[Solved] HP 16500A Logic Analyzer Causes ELCB Tripping - Page 1
Forum section: electronics / repair

author: 1Ghz
author_rank: Unknown
timestamp: February 05, 2017, 11:52:46 am
content: Hello,I recently bought second hand HP 16500A Logic Analyzer.If I just turn on power supply switch, after ~70 seconds the ELCB tripped.I removed all modules except power supply module and microprocessor module, but still same.I checked my ELCB leakage current rating and it was 30mA.Can 16500A leakage current reach more than 30mA?If not how can I repair it?Thanks,

author: Armadillo
author_rank: Super Contributor
timestamp: February 05, 2017, 01:29:36 pm
content: The answer is NO and there is a unsafe leakage.Did you remove the display board. I suspect the High Voltage section.

author: free_electron
author_rank: Super Contributor
timestamp: February 05, 2017, 01:35:13 pm
content: Mains input filter. They have ero caps in em.

author: DTJ
author_rank: Super Contributor
timestamp: February 05, 2017, 02:02:11 pm
content: +1 for the power filter.

author: 1Ghz
author_rank: Unknown
timestamp: February 05, 2017, 02:44:59 pm
content: Quote from: Armadillo on February 05, 2017, 01:29:36 pmI did not removed color display module yet.I'll do next try.Quote from: free_electron on February 05, 2017, 01:35:13 pmQuote from: DTJ on February 05, 2017, 02:02:11 pmIf fault is power filter, should I replace whole power supply module? or replace some caps?AFAIK, there's no schematic for HP 16500A power supply.

author: DTJ
author_rank: Super Contributor
timestamp: February 06, 2017, 01:27:01 am
content: Does it have one of those IEC power inlet filter modules?https://www.google.com.au/search?q=iec+power+filter&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjGwIGlqPrRAhXCFpQKHbY9DK0Q_AUICSgC&biw=1920&bih=939

author: TerraHertz
author_rank: Super Contributor
timestamp: February 06, 2017, 05:02:49 am
content: Quote from: DTJ on February 06, 2017, 01:27:01 amYes, this is the likely culprit. Or, perhaps the power supply board has the filter there, as separate components. They will be right beside where the mains comes onto the PCB. One polyester cap between the A and N lines, and another two from the A & N to chassis ground (ie mains ground.) Those have probably gone leaky. Replace all three (and any others of the same kind you can see) with mains rated polyesters (modern ones) of same values.Btw, when those caps do go, they tend to burst into flames and produce the most god-awful stink, and an oily smoke that condenses on everything nearby and makes *that* stink too. It's a real bitch to clean.I'd suggest not turning the power on again until you have replaced those caps and/or mains input filter.

author: DTJ
author_rank: Super Contributor
timestamp: February 06, 2017, 05:19:07 am
content: Perhaps as a test (if it does have the IEC style input filter), disconnect the filter and bypass it.See if the unit then runs ok without tripping the ELCB.

author: 1Ghz
author_rank: Unknown
timestamp: February 06, 2017, 12:32:51 pm
content: Quote from: Armadillo on February 05, 2017, 01:29:36 pmI've removed color display power cable from power supply and still same.Quote from: DTJ on February 06, 2017, 01:27:01 amYes, it have IEC power inlet filter module.I've attached photo of it.Quote from: TerraHertz on February 06, 2017, 05:02:49 amThank you for your suggestion, TeraHertz.Quote from: DTJ on February 06, 2017, 05:19:07 amI'll test or replace it soon.

author: 1Ghz
author_rank: Unknown
timestamp: February 11, 2017, 11:21:08 am
content: I've replaced IEC power inlet filter module and test again, but after ~140 seconds it's still tripping the ELCB.I'll replace whole power supply module next week.

author: DTJ
author_rank: Super Contributor
timestamp: February 11, 2017, 02:38:11 pm
content: Bugger.Is there a chance that the leakage might not be too high but the sum of leakage on that circuit is causing an issue?Have you measured the earth leakage current? Is it high?

author: 1Ghz
author_rank: Unknown
timestamp: February 11, 2017, 02:57:35 pm
content: Quote from: DTJ on February 11, 2017, 02:38:11 pmNo, earth leakage current not measured yet. I'll measure it next try.

author: 1Ghz
author_rank: Unknown
timestamp: February 14, 2017, 12:49:09 pm
content: I've replaced whole power supply module today.It works like a charm.So problem is solved, but I was not able to repair faulty power supply module.I'll try to fix it later.Thank you all for your reply!

author: DTJ
author_rank: Super Contributor
timestamp: February 15, 2017, 01:06:18 am
content: Good to hear you got it going.