HP 8566B - Page 1
Forum section: electronics / general

author: bat
author_rank: Regular Contributor
timestamp: August 30, 2024, 12:13:57 pm
content: Hi y'allYesterday, I attempted to test a HP 8566B spectrum analyzer that was stored for years. Upon starting the analyzer, the CRT display felt off, in fact the electron beam shows that the sweeping was pretty much dead. So I knew something was wrong with the CRT from the get go.I put the unit on standby and took my phone to record myself starting it up again. While I was setting my phone to record, I heard arcs coming from the unit, I unplugged everything and very white smoke with a foul smell showed up.I already had this issue with a tektronix 2455, CRT power supply grilled, had the same smell and smoke.Now where is this issue coming from ?Well... i'm not 100% sure but, this HP 8566 used to be at a casablanca factory, in morocco therefore, I suspect that the salty + eventual humidity collected into the CRT which created arcs and the PSU blew up. Oddly enough, my tektronix 2455 also came from the same place.I will tear down this equipment and check whether it's worth it to repair or not.What do you guys think ? Am I stretching the hell out of this theory ?

author: jmelson
author_rank: Super Contributor
timestamp: August 30, 2024, 03:03:38 pm
content: White smoke and strong smell make me think of electrolytic capacitors. There should be obvious signs of venting stuff from these units once you open it up.Jon

author: bat
author_rank: Regular Contributor
timestamp: September 10, 2024, 10:24:20 am
content: Well yes, capacitor died. I removed it and booted the analyzer up just to see what would happen. The CRT didn't power up at all. Nothing seemed to be dead. I will check the high voltage PSU for the CRT later.

author: squadchannel
author_rank: Frequent Contributor
timestamp: September 10, 2024, 10:36:18 am
content: picture it looks like the main input panel.I think it is a type with an integrated filter.It is definitely a RIFA cap. It is to be replaced immediately.

author: bat
author_rank: Regular Contributor
timestamp: September 10, 2024, 10:59:55 am
content: Quote from: squadchannel on September 10, 2024, 10:36:18 amWhy do they fail so much ? I had 2 equipment where the RIFA capacitor failed. Is it because they get older ?

author: squadchannel
author_rank: Frequent Contributor
timestamp: September 10, 2024, 11:08:41 am
content: RIFA cap absorb moisture over time, resulting in loss of insulation and explosion.most cases, the molded epoxy will crack.In my case, if RIFA is used, no matter how new/used, I immediately replace it with TDK X,Y rated capacitors.

author: bat
author_rank: Regular Contributor
timestamp: September 10, 2024, 11:49:07 am
content: Quote from: squadchannel on September 10, 2024, 11:08:41 amInteresting. I have a tektronix 2465 stored that hasn't been turned on in years. I will change the RIFA capacitor before turning it on.

author: tggzzz
author_rank: Super Contributor
timestamp: September 10, 2024, 01:54:52 pm
content: Quote from: bat on September 10, 2024, 11:49:07 amIf you don't, youwillchange itafterturning it on - and maybe the series resistor as well, but there's no need to replace the PCB's prepreg under the resistor. Unsurprisingly, I speak from experience.

author: coppercone2
author_rank: Super Contributor
timestamp: September 11, 2024, 04:20:28 am
content: take it all apart and inspect it all

author: bat
author_rank: Regular Contributor
timestamp: June 12, 2025, 03:09:05 pm
content: I am returning to my spectrum analyzer once again, I don't have alot of time to work on it but since I do not own a copy of the service manual, I was looking for a capacitor replacement on the AC filter, does anybody have some for sale ?