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WaveSurfer 44MXs-B
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Hi All,
My first post on here, but I have been a long-time advocate of LeCroy scopes. A while ago, I inherited a WaveSurfer 44MXs-B which I think is a fantastic scope. Probably one of the best ever made by LeCroy. Last week it stopped working completely. When you switch it on, the fans start and stay on, the screen glows, but there are no other signs of life (no beep, no illumination of the controls lights). The scope will then not power down using the front panel switch and it has to be turned off at the mains. Before I start tearing the unit apart, does anybody have any suggestions with regards to this fault on this fairly modern model? Thank you all very much for your time. I anticipate that I will be spending more time on here soon!! |
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first of all, it’s a PC... so if you don’t see anything on screen, this might be due to either the motherboard or the power supply... in either cases not something you’ll find a replacement for at the store...
while the motherboard has a standard mini-ITX format, it has a PC/104+ connector, you’re not likely to find one like that... you won’t get around tearing it apart... be careful to mark all the screws and make lots of pictures to sort it out afterwards.... ;-) |
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huynh@dm4lx.de
Hello,
my suggestion is to test the mainboad separate by powering it from a standard ATX power supply. Unfortunately, you have to remove the acquisition board with care. There are several Torx screws holding the acquisition board and the perpendicular input front end board in place – including several screws all around the metalwork.
The mainboard has an ordinary 20 pin ATX (Molex) connector, but a 24 pin connector on the power supply side works as well.
Use an external monitor to see if the mainboard does boot into POST/BIOS. The front panel header is extended via a twisted pair cable (red and black) going tot he acquisition board. To power the mainboard on, you have to short these two pins together – same like the front panel switch of a desktop computer.
I attached some photos of the teardown of my unit (WS 44Xs-A). The –B version should be similar.
Regards,
Kevin Huynh_._,_._,_ 
acq board screws.jpg
front panel connectors.jpg
mainboard with pc104 card.jpg
pc104 card 2.jpg
acq board lecroy bus disassembly procedure.jpg
acq board lecroy bus.jpg
acq board overview.jpg
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Hi All,
I have handed this scope over to a friend who is working on it when time allows. He has stripped it down as recommended by Kevin above. The main board does go into POST when attached to an external PSU. This is as far as he has got at the moment. He has asked me if I can get hold of a service manual for the WS MXs-B. Does anybody out there have one? Many thanks. |
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There's absolutely no chance you'll get one, as this model is still being sold by Lecroy... (unless you've got a family member working at Lecroy ... ;-)
Honestly, from my personal experience, the PSU is the weak part in ALL scopes with that form factor from Lecroy... I'd get in touch with Lecroy, and check whether they'd agree to sell you one of those (should be less than 500 USD), unless you're willing to fix yours, but that can be a long and painful process... There's an interaction between the acq board and the PSU for powering on the different components of the scope (the mainboard being the last one...), so in theory, it's not impossible that some components are stuck (as well ?) on the acq board, but I'd put this possibility aside before any potential issue with the PSU has been excluded... Good luck ! |
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Kevin Huynh
Maybe you should check voltages…
I did a quick measure on my unit, when I did a teardown two months ago. Unfortunately, the power supply seems to have some protection against operation with no load or with open sense wires, so I did not managed to start the power supply without any connected boards.
The power supply pinouts in the provided PDF is just quick and dirty, some signals are just guessed. I didn’t want to risk my intact power supply by shorting sense/signal wires in a random manner to force a startup without load.
Freundliche Grüße / Kind regards
Kevin Huynh
Von: LeCroyOwnersGroup@groups.io [mailto:LeCroyOwnersGroup@groups.io]
Im Auftrag von Philippe Annet
There's absolutely no chance you'll get one, as this model is still being sold by Lecroy... (unless you've got a family member working at Lecroy ... ;-) |
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Hi,
I also have 44MXs-B with a similar problem. Behaves equally in both of these setups: scope + VGA display vs motherboard + external ATX PSU + VGA display It wasn't used for a while and when powered it was restarting constantly. DDR2 stick was replaced. After that restarting stopped but it still won't boot. There is nothing on scope screen nor external VGA monitor (both are black and empty all the time). Scope stays powered on, with FANs spinning fast, there is no BEEP sound, one red LED inside the scope is on. Hard drive is checked and is OK. Motherboard battery measures 3V, but I guess it is quite old. Should it be replaced anyway? Is there anything else that should be checked? Happy holidays! |
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Hello,
I just uploaded a service manual for the Xi-A, which should be similar to this scope. No schematics but it does have pinouts. The power supply has sense lines, so you won't be able to measure voltages with the power supply disconnected. Since your fans turn on, thats a good sign, you should be able to measure all the voltages in that state. |
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Hello My first post here. I had a similar issue with a dead display on a LeCroy LW420 AWG. I am trying to bring it back to life and going through the troubleshooting procedure I found that one of the SMPS power supplies that generates all the negative voltages (-12V, -5V and -2V) was dead. Both the switching FETs on the HV side were blown and one of the rectifiers on the 12V rail on the secondary side of the transfer was shorted out. This pretty much killed the display on the machine. Powering it externally with the -12V and -5V brought the display alive. I have other issues which I can describe in a different thread. Hopefully this gives some clues about your unit. First thing to check would be all the power supplies. |
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Thanks for the manual, it is somewhat similar. Measured the voltages and they seem OK (+/-12, +5V, -6V, +/-3V).
Restarting loop actually came back, don't know the exact reason but it is more likely to go into restarting loop with VGA connected. So the DDR2 replacement has no effect. While I was at it, also replaced the old CR2032 (which measured 3V) with a brand new one (measures 3.3V) but it also doesn't make a difference. All 4 FANs are spinning but the TACH signal on the one for ATX PSU is stuck at 50mV, compared to others and it doesn't seem to be a FAN problem. It is 50mV without the FAN as well + it has a 3.3V pull-up resistor on that pin which should pull-it up to 3.3V, but it doesn't. Resistor receives 3.3V, measured. Is this signal something that will stop it from booting? How to track this signal on the board, where does this signal go? Regards |
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Some more details:
Viewed the TACH pin (without the FAN). At power up, it goes HIGH to 3.3V for about 330ms. After that it goes LOW and stays LOW. Restarting loop occurs every 12s. @ Philippe Annet: PCB that connects motherboard to the acquisition board is RED, goes into PCI slot, has 2 ETH and 1 SATA connector on it. |