822, so I believe it's my fault, not a faulty part. I ordered a couple of NJM2073D's from Mouser (uBitx.net pointed out they are a pin compatible TDA2822 equivalent), and some IRF510's just in case. Hopefully there's no hidden damage.? Which brings me to two questions: 1)? Assuming the problem was the mono plug shorting out the two outputs of TDA2822, is it likely that there was any other damage? 2)? This is a stock uBitx with stock heatsinks.? Can I run FT8 with its 50% duty cycle (worst case 15 sec TX / 15 sec RX) at full power??? 73, Rowland K4XD |
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I put about a 5 ohm resistor in the wire coming from the ubitx going to the speaker jack just to try and eliminate that type of problem. On Fri, May 18, 2018 at 4:41 PM, RowlandA <rarcher@...> wrote: I managed to let the smoke out of my TDA2822 this morning.? I built cables yesterday to connect the uBitx to my YCCC SO2R box so I could use my common headset and paddle / Winkey, and all was well with SSB and CW.? This morning I hooked up a USB sound dongle to the mic and phone jacks and made three FT8 QSO's before I noticed some nice wisps of grey smoke escaping from the uBitx case.?? |
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I use a RCA connector for it and this eliminates most of the shorts issues. Actually I always use RCA connectors for most of my low power homebrew stuff. The only thing I check is that the outer of the connector makes a ground connections and so far have not had any issues. I use it even for power plug connection and it seems it handles well the current for the Ubitx. Il 18/mag/2018 22:45, "Ralph Mowery" <rmowery42@...> ha scritto:
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