Agilent 54622A timing error + UPDATE problem came back - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: July 23, 2017, 10:50:50 am
content: Hello,It's been a while since my last "appearance" on the forum.Recently, I happened to get my hands on an Agilent 54622A scope which was in a rather bad need of TLC.So, I took it apart, gave it a thorough cleaning, put it back on and turned power on.The scope booted fine and all looked ok.I started playing with and, at some point, I also ran a self test, which completed ok.Following that, I played with it even more, which included working inside the unit (e.g. replacing the fan, measuring power supply voltages, etc.), sometimes with the cover off and no additional fan (I had not gotten to that page in the manual, at the time).Then, at some point, I decided to run a user calibration and, unfortunately, that ended in an error: Timeout oscillator.Rather confused and a bit panicky, I subsequently ran the self test again and, this time, I got an error here too: Timing chip test failed.Still, if I put in a signal in any of the two channels, all looks to be fine.Looking in the service manual, I don't see any details on the errors you can get from the self test or the user cal processes, not to mention where to look for faults in case of a given error.Anyone out there that could point me in the right direction, please?Thanks!

author: giosif
author_rank: Frequent Contributor
timestamp: August 01, 2017, 07:42:14 pm
content: BumpHoping someone can help me out with some information on this issue.

author: alm
author_rank: Super Contributor
timestamp: August 01, 2017, 08:07:50 pm
content: The closest thing you will probably find to schematics isthe HP 54600 CLIPwhich are for an older model. Maybe some parts of the block diagram and some sub-circuits are useful.Maybe you can find some helpful information in this video:

author: giosif
author_rank: Frequent Contributor
timestamp: August 01, 2017, 10:11:53 pm
content: Quote from: alm on August 01, 2017, 08:07:50 pmThat is a good idea.I'll have a look in the CLIP pdf's and watch the video as well.Thank you!

author: giosif
author_rank: Frequent Contributor
timestamp: August 04, 2017, 01:24:54 pm
content: So, I took the main board out for another inspection and gave it a quick brush again (using ESD-safe brushes).I then put it all back together, turned it on and checked the oscillators for outpt and all looked good.With some hope, I initiated the self test and... surprise... no errors anymore.Also, user cal completed fine with no errors either.Not sure what made the difference (maybe how the board was physically installed on its posts?), but I'm not going to try find out now.

author: alm
author_rank: Super Contributor
timestamp: August 04, 2017, 01:48:28 pm
content: Nice! Sounds like an intermittent contact. Your cleaning or the heat from running it with the case off might have caused it to go open. Could be either a connector or a bad solder connection or even a PCB trace/via. At least if the problem comes back, you know what to look for.

author: giosif
author_rank: Frequent Contributor
timestamp: August 05, 2017, 06:35:58 pm
content: Quote from: alm on August 04, 2017, 01:48:28 pmIndeed.Hopefully, I won't need to do that anytime soon.Thank you for the tips provided previously!

author: giosif
author_rank: Frequent Contributor
timestamp: August 05, 2017, 06:50:21 pm
content: Just an update on this, unrelated to the initial problem, but related to the device: the softkeys were not working properly, due mainly to the carbon layer on the actual keys wearing off.The small board normally sitting under the softkeys had also come loose, as the plastic fingers holding it in place had broken off (probably because the softkeys were not working properly anymore and the previous owner/s started pressing the keys harder and harder).So, I've thought of the different repair options and what you see in the pictures below is the result.On actual use, it seems pretty ok, but let's see how long it is going to last.

author: giosif
author_rank: Frequent Contributor
timestamp: August 07, 2017, 11:14:49 pm
content: Aaaannddd we are back to where we started: the error came back (I'm only running the self test at the moment): timing chip test failed.I added some new solder on the connection points of the oscillators, I supplied 3V to the battery terminals (only for the duration of the self test), I even de-, then, re-soldered one of the relays, wiggled the board, twisted it, tapped it, you name it.This time, the problem doesn't want to go away.UPDATE: One thing to mention, though is that if I switch to single shot, it triggers immediately, irrespective of where the trigger level is set.Not sure if this would happen also when the timing error is absent, but at least it is showing up now.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 08, 2017, 01:59:33 am
content: Not sure how much do you like it and how much do you want to invest in it but.. I found "parts" unit for you. I think it's a new listing so maybe it's an option and you can just put two of those together. Or keep yours for parts and use the other one, the screen seems to be a bit out of focus on the one on ebay but it maybe just settings.http://www.ebay.com/itm/HP-Agilent-54622A-2-channel-100-MHz-Oscilloscope-/282602264097?epid=96932002&hash=item41cc685621:g:e~4AAOSwB-1Y4~OU

author: giosif
author_rank: Frequent Contributor
timestamp: August 08, 2017, 07:22:58 pm
content: Quote from: Ordinaryman1971 on August 08, 2017, 01:59:33 amThanks for looking up a replacement for me!However, at $200 price for the unit (and shipping would be a further $255), I think I'd rather live with the fault for now until I get enough drive to look for the fault again and attempt a repair.

author: BC7333
author_rank: Newbie
timestamp: August 10, 2017, 10:34:50 am
content: I used these new conductive rubber buttons to fix most of my 54662 non working buttons. Still have a problem with two buttons but seems unrelated to the switch itself. Appreciate any tips from anyone following this thread to resolve my remaining button issue. It's athttps://www.eevblog.com/forum/repair/agilent-54622a-pulsewidth-and-modecoupling-buttons-not-working/msg1277566/#msg1277566http://www.ebay.com/itm/Rubbers-for-Remote-Controllers-Conductive-Rubber-Pads-Pack-of-100-/111943306278They are slightly bigger than the originals.

author: giosif
author_rank: Frequent Contributor
timestamp: August 10, 2017, 07:33:36 pm
content: Quote from: BC7333 on August 10, 2017, 10:34:50 amBefore going down the path of using the push switches, I was looking at exactly the same product.After some consideration and reading of other people's stories, I decided for the switches.On your problem with those two switches, I would trace the... erm... trace... on the PCB that is common to these two buttons to see if there is any broken/corroded paths.Or maybe there is a problem with the connectors and/or cable linking the front panel to the main board?

author: BC7333
author_rank: Newbie
timestamp: August 11, 2017, 04:14:25 pm
content: Thanks giosif!Yeah, as time permits will begin tracing. If all else fails might try your button trick. As a test, I stuck two of these new dots on a plastic tweezer, and used them to make contact direct with the board switch pads. Worked on all except for these two :-/ so doubt it would help. Might try with some aluminum foil.. the rubber dots do have a couple hundred ohm resistance with meter probes it seems, that, of course, should go way down as more surface area makes contact. I didn't really want to do it so far in case 0 ohms might in some way cause damage. I guess your switch trick excludes that possibility.