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I've added a page to the wiki describing some steps for manual fault finding.

Could some of the users that have (had) problems with their HW have a look at this page and check if it helps them locating the probable faulty component(s)

?

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Designer of the tinySA
For more info go to

Yesterday I have executed the steps on this page. The hint regarding the 0 Hz vertical line is especially helpful. In my case, this vertical line is present, and as such, no complex repair is to being expected. The attenuation function is okay.

LNA is clearly defect and because the test signal shows only -55 dBm on the spectrum, the switch should be defective, too.

Thus I'd have to replace the switch and the LNA, not the attenuator.

Section Fault finding with oscilloscope:

I don't find L1 and L7 (HW 0.4.5.1).

BTW: I now believe what "LOW OUTPUT" on top of the screen means: the bottom connector, not something like low level voltage.

In general I se need to implement any changes to this page.

Rob

Hi Erik,

yes i performed the manual routine and think it is useful. I have a low signal level on my Ultra 407, down by 40 dB, i.e. at -75 dBm. Now your manual says that even with a bad RF switch, if the signal stays within 6 dB of that level when the LNA is enabled, then the LNA is fine. However, on mine, when i enable the LNA, it even goes up to where it should be, -35 dBm. Have you ever had this before ?

The manual testing of the attenuator behaves as it should, the noise floor goes up by as much as the attenuation, maintaining the level @30 MHz.

I ordered new switches.

My conclusion is that my switch makes a low impedance only when it is in normal (non-LNA) mode, and this is rather unusual because typically you expect it makes a low impedance in either position. I hope it is not the attenuator that causes the low impedance but else behaves normally in producing the correct relative levels ?

What you are observing is indeed possible as the switch can fail in?different ways

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--

Designer of the tinySA
For more info go to

Thanks. I inaugurated my cheap hot air station and the RF switch gently came off. Now i could jumper it to check the attenuator, but i prefer waiting for the spare part and soldering paste, and keep soldering on the board a minimum. Btw the accident occured with a unfinished homebrew LISN (TVS diodes didn't fit...), so it taught me that a transient limiter does make sense :)

"If the signal drops much more then 6 dB, or disappears completely, the LNA (U14) needs to be replaced."

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After the above comment following LNA test and before ATTENUATE test,?I think you need to instruct that the LNA be disabled since enabling LNA disables ATTENUATE.

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Peter