Products > Test Equipment
LeCroy LW420 Arbitrary Generator
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wishboneash:
I have a LW420 that has a dead display too. The -12V supply is shorted out. I see 0.5 ohm to ground. I can hear the HDD doing something and the two signal outputs are red. Hoping that the main part of the AWG is OK. I measured over 3Mohm on the -12V supply on the board after disconnecting the power supply connector from the PS unit. The +12V, +5V and +15V supplies look good. Will have to get into the power supply unit and do some investigation. Thanks.
wishboneash:
I found out that the second switched mode power supply has failed completely so all the negative voltage power supplies are dead (-5V, -12 and I believe a -2V supply). I externally provided the -5V and -12V supplies and I got the unit to power on but I got a message on the screen saying it needs the firmware installed (from floppy). Is there anyone in internet land who has such a floppy? Thanks.
shakalnokturn:
You'll have to subscribe to the group to download.
The file there that seems small enough to fit a floppy is one I uploaded at the time I had a LW420, can't remember where I got the file from then... I never got the LW420 working anyway.
There are also HDD images available which may turn out simpler than getting a working FDD and floppy combo.

https://groups.io/g/LeCroyOwnersGroup/files/Old%20firmwares%20archive/LW420/Lecroylw420-311.IMA

https://groups.io/g/LeCroyOwnersGroup/files/LW420%28A%29
Kryten 2X4B:
In my post from 2015 I mentioned that the rectifier diode for the -12V supply was shorted, that caused all the negative rails to fail. Apart from the diode, I had to change the controller chip, the reference, the primary side MOSFETS, and some resistors including the one for current sensing. Without the negative supplies running you will hear the HDD trying to boot but there will be nothing on the display as the video is disabled prior to the LeCroy logo being displayed and the video passes through some MAX442s which run on +/-5V rails so without -5V the display will remain blank.

The HDD in mine failed before I had imaged the HDD, the plan was to use a CF card. Since then I got a disk image and the LW420 is running with a CF card and passes the self-test.
wishboneash:
I got mine to work after working on the power -ve SMPS. Turned out to be a failed rectifier on the -12V supply along with a blown MOSFET on the output side. I added some protection for the rectifier by adding a bypass capacitor for switching transients. Perhaps the diode was not rated correctly for reverse breakdown when the inductor switched off. With some help on the LeCroy IO group, I got an HDD image which I put onto a SD card and now it boots up perfectly. It's a nice AWG and there seem to be many around with the failed HDD which can be easily converted to a CF or SD card drive.
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