Electronics > Repair

Lecroy Waverunner 64Xi-A no power

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analogRF:
My newly arrived 64Xi-A (black case, red acq board, Win7 32bit) does not power on. The power button works (turning on and off) and fans work but that's it
Blank screen with no beep or any sign of life other than the fans.
I confirmed that the motherboard alone boots normally into windows 7 with external ATX power supply and still with the scope's LCD/front panel (no need for VGA monitor). The CMOS battery is new and no issue there.
I want to power up the damn PSU alone with the motherboard and no acq board but I dont know how.
The regular PS_ON (green wire) on ATX connector does not power up the PSU

Does anybody know how to power up the PSU and motherboard without the acq board?

analogRF:
I have traced back the power on key from acq board to the cpu board power on key. so it's wired like a regular PC
but it seems not to be enough to turn on this thing
I think there might be some sense lines that the PSU needs to check and if it doesn't see them it wont power on...
who knows where the sense lines are if that's the case

at the moment the only way to power it on is to have all the 3 connectors connected to the acq board
then it powers on but with blank screen and fans spinning no sign of life

there is no access to the ATX connector on the cpu board in this state but on the acq board it seems all voltages are ON except the important +3.3V (+/-12,+5,-3.3 are present) so I guess that is the problem although I dont know how this could prevent the motherboard from coming on but I dont have access to the ATX connector so maybe something is also missing there

anybody has any clue?

analogRF:
the +3.3v missing on the acq board is indeed the same that also goes to the PC motherboard so that explains why the PC does not boot

now the question is what has happened to the 3.3V.
any previous experience?

this PSU is mad complex with soldered on daughter boards all over the place for each rail....

I asssume the primary side and switching must be ok because all other rails are present except this one
which measured 0.3V on the acq board. can it be the output caps? physically they look ok.
I hope it is not something on the daughter board

the problem is I cannot power it on to work on it. so I am blind...

tooki:
At work, we've seen a lot of WaveRunners fail with power supply failure. Basically, nearly every one we have that's more than about 5 years old has failed. (My colleague has fixed something like 5 or 6 of them by now!!)

The problem has been the standby power supply caps failing, and without the standby supply, the rest of the power supply can't start up.

I don't know if your model failed the same way (it kinda sounds like a different failure mode), but if the root cause is the same -- cheap electrolytic caps* -- then maybe this gives you a place to start looking.


* I told our LeCroy rep that I think it's indefensible that they use cheap caps in instruments of this price class, and that this is something that will play into future scope purchases. At these prices, I expect only top-brand capacitors. It's not as though we are talking about more than a few dollars price difference.

analogRF:
standby is not an issue here and all the rails come up except the +3.3V
the big elec caps are all Nichicon but still I suspect my problem could be a bad cap.

i just wish there was a way to power up the PSU alone to do work

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