Hi, recently acquired a 10 year old HP 8558B Spectrum Analyzer. Everything seems to be working except the display. At first there was nothing, after leaving it plugged in for a while then turning it on, the display worked and it had 2 lines but then it went dark again. What could be happening and how can I fix it?

 

I hope that you got this for free. If not, demand your money back. HP is very good with their product support, so you could purchase the service manual if you wished. Or, they could repair it for you. Usually, with a dim display it means the HV supply is not working properly.

Without the display, how do you know that everything seems to be working?

 

I hope that you got this for free. If not, demand your money back. HP is very good with their product support, so you could purchase the service manual if you wished. Or, they could repair it for you. Usually, with a dim display it means the HV supply is not working properly.

Without the display, how do you know that everything seems to be working?

Yes I got it for free and the full manual is online. (https://literature.cdn.keysight.com/litweb/pdf/08558-90102.pdf?id=814558)

When it works briefly I can see the Signal from a strong radio transmission near it. Will HP repair something This old?

 

Not unusual for leaky caps in HV supply to drag down HV supply V.

Also many used diode cap multiplier circuits to generate HV that would fail.

If analyzer in dirty environment cleaning, especially if around smokers,
can help.

I am guessing HP cannot service this as most parts in it probably
obsolete.

Make sure you discharge CRT before cleaning -

Google this to make a probe for this purpose, "diy discharge probe hv crt"

Lastly do not use metallic tools around CRT glass, they are pretty fragile
and under a lot of stress due to vacuum drawn inside them. Safety glasses
mandatory.

Regards, Dana.

 

Not unusual for leaky caps in HV supply to drag down HV supply V.

Also many used diode cap multiplier circuits that would fail.

If analyzer in dirty environment cleaning, especially if around smokers,
can help.

I am guessing HP cannot service this as most parts in it probably
obsolete.

Regards, Dana.

Yup it was full of dust from where I got it from. I will open it up and check for loose connections and clean it then retest.

 

You can make gpib controller using Arduino uno and a cheap gpib cable. This way you can connect analyzer to pc and get the readings without using the screen.

Often enough the data over gpib is more complete then what native screen would show.

 

Sounds like a cool project, will look into it. Why are GPIB USB cables so expensive?

https://www.thedebugstore.com/smart488-gpib-interface-alciom.html

 

Why are GPIB USB cables so expensive?

It requires a custom circuit to convert the USB serial protocol signal to the GPIB parallel protocol and not that many of them are sold.

Here's some possible cheaper alternatives.
The one from Prologix at $150 may cost less than fixing the display on the analyzer.

 

Something a little cheaper -

https://egirland.blogspot.com/2014/03/arduino-uno-as-usb-to-gpib-controller.html

Regards, Dana.

 

Something a little cheaper -

https://egirland.blogspot.com/2014/03/arduino-uno-as-usb-to-gpib-controller.html

Regards, Dana.

That’s the one.

 

Something a little cheaper

But not exactly off-the-shelf.