Blown frontend of a Siglent SSA3021X Plus

[wemme]

Here is another Siglent Spectrum analyzer repair post.

I was doing some conducted emissions testing and noticed I was getting some rather screwy results even thought being very careful with clamping the input during power transitions of the DUT.

Linking the tracking generator to the RF in port with a N - N cable confirmed that the front end of the spectrum analyzer was damaged with a large hump below ~1.5MHz and well down in level through out the rest of the spectrum. Pulling the analyzer apart I found an Analog Device's HMC1118 RF switch and some DNF diodes instead of the RF pin diodes and RF switches that are usually seen on siglent analyzers. I ordered a new chip which arrived in a few days and reworked the the PCB. The board was more difficult to rework which I put down to the rogers PCB material having a higher thermal conduction than normal FR4.
Much to my delight on reassembling the unit the output was level across the spectrum at -20dBm
I must say I have found the siglent to be a good spectrum analyzer packed with great features and easy to work on.

Regards
Bart

[tautech]

Congrats on your repair and for others to find in the future I should link this one here too.
https://www.eevblog.com/forum/testgear/what-happens-when-you-blow-the-input-of-a-6500-siglent-ssa-3075x-plus!/

[F4FEI]

Hi Bart,
Thank you for your very interesting post.
I am facing the same problem with my SVA1032x which has the same input circuit.
So I will try to change the HM1118.
As tools, I have a hot air gun, flux, low temperature welding, a thermocouple, antistatic gloves and bracelet.
What advice could you give me to make this operation a success?
Thank you in advance.
Dominique