Products > Test Equipment

HP 8566B - Is this bad or no?

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W4PJB:
Hoping for a quick answer. Looking at an 8566B, condition unknown. Is this screen bad? Or is this normal for one powered on but with nothing attached?

I would expect just a straight line of static on the noise floor, but perhaps this is normal?

TerrySt:
Normal. 

W4PJB:
Thank you!

G0HZU:
Yes, I agree that that stepped response in the noise floor is normal. 

Also have a look on a 5MHz and 10MHz span to see how much wobble there is on a signal fed into it at the centre frequency (eg 70MHz CF and 5MHz span)

Some units can be very wobbly when tested like this although a small amout of wobble is normal I think. The wobble should stop on spans less than 5MHz.

My only other comment about the display is that the CRT needs adjusting. The graticule is blooming (fuzzy) compared to the signal trace. Mine was like this (horrible) and I replaced a resistor in the Z board and also readjusted it for a nicer display.

I've linked to a hi res image of it below. This shows how nice the display can be if it is adjusted properly. I did this about 10 or 11 years ago so I can't remember what I replaced on the Z board but the CRT changed from a gloomy fuzzy mess to what you see below. It actually looks nicer than this when viewed with the naked eye as the camera makes it look a bit flat and dull.




G0HZU:
If you are looking to buy one, make sure you are happy with the amount of fan noise these analysers produce. In a fairly small room in a typical house the noise will be difficult to tolerate for long periods, especially if there is nothing else noisy in the room. They really are very, very noisy especially if the fans are worn as they can also make a slight clattery sound. The RF section has a huge fan at the rear.

You will also need a really sturdy bench or trolley to put it on. I think it weighs about 50kg. I don't use mine very much since I upgraded to a modern instrument. I really don't miss it at all because of the fan noise and the amount of bench space it took up.

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