Damage RF input on spectrum analyzer

[neutrino]

During a measurement on a PCB with high and low voltage, an unexpected and unpredictable failure,
connected the mains voltage (220Vac) in RF input on my spectrum analyzer N932OB AG**ENT. I suppose the damage is (obviously) really serious. I am waiting next week to contact a service. I am very worry. Can someone tell me how the damage is serious? The instrument does not turn on. HELP!

Best regards

 

[biff44]

The instrument does not turn on. HELP!

Best regards

Yep, that is always a bad sign!

Check the fuse...maybe you just popped it with high ac leakage currents.

You need to come up with a system, in the future, that isolates the spectrum analyzer (both the connector center conductor AND the outer conductor) from the large voltage. Since the AC voltage is very low frequency, a differential highpass filter would be a bare minimum. Then a microwave attenuator, followed by a diode limiter would be nice.

It happens to the best of us. I blew out the front end of a spectrum analyzer once measuring the output of a high power comb generator. The comb tooth I was looking at was only +5 dBm. The problem was there were around 80 more comb teeth not shown on the screen of similar power that were all adding up! A costly repair!

 

[E-design]

Not turning on - hopefully a blown fuse, BUT probably blown the input attenuator or worse the input mixer as well.
Can be a very costly repair from my experience repairing similar equipment in the past.

 

[vfone]

There are big chances the RF input survives (because the AC mains power loop close through the ground), but definitely the internal switching power supply of N932OB dies.

 

[neutrino]

Thanks to all. You give me hope of not having to throw it all away.

I don't understand the reason why the line voltage (220Vac) of my tested PCB passes from RF INPUT connector to internal switching power supply (and RF input survive) ...

 

[neutrino]

Thanks to all. I connect the instrument main supply to AC main network. After one hour I turned on the instrument. It seems to work properly. After calibration, all
work fine. I am very happy!

I think at the time of the fault, the instrument is going into protection. A colleague remembered that when we bought the instrument, at the first power on, the instrument lit after one our.

Regards.

 

[biff44]

Indeed, the microwave gods have smiled upon you today. As an offering to them, at the least I suggest installing one of these in between your 220V circuit and the spectrum analyzer:

DC Blocks - RF, Cables, Video Cables, RF Parts, Connectors

In your case, the inner/outer block. Ask them how many volts it is good for, you might need 2 in series!

 

[neutrino]

Indeed, the microwave gods have smiled upon you today. As an offering to them, at the least I suggest installing one of these in between your 220V circuit and the spectrum analyzer:

DC Blocks - RF, Cables, Video Cables, RF Parts, Connectors

In your case, the inner/outer block. Ask them how many volts it is good for, you might need 2 in series!

Thank you!! I was very lucky and I will treasure what happened. I'll buy two DC block (working voltage 200V each) connected in series to the RF spectrum analyzer.