Electronics

Guest · Posted: Mon Mar 28, 2005 10:10 pm Post subject: Lecroy 9400

Hi
After 3 years my Lecroy 9400 has died. It no longer responds to the
front panel or GPIB. Everything still works but the settings are stuck
and can`t be changed. There is a red LED glowing on the main board
which I guess is a fault indication. My gut reaction is that a clock
has stopped oscillating but where to start???

Any help appreciated.

kishikawa · Guest

Hellow Nick,

I have Lecroy 9450A having some trouble.
But most of time it works properly.

There is a red LED on front panel interface board(main board?).
Red LED is glowing,it blinks when changing front panel settings.
Maybe LED glowing means not fault.

I guess clock is not setted properly maybe PLL circuit is in problem.
So cpu is waiting until clock setted signal.

If you have another Oscilloscope.
Check clock out signals in rear panel.
My Oscilloscope does not output any signals when troubled.
But when Oscilloscope works well there are clock out signals.

Your trouble is very similar to my trouble.
Most of my trouble is not triggered.
But rarely I can not change front panel setting as your trouble.

I am shooting this trouble.
But I have not schematic diagrams,service manuals.
Have you any advice?

Thank you Kishikawa

<nick.kenworthy@ntlworld.com> wrote in message
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Guest · Posted: Wed Mar 30, 2005 1:10 pm Post subject: Re: Lecroy 9400

Many thanks for the response.
I see what you`re getting at. Where are you looking for signals on the
rear panel?? At one of the RS ports or the GPIB??
Had a poke around with another scope and find that both crystals are
operating....although did `nt know there were PLLs on board.

Thanks for the tip on that LED....I`m certain it does n`t
blink....maybe confirmation that front panel signals are not getting
through.

A schematic is the answer I think.

Nick

kishikawa wrote:

kishikawa · Guest

Hi Nick,

Sorry I have not Lecroy 9400.
Lecroy 9450A has clock out one of 4 BNC connector in rear panel.
I think 9400 has clock out too, Sorry.

My 9450A has clock-out-connector marked J6 in trigger-board.

I am looking for PLL too.
I think it must be near 100MHz crystal osc circuit.
I have not schematic.I check IC name and pin-layout and pcb circuits.

kishikawa · Guest

Hi Nick.

I maybe fixed LeCroy 9450A Oscilloscope intermittent problems.

1.100MHz Xtal is poor ----> change to 100MHz Xtal OSC.

2.ECL power supply is -3.6V ----> correct to -5.0V.
Most of time it supply -5.0V.
I found it drop to -3.6V when LeCroy 9450A is not work fine.
Variable resister for voltage adjustment in power supply unit is bad.

Nick Check power supply voltages.
-15V,+15V,-5V,+5V is correct or not .

Thank you Kishikawa

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