Rotten Coax Cable in 22GHz HP8562A Spectrum Analyzer - Page 1
Forum section: electronics / repair

author: Jamie_A
author_rank: Contributor
timestamp: December 04, 2023, 05:32:24 pm
content: I'm restoring a HP8562A Spectrum Analyzer, which other then some bad capacitors works perfectly. Calibration seems to be great.Unfortunately ALL of the (low frequency) SMB cables have their outer insulator rotten. See the pictures. They have all crumbled. They shed tiny strands of metal from the outer conductor.All of these will need to be replaced. Has anyone done a similar repair?I'm considering using some inexpensive LMR100 coax and right angle SMBs. Any idea what HP would have used originally? Hopefully replacing these won't impact the calibration too badly.

author: Swake
author_rank: Frequent Contributor
timestamp: December 05, 2023, 07:47:28 am
content: Replacing this with 'cheap' stuff? No no no no, don't do that.I would even avoid to unplug these. Admittedly I'm a bit paranoid when it comes to these things. But ok, that might not be all that realistic.Remove what comes apart easily then fit them a new layer of isolation with some high quality tape.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 05, 2023, 11:45:29 am
content: Or maybe the smallest 3:1 heat shrink that will fit over the connectors after removing the rotten plastic?

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 05, 2023, 11:46:43 am
content: Quote from: Jamie_A on December 04, 2023, 05:32:24 pmit is just cosmetic, if they still work, leave them be. save your time or you could regret trying to replace them..

author: coppercone2
author_rank: Super Contributor
timestamp: December 05, 2023, 12:10:43 pm
content: I don't think you should be scared to replace a coaxial line. its not even hard line. just get good coax from pasternack or somethingit might be a little expensive but that insulation is BS and should not be kept aroundget the OD crimp tool, solder interior pin (preferably with hot tweezers or hot air not to get solder on the connector) and remake the cables if you can't buy something close enough ready made. the only thing it is is a bit expensive.I replace things like this but with not cheap brands.What is to say the dielectric in the cable is in a good state if that happened to the insulation??if you simply cannot afford it, buy very high shrink ratio heat shrink and recoat it. might take trial and error.just be warned replacing the cable takes some planning and engineering, you can't just wing this

author: xrunner
author_rank: Super Contributor
timestamp: December 05, 2023, 12:40:49 pm
content: Quote from: Jamie_A on December 04, 2023, 05:32:24 pmI've made up SMB coax replacement cables so yes absolutely you can do it!Just collect the new parts and get a crimper for the right size coax and connectors you are using if you don't have one already. It's not too difficult. I show the old cables I needed to replace and the new parts and cables I made.

author: Jamie_A
author_rank: Contributor
timestamp: December 05, 2023, 12:51:18 pm
content: Thanks for the good suggestions! I had no idea that I could buy a higher shrink ratio tubing (3:1). I see some are adhesive lined too. I'll do that as a temporary measure until my coax ships in.I'll go ahead and try doing the full cable replacement. Roughly matching each cable to length and doing a quick check for insertion loss on each. I'd feel bad leaving in the old ones and risking the outer conductor strands shorting something out internally. Many of them were close to shorting stuff out already.I believe the highest frequency is the 600MHz 2nd LO. Otherwise most of them are <10MHz, and narrow band. Hoping replacement will just result in a very slight constant amplitude offset.

author: coppercone2
author_rank: Super Contributor
timestamp: December 05, 2023, 12:55:30 pm
content: the adhesive lined is like not flexible it will be like putting a rubber hose in therethe amount of cost of trying to find a replacement board or something will be nothing compared to just getting the tools to do it right.

author: Jamie_A
author_rank: Contributor
timestamp: December 05, 2023, 12:58:35 pm
content: Ah okay that would have been a failure, these need a pretty tight bend radius. Thanks for the warning. That's actually why I was considering LMR100 over RG316. Seems like it's rated for much tighter bends.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 05, 2023, 02:09:32 pm
content: Maybe this fellow might have appropriate cables, He does have SMBhttps://groups.io/g/test-equip-trader/message/11980