Lecroy WS422 strange behaviour

[Martin72]

Hi,

This scope we don´t want to repair because only for having a first look on it, lecroy want to have more than 2 sds2104x+ will cost together..
But I take a look...
So what´s wrong ?
First it seems nothing, you can power it on ( looooong boot time...) and it´s doing what you expect it should do.
But sometimes or better more and more, after booting one or both channels are "freaking out".
The "noise" are filling the whole screen then, regardless of the voltage/div or if you switch to GND.
I´ve got a feeling this is more than simple contact problems because:
Example from a hour ago, Ch1 is noisy as described so I swithed it off, turn ch2 on.
It shows a distorted waveform(bodnar connected) which becomes clear when you switch the "noisy" ch1 on...
But in this scenario scope won´t do measures, the values are randomly.
So....
Turn it off.
Then on again and if you have luck, everything is fine....
This would be an interesting project to find out what´s going on, I´ll report it here step by step.
But if anyone here got the same issue before or knows from it, tell it here....
Want to fix it, it´s a nice scope to have together with my 12-bit.
But as I said above, this sounds not easy...But that would be a little bit boring when not. 

Martin

[tautech]

Older scope might need recapping so KISS and first check PSU rails for ripple then any on-board converters too.

[nctnico]

Checking the PSU for capacitors with bulges and smelling like cat wee is a first good step. A second step is to reseat all boards and connectors. This could be a contact problem somewere.

[Martin72]

Yepp, you´re both right.
Concerning contacts, as this scope were often worldwide on travel for service, the "graphic card" was often loosen it´s contact, so one of my first tasks at work as a beginner here (2005) was to fix the card with a self build holder...
Took the scope apart a few hours ago, waste amount of dust in it, fans are loudly, CPU cooler is dusty...
I´ll make a total cleaning up, then looking further, visible quality control...
The building quality is remarkable good, no wonder because it´s from iwatsu.
Looks like a small PC with some additional parts...

[Martin72]

This is building quality...
Maybe I got a little bit time today to tear it down further, let´s see.

[nctnico]

If the build quality of a piece of Lecroy branded equipment is high, then it is a rebrand. 

[Martin72]

Shoot ! 

[egonotto]

Hello,

have you the service manual?

Best regards
egonotto

[tv84]

Hello,

have you the service manual?

Best regards
egonotto

Here.

[Martin72]

Now I got it ! 

[coromonadalix]

before going too far  i would make  asap  a drive backup  just in case .....

[Martin72]

The service manual is very informative, every SM should be in this way...
Wish I would have my holidays now...  

[darkstar49]

In fact, I'm even surprised they provided no schematics in the SM, as opposed to the one for the (non -A) WR6K...?
Or is this a crippled version ? Or linked to some Iwatsu copyrights ?

[Martin72]

before going too far  i would make  asap  a drive backup  just in case .....

I´m thinking about to use a usb stick for it, this should be OK or ?

[RedCali]

before going too far  i would make  asap  a drive backup  just in case .....

I´m thinking about to use a usb stick for it, this should be OK or ?

The most important thing to have a Backup is the calibration data - stored  unter D: in a hidden folder, cause if that get lost you have to send it to lecroy and thats quite expensive....

You can as well make a raw copy off the drive: http://www.runtime.org/driveimage-xml.htm

No matter where to stored - just be sure you have it :-)