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Hi All,

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I am looking for some advice how to trouble shoot my Mid Band QMX.?

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Everything was working OK and suddenly I lost both RX & TX on 30m and 20m bands. There is no output but also BPF, LPF and SWR is totally off the mark when running checking procedures on terminal. For example BPF is -45dB while other bands 60/40 & 17/15 are -4dB. As I say other bands are working perfectly.

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I looked for broken connection or cold solder joint but all seems to be OK, as this was build unit by QRP-Labs team.

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Any idea where to look for the fault. Thank you.

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73 de Marek SP9TKW

Hi,

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I think I managed to trace a reason. LPF for 30-20 bands has intermittent break. When I remove display and control boards there is a connection. I put thibgs togeter and it works for 10-15minutes and then problem comes back. Also if I through all the bands all works well for 2-3 seconds and then its dead again on 30-20.?

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Plan is to refloat all LPF joints and hope that this will resolve the issue for good.

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73 de Marek SP9TKW

Hi Marek,

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the QRP Labs Wiki contains a document about the LPF section. Maybe it could help a bit.

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73 Ludwig

Marek

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Perhaps you solved it already. Note the coils are in series, so you can measure for DC continuity end-to-end. First place to assume is any man made solder connections, like here. Even rap lab techs are human, they are assembling lots of rigs. Enjoy your rig, even this opportunity lets you experience its components.?

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Curt wb8yyy

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Hi Ludwig,

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Yes I red document before, but I could not trace the problem as sometimes it was working sometimes did not. Anyway resoldered all connections for 30/20 LPF and issue seems to go away. I made since about 10 QSOs on different bands and various times with switch ON/OFF between sessions. All seems good.

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Thanks for your help.

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73 de Marek SP9TKW

Hi Curt,

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Yes, I was aware of that. As I said earlier problem was intermitent which was tricky to trace. All good now. Thanks for your help.

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73 de Marek SP9TKW