LeCroy 9361 - SY_Error: PC b0f74 vector 2 lvl 0 fmt B - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: July 20, 2019, 06:53:15 pm
content: Hello,Not too long ago, I purchased a LeCroy 9361 scope that gets stuck during boot displaying the error message in the subject line.Doing a bit of digging and reading the messages in the LeCroy owners group on groups.io (as well as the older group on Yahoo), my initial thinking was it may have to do with the RTC battery going flat.However, upon replacing the battery, there is no change in behaviour (and the new battery is good).Next thing I did was to measure voltages: first, on the power supply, then on the voltage regulators on the main board and each output is as expected.Now, the interesting thing I've noticed is that, as the scope starts up, it will very briefly display a message at the top of the screen, before showing the SY_Error... message.I had to record a video of the startup process to determine the actual message and it is "OVERLOAD on External Trigger Input".Anyone has seen this type of message before?I already did a visual inspection of the external trigger input section on the board, but I am not seeing anything suspicious.Any tips where to look and what to check next, please (a service manual would have been handy in this situation)?I should mention I've asked the same thing on the LeCroy owners group, but it seems to be rather silent these days.Thanks!

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 21, 2019, 12:25:51 am
content: I saw your question go by on groups.io too.I don't think the 9361 schematics are around anywhere. (other than the PSU that AFAIK is common to the 930x, 931x)I've never owned a 9361 but they are like the 9362 or Tek TDS600 scopes with a fast CCD sampling then slowly clocked out to a modest ADC.The 9361 may share some common components with the 9310, hopefully the analog frontend and trigger IC's. (The service manual is available.)Could you post some detailed photos of the PCB that could give some clue to how things ate tied together.A not so uncommon problem is failure of an analog MUX between the DAC that generates the various control voltages and the components these control voltages are meant to reach. (Output stuck high to trigger level control or offset compensation voltage.)On other 9300 models the scope will self calibrate on powering up, if the calibration signal that's switched-in to the F.E's (can't remember if that's square or DC) is stuck too high it could lead to some error, not sure if that would come out as an overload or Cal error though.FE and Trig circuitry should be identical between channel inputs and ext. trig. Assuming the problem only hits the ext. trig you should be able to do some comparative probing.Are you able to access the maintenance menu and read the error logs?

author: giosif
author_rank: Frequent Contributor
timestamp: July 21, 2019, 03:32:05 pm
content: Quote from: shakalnokturn on July 21, 2019, 12:25:51 amJust my typical "luck".Quote from: shakalnokturn on July 21, 2019, 12:25:51 amAre you sure it's the 9310 you meant?I can't seem to find the service manual for that model.Maybe you meant 9320 instead (in which case the ext trigger input differs from the 9361)?Quote from: shakalnokturn on July 21, 2019, 12:25:51 amSure. Please see below (for the close up on the external trigger input, please don't mind the missing op-amp and transistor - the green rectangle areas - I removed those as part of the troubleshooting, but that made no difference to the error on the screen).Quote from: shakalnokturn on July 21, 2019, 12:25:51 amHmmm... Thing is, at this point in time, I am not convinced there is anything wrong in the external trigger input and a communication path issue is something that did cross my mind.However, I have no hard data to support this.Quote from: shakalnokturn on July 21, 2019, 12:25:51 amAmm... I'm not sure of that, but happy to be proved wrong, based on the pictures attached.Quote from: shakalnokturn on July 21, 2019, 12:25:51 amNo, but maybe because I didn't know how to get there.Is it based on a combination of soft keys being pressed at power up?Or is it by navigating through the various menu options?If the former, I don't know the key combination for that (so far, I've tried only soft reset and hard reset key combinations).If the latter, as I mentioned before, the scope gets stuck in the boot process and there is no menu/option to select.Thanks!

author: dietert1
author_rank: Super Contributor
timestamp: July 21, 2019, 08:42:18 pm
content: Having some experience with 93xx scopes, i would guess the error message means the CPU board is not running stable. The message says something like an unexpected system event happened. But when the screen is up, the error occurs after millions of successful cycles. Your scope is very close to working and these scopes in general are rock solid. I mean a severe problem like a tantalum cap short appears completely different.Considering the age of the scope, i would first renew all electrolytic caps. There seems to be one on the aquisition board, others are in the power supply. Then reseat all components with sockets, including all cable connectors, including the ones inside the power supply. Then a detailed optical inspection of the CPU board, looking for uneven solder joints. I once found a bad solder joint of a SMD resistor in the analog front end after a one hour search using a microscope. Resoldering fixed an annoying calibration error message. I would also try to get a second scope of same type. This will help to keep both of them running.Regards, Dieter

author: giosif
author_rank: Frequent Contributor
timestamp: July 22, 2019, 12:13:32 pm
content: Thank you for the suggestions, Dieter!I will proceed with the checks, as you mention.In the meantime, anyone with other ideas/comments, please feel free to chime in.Quote from: dietert1 on July 21, 2019, 08:42:18 pm

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 25, 2019, 08:51:37 am
content: Things common to other models that I went to the bother checking on the service manuals:CPU2 board (all the 9300 family but different firmware on the 936x)PSU (9304, 9314)MFE409 (9304, 9314...)MTR408 (9304, 9314...)HSH410 (9314)SP97508B (9304, 9314)MDX407 (9304, 9314)MTB411 (9304, 9314)MCL404 (9304, 9314...)Very likely although I was unable to confirm:MST412 (9304, 9314...)So you just get a little extra with a squeezed in CCD per channel and some decoding and control for this extra subsystem. (TQFP IC with small tall heatsink.)I hope you won't have to dig into all this anyway... If Dieter is right there are CPU2 boards going on evil bay, then the problem is getting the right firmware on them.

author: giosif
author_rank: Frequent Contributor
timestamp: July 27, 2019, 04:30:22 pm
content: Quote from: shakalnokturn on July 25, 2019, 08:51:37 amThank you for looking into that!So, looks like a lot of things in common with the 9304 and 9314.But do you happen to have the service manual for any of these models?I've had a (quick-ish) check on the CPU board, but I'm not convinced the issue is there.Instead I think the problem might lie on the main board, in the area where the CPU board plugs into the main board.The inside of this scope was rather dirty when I got it, with dust that was stuck to the main board (which would indicate there must have been a combination of dust and humidity at some point).OTOH and surprisingly enough, the CPU board looked rather clean.So, I suspect something(s) has corroded on the main board.Will investigate and report back with any findings.

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 29, 2019, 10:09:27 am
content: http://www.ko4bb.com/manuals/77.136.217.35/LeCroy_9314AX-CX_Service_Manual_A.pdf

author: giosif
author_rank: Frequent Contributor
timestamp: July 31, 2019, 06:40:41 am
content: Quote from: shakalnokturn on July 29, 2019, 10:09:27 amAh! How could I miss that?Apologies, I must have been temporarily blind or something!This manual is great and, on a quick read, it seems to match with most of what I have on the main board.Nice!I need some time to read and digest the information, but it's looking positive.