Author Topic: LeCroy 454 Repair  (Read 1737 times)

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Offline vaualbus

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LeCroy 454 Repair
« on: January 23, 2016, 07:36:17 pm »
I all, so after I find the schematics and the service manual, I begin to troubleshooting the unit. I find a bad mosfet the 2sk3148 and I replaced it with the irf540. Unfortunally that is not the problem.

Here the situation:
If I connect the unit width the 220V both fuses breaks, so something is bad on the primary side or on the pfc board.
 Than I come out with the idea of power the unit with the external dc in, so I bought a 19V 5A psu and connect it to both CN9 and CN10. (The stand by voltage is generated from the main ac so without it I never get the stand by voltage).
And than the problem start:
   - If I connect all the cable to the analog board and to the motherboard, the unit turn on for a while and than turn off.
   - If I only connect the motherboard I can't get the motherboard to start But the motherboard is good, I try it with an external psu, and it boot.
   - If I connect only the analog board the psu automaticly turn on and all the voltages are ok.
   - If I mesaure the -12v rail when all the cable are disconnected it measure only -3.5v, but it become ok when I connect the analog board to the power supply.

Now I'm wondering what can be wrong in psu? Any ideas?
Also anyone have an idea where to find the restore program because the unit miss the hard disk so I need to insert a new one and reinstall all the software.
In the service manual it is rittent that you need the "WS400 Series Control Program" cd/dvd, and the "Startup Disk for WS400 Series Control Program" floppy disk.
Where to find an image of it?
Best regards, Alberto.

Offline JacobPilsen

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Re: LeCroy 454 Repair
« Reply #1 on: January 23, 2016, 08:31:46 pm »

Offline vaualbus

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Re: LeCroy 454 Repair
« Reply #2 on: January 23, 2016, 10:30:57 pm »
So I take a look at the Pfc board and found a bad mosfet and bad diode.
Anyway that not solve the issue I'm looking.
I really think that there has to be a problem on the -12v rail. Is so strange that is only -3.7V unloaded and go to -12v when all the board are connected.

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