LeCroy 9314 - Page 1
Forum section: electronics / testgear

author: Nick
author_rank: Newbie
timestamp: January 15, 2014, 12:12:23 pm
content: Hello folks,I am owning a LeCroy scope (9314AL) which has a startup problem. Even having the service manual for the unit and the additional information for the CPU3 processor board I am quite unsure where to look at.The symptom is as follows: switching the device on the fan starts blowing, but the screen remains dark and no start up beep can be heard. After several minutes it starts as it should do at the very beginning.Even after having had a look into the (self) test menu, I am unsure where to look at since nothing seems to be unusual. Here I have a second issue: can anyone supply an information or document covering the (self) test menu in depth?Best regards from Nick

author: ElektroQuark
author_rank: Unknown
timestamp: January 15, 2014, 02:32:52 pm
content: Power supply. It looks a capacitor problem that inhibites PSU start till it's warm enought. Check them.

author: Nick
author_rank: Newbie
timestamp: January 18, 2014, 03:15:37 pm
content: Folks, finally I experienced a more severe issue on the above mentioned scope I will have to care for first.Running the self test it reports trigger threshold and hysteresis errors on all channels including the external one. Based upon the service manual today I have tried to calibrate it - but nothing changed! I have attached 4 pictures that were taken:1. The test bench with the front panel of the scope removed using longer cables to connect the CRT and keyboard PCBs. Also as mentioned in the manual I have added a fan to cool it since the internal one can not work as intended.2. The diagnostic summary showing that the trigger is not working on any channel including the external input3. The detail result of trigger from channel 14. The detail result of trigger from the external input.Even having tried to calibrate it as mentioned above, no value (1/2/3/4/ext) did change.Thinking about the internal functionality of the scope with the circuit diagrams in hand I had the idea that not the analog circuitry might cause the problem but digital ones: not only the testing stimulus is created from these but also D/A converters assign trigger levels. I have looked for soldering shorts since the battery had been changed from the previous owner - but I could not find one.The diagnostic menue offers much more testing information: does anyone have an information of these?Your feedback and thoughts would be appreciated very much. Thank you very much in advance.Nick

author: nctnico
author_rank: Super Contributor
timestamp: January 18, 2014, 03:27:17 pm
content: Did you check the capacitors in the PSU as EdoNork suggested? The diagnostics menus are not going to magically solve the problems!

author: Nick
author_rank: Newbie
timestamp: January 19, 2014, 05:30:54 pm
content: nctnico, thank you for replying, but:1. I am not expecting the diagnostic menu to solve the problem magically by its own, but to get some hints for further investigation steps. This is the reason I ask for more details of the diagnostic menu.2. I do not think the power supply is the root cause for the trigger problem since the voltages are ok and the line sync output of the supply is working correctly (I recognised another effect: switching the scope on - no screen, no beep - and then switching the external fan on - refer to the picture "bench": here you see where it is positioned - this cares for an immediate start of the scope. It seems some inductive coupling makes it to start: repeating the fan switch-on with a started scope creates a short interference on the CRT).3. In self test all remaining steps are passed. This covers more sensible tests as input channel gain setting, offset gain, ...I do not deny that I have 2 problems with the scope, but I am convinced these are independent to each other.I would appreciate to receive assistance from a LeCroy specialist - thank you.

author: Dtec
author_rank: Contributor
timestamp: March 07, 2017, 03:36:01 am
content: Should listen when asking for advice ripple causes all kind of errors with a normal voltage reading own same scope had same problem esr on one cap very highSent from my iPhone using Tapatalk

author: snoopy
author_rank: Frequent Contributor
timestamp: March 07, 2017, 11:30:59 am
content: I believe this dude had a problem in the power supply on a Lecroy Scope