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Fault Finding for the tinySA Ultra / Ultra+

This page describes how to find what is wrong with your tinySA Ultra for the most common problems.

Black screen after firmware update

You either loaded an incorrect firmware or the loading did not complete. See the firmware updating guide for how to retry loading a firmware.

UI hanging or no data shown

If the screen shows the user interface but no scan and/or is not reactive to touch there may be a problem with the LCD touch.

• Push the jog button to the side and restart the tinySA. If this does not help do the next step
• Unscrew the 4 case screws a bit as due to manufacturing tolerances a small amount of cases touch the LCD screen. If this does not help do the next step
• Take the tinySA out of its case by removing the 4 case screws and reinsert the LCD cable by gently lifting the black bracket, removing the cable, inserting the cable and pushing the black bracket down to secure the LCD cable
• There has been a very small number of LCD cables with out of spec connector spacing. Often it is still possible to get the device back working by careful positioning the cable in the connector.

Self test fails

The built-in self test does all these tests but doing them manually can give a quick indication of what component(s) to replace.
Start by restarting the tinySA while holding the jog button pressed to the side. The tinySA starts with all factory defaults and level indicators at the top and bottom left turn red
The screen should look like below picture with a yellow line going up from the noise floor to 0 dBm at zero Hz

If the yellow line at the left is absent or goes up only a bit, as can be seen in below picture, either the mixer or the LO is bad. There is no easy repair for this but luckily this problem is very rare.

Next step is to connect RF and CAL connectors using a short SMA cable and enable MODE/CALIBRATION OUTPUT/30 MHz and go back to spectrum analyzer mode.
The screen should look like below where the marker at 30 MHz may deviate maximum 4 dB from -35 dBm

A first indication something is wrong is when the indicated level deviates more then 4 dB from -35dBm like seen in picture below. If the difference is 5dB or more, the input switch (U22) needs to be replaced.

Now activate the LNA using LEVEL/LNA. The noise floor should drop about 20 dB and the indicated level may change up to 6 dB
Even with a bad switch, if the measured level with LNA on stays roughly the same, the LNA is fine as can be seen in below picture.

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

If all above tests are OK, switch off the LNA and set the internal attenuation to 2, 4, 8 and 16 dB (see picture below). With different settings of the attenuation the noise floor should go up but the level indicated by the marker should stay the same within +/- 1 dB If the measured level with changes of the attenuation changes more then 2 dB the attenuator should be replaced

These are the components that may have to be replaced:

• Input RF switch U22: XA17-G4K or AS179-92LF
• LNA: for ZS-405 and zs-406: BGA2817 (U14), for ZS-407: ZK10D (U12) (see https://www.zeenko.tech/mmics )
• Attenuator U28: PE4312C-Z

All these components are located under the removable shield next to the RF connector. Power down the tinySA before removing the shield.

Fault finding with oscilloscope

When you do have a oscilloscope you can trace the output signal in generator mode from the mixer to the RF connector and check the levels. With the generator set to 10 MHz and maximum output power you should see about 180 mVpp on the following components.

• L7 under large shield between connectors
• L1 idem
• C24 under shield next to RF connector: No or strongly reduced signal means bad attenuator
• C58 idem: No or strongly reduced signal means bad switch

Using an oscilloscope and the CAL output at 30 MHz you can trace the input signal from the RF connector into the mixer by probing at these locations. WARNING: The level is rather low, about 10 mVpp

LNA not active:

• C58 : Input signal at connector
• C24 : After the switch, if no signal the switch is bad
• L1 : after attenuator, if no signal the attenuator is bad
• C35 under shield next to RF connector: There should be no signal

LNA active:

• C58 : Input signal at connector
• C35 : After the switch, can be a bit lower
• C34 : after the LNA about 140 mVpp, if no or much weaker signal the LNA is bad.
• C24 : There should be no signal