HP 8566B - Is this bad or no? - Page 1
Forum section: electronics / testgear

author: W4PJB
author_rank: Regular Contributor
timestamp: May 14, 2024, 09:28:11 pm
content: 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?

author: TerrySt
author_rank: Regular Contributor
timestamp: May 14, 2024, 09:56:35 pm
content: Normal.

author: W4PJB
author_rank: Regular Contributor
timestamp: May 14, 2024, 09:57:52 pm
content: Thank you!

author: G0HZU
author_rank: Super Contributor
timestamp: May 14, 2024, 11:27:29 pm
content: 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.

author: G0HZU
author_rank: Super Contributor
timestamp: May 14, 2024, 11:46:46 pm
content: 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.

author: shabaz
author_rank: Frequent Contributor
timestamp: May 15, 2024, 01:17:27 am
content: Same experience here! I have an even older 8558B, it sounds like a rocket taking off, completely unusable in my home environment : ( It was an ebay purchase, I used it briefly, and has been in the shed for the past 10 years. Very easy to crush fingers with it too, due to the weight when taking it out of it's massive hard suitcase (which looks as if it's from a Mission Impossible movie or similar; military green!).

author: W4PJB
author_rank: Regular Contributor
timestamp: May 15, 2024, 01:30:06 am
content: Thanks everyone for all of the replies, they are very helpful! This unit was in a local eBay auction from a seller that typically sells everything as "parts only, untested" but from the screen it appeared to work.I didn't bid, and it didn't sell, but I'm going there tomorrow anyway to pickup another item so I'll talk to them about it. Honestly it's not something I need as I already have an Anritsu MB-2712B 7ghz portable analyzer, but there's just something "cool" about these old boat anchors, and hey, never know when I'll need to measure 22ghz

author: G0HZU
author_rank: Super Contributor
timestamp: May 15, 2024, 05:57:39 am
content: Bring a BNC cable and a BNC to N adaptor with you and connect the main RF input to the 100MHz cal output on the front panel. Then press the blue SHIFT key followed by FREQUENCY SPAN. It will then do a series of automated correction tests which it should pass. Also check the attenuator works on all settings. The chances are you will have to deal with Yig related issues at some point. Only buy one of these if you are prepared to take it apart and replace tired caps and deal with intermittent issues caused by the plug in cards.Make sure it works OK above range 0. The higher ranges use a different and very exotic mixer above 2.5GHz.

author: G0HZU
author_rank: Super Contributor
timestamp: May 15, 2024, 06:19:07 am
content: If you switch it on from cold, it will report OVEN and REF UNLOCK issues onscreen. This is normal as you are supposed to leave it powered in standby for maybe 10 minutes to allow parts of the RF section to warm up in standby first. However, l’d recommend turning it on from cold just to see how it copes with a cold start.