Hello Dave,
As an introduction, I am the moderator and owner of the independent LeCroy_Owners_Group on Yahoo! Groups. You can find a lot of information on the group site as well as overflow manual and firmware files,etc. on
www.ko4bb.com in the LeCroy Manuals section.
I can tell that you like poking fun at the circuitry and design as you go through things but remember in 1999 no manufacturer had an equal to these scopes in terms of sample rate, memory depth and math measurement capabilities. If you add in all of the possible options the deep memory (2Mpt/channel simultaneous 1Gs) version of this scope went for something like 40K, maybe more. I have several LeCroy scopes from this era that I still use on a regular basis and a more modern 104MXi that I use almost daily.
It took years for HP and Agilent to finally begin to understand that deep memory is important in a digital scope, and in some cases I still don't think they get it. And how you manage that memory is even more important. LeCroy currently makes some of the real "killer" scopes on the market today. Their new 12bit one is a must see.
Maybe you should contact your local LeCroy office and see if they would agree to have you review one of the more modern ones. The math and performance is outstanding. I think their fastest scope is 45GHz at 100+GHz sample rate!
To address some things in your video.
Originally this series of scopes was manufactured in the LeCroy plant in Switzerland (93XX and 93XXA). The C model was manufactured in Chestnut Ridge NY as all of the high line series (making LeCroy the only remaining U.S. manufacturer of oscilloscopes.
These scopes were never really intended to be serviced in the field like a Tek 475A. The units were calibrated and verified by specialized calibration and troubleshooting equipment developed by LeCroy. This is not to say that you can't fix the scope, indeed I have repaired many but there are certain things that make the repair difficult.
For one thing there are many, as you have noted, custom IC's that LeCroy designed that are simply not available on the open market or from LeCroy since the units are long out of production. Specifications for the parts are also unobtainium. As you also noted there are many GALS in the scope that are of course protected so replacing those would be difficult as well. I would recommend finding a similar one one ebay for spare parts.
One particular problem with the 9384A/C is that the input in the 50 ohm mode is susceptible to ESD damage from a charged 50 ohm cable. This is a common fault. The HEF series part was a custom and the only fix is to find another scope that you can use for parts. I currently have a 93X4C scope that I junked because it had three wrecked inputs.
As for your scope problem since it is common to all channels I would suspect a data bus problem, maybe even system ram. There are 72pin SIMMS on the CPU3 MC68EC030 card that you can swap to see if the problem goes away but I don't think the ADC cal errors are caused by that but swapping them is easy. There is a note that I wrote up on the group site about the memory. Maybe just reseating the CPU card may work as these get jostled in shipping.
As an aid to trouble shooting there is a maintenance mode that you can enter from the from panel with the scope stopped. See the attached excel file for hints.
Also don't forget that we have a fairly large base of users on the group so feel free to join and post your problems there. Many of the group members have experience fixing these scopes.
While you have the unit apart I would also recommend that you measure and scope the power supplies.
I believe that the Coax you see is for distributing timing to various places so that the sampling is truly synchronous. One of the features if these scope is the ability to combine 2+2 channels to double the sampling rate and the memory depth. By using an external PP adapter you can double that again (but you are restricted to 50 ohm measurements with the adapter).
Fortunately I have not had to work on the main acquisition board on these scopes except to fix an input relay (sometime a rap with a pencil will un-stick them) or
to make a rare calibration adjustment. If these scopes are not abused they will hole their calibration for years. Usually all that is needed is to occasionally blow out the dust and every 5 years or so replace the rechargeable lithium battery on the CPU card. There is a note on the site on the battery replacement as well.
Take care and good luck and let me know how you make out.
Sam Reaves
(Scopeman)
P.S. I do not work for LeCroy or have any official affiliation, I just like their stuff!
P.P.S - The real LeCroy scopes are the ones that are above the entry level WaveAce and WaveJet models.
P.P.P.S -- You need to add rar as one your acceptable file upload types!
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