Lecroy 7200A Teardown and Repair... Repaired! (mostly)

[JPortici]

Hello folks,
for those who don't know.. Hi, my name is Jack, i design electronics, write firmware and occasionally write software for PC...
And I am a Test Equipment Addict.

Today I received this big baby, a LeCroy 7200A marked as not working...
It was only 150 britbucks shipped! I couldn't possibly leave it there withoud bids, could I?
Also because it included a
Anyway, the seller said that the scope developed a fault about 10 years ago and it was put away ever since.

Unfortunately, while a service manual for the plugins can be found, the service manual for the mainframe is only available at the Unobtown public library. Lecroy doesn't seem to have it anymore.

Anyway, from my sources the mainframe is actually a PC running an old version of DOS and some custom driver to interface with the plugins, which are self contained data acquisition units.. The mainframe displays the data, saves waverform, does FFT, networking etc.

Let's Begin!

Photo album: https://flic.kr/s/aHskXDAkRk

First of all, I couldn't believe it when they told me it was bigger than a tek mainframe.

I proceeded Removing the top, the back and then the rest of the screws holding the power supply together.
Then, the power supply slides back and after disconnecting the power connectors it can be removed.

Opening the power supply reveals that there are two boards, one i think it's for a mains preregulator and the second one that regulates all the power rails.

Each connector has its own set of common pins, however it appears that each connector is isolated (Common pins between connectors are not tied together)

I didn't notice anything suspicious so i put it back together, connected and threw the switch, without inserting the plugins.

BEEP.
VERY loud fans spinning.
Green glow from CRT, but no image.

Suggestions?

PIC: Scope Tower

[JPortici]

Meanwhile, I have already punched myself down there several times.

I KNEW I shouldn't have thrown away that floppy disk i found the other week (and yet i have many sony disks for amstrad CPC computers)
I KNEW I shouldn't have thrown away that ancient mechanical keyboard that had the big old style din connector but i should still have kept the big din -> ps2 adapter from another ancient computer

bottom line: never throw away anithing. HOARD.

[JPortici]

I removed the left panel to play around with the CRT controls (located behind the panel)

To my surprise the video card was removed from its socket. I put it back but no luck, still no video signal.



I wonder if i should probe the D-Sub connector for activity?
I'm not sure if the board is booting, at all.
I hear the beep so hardware self test shoud have passed but i don't see any activity on the floppy disk LED - even though i haven't put in a disk i remembr the light coming on and off at boot on my old computers - nor i can hear the hard disk head moving

[JPortici]

Well you know how these things go...

so, while i'm waiting for new memory sticks i find an old floppy disk.
I insert it inside the slot and WTF?

Crt becomes blue???

i give the scope a couple of hits and to my surprise the splash screen.

"Lecroy"

self test passed

scope is working.

I repeat, scope is working. Unbeliveable just like those old PCs, they need a beating once in a while.

Anyway, i see a lot of encoders that needs a good clean, and both the plugins run self calibration every few minutes.. i don't think it's correct, i'll dig in the manuals...

[nctnico]

Hello Jack!

That self calibration is probably normal. The interval probably gets longer once they are reaching operating temperature.

[JPortici]

During self cal it changes the amplitude scale so i'm not sure it's ok,
no worries as i have the op and service manuals. I played with it for like 5 minutes, then i had to left for vacation...
So it's a problem for tuesday-me

[JPortici]

LeCroy 7200A Repair

In this episode, I go on with tearing down the front panel and fixing those encoder that really needed some cleaning.

Is there something i can do for the optical encoders? One is missing steps. Or at least, i suppose those are optical. No clicks, 6 pins instead of 3


optical encoders


1kHz probe compensation signal generator

I already reassembled the front panel but one of the optical encoders is still wacky, i don't really know if i can fix it or i have to substitute it, period...

ps: to put this back on the front panel assembly was a real bitch

Next step will be actually fixing the CRT cable/assembly so i don't get BSOD again (not really BSOD... but screen becomes blue and scope doesn't start anymore until i hit it again on the side)

[Jonathan9192]

Hey,

sorry for bringing this up again, but may I ask wether you made any further progress on this project?
I am considering to buy one of these scopes as well and found this website quite informative:
http://www.ccltd.com/LeCroy7200A/

Maybe it is of help for you as well...

Cheers,
 Jonathan