N1201SA antenna analyser failure

[okz00k]

A little over 1 year ago I purchased my favourite tool - a N2101SA vector impedance analyzer. Its a pocket size device which does just about everything I have ever wanted for tuning the VHF and UHF antennas I build and checking resonance of commercial antennas I use. I love this device. When it is working properly it gives me great graphical view of antenna resonance over the frequency ranges I'm interested in. Below are a couple of pics when it was working.

[okz00k]

After three months in the drawer the battery was low and it would not turn on. After charging the battery, now the device just provides a messy response, with no resemblance of the antenna connected to its SMA connector. It now displays dips and peaks a few MHz apart, continuously across the entire spectrum. Display is the same if a 50ohm dummy load is connected or if the antenna connector is left open circuit, although the position of some peaks change when the dummy load is attached.

I have reset the device without effect. Battery voltage is 4.13v

I purchased the device from Banggood and they will not accept a warranty return after 12 months. I cannot find contact details of the manufacturer AAI (Accuracy Agility Instruments) Any thoughts on how I might restore the proper operation of this device will be greatly appreciated.

[RCinFLA]

Schematic made from photo of PCB

[mikerj]

Do you have a 50R dummy load to try it with?  I'm wondering if it managed to corrupt it's calibration when the battery died, the instructions have a section about what to do when it completely locks up, so seems like they expected that to happen

The instructions also have details of calibrating the device, though I would advise dumping the serial flash device that holds the cal data before you do that. One of the many cheap programmers should handle that if you have one.

Looks like a very neat little tool (when it's working!).

[okz00k]

Problem solved. The device simply needed to be re-calibrated. I selected the Calibration option from the menu and followed the prompts.  For calibration you need:
- open circuit
- short circuit, and
- 50 ohm dummy load.

I'm so pleased to have my N1201SA working again.

[izmile]

Old post.. but might be useful for someone in future.

I had the exact same issue and found that U4 (3V3 linear regulator) was faulty. Replaced it and it works fine.