On Mon, 10 Sep 2007 00:58:31 -0700 "
wrote in Message id:
. com:

[Sorry for the repost, but I just noticed that sci.electronics.repair
is not in the groupline - I've taken the liberty of adding it.]

We got some problems with HP/Agilent 4194A Impedance/gain-phase
analyzer.

It get stuck when the equipment starts up.
The error message shows "CPU_A RAM R/W error. 40000H".

Please advice us how to fix the problem. Is there any third party
repairing these instrument? We have called Agilent, it is sad to know
that they have stopped support for this instrument since 2005.

kristo

I work as a tech for a company that salvages and repairs test equipment:
https://www.techrecovery.com/
We don't normally do repairs for third parties, though...

We have called Agilent, it is sad to know
that they have stopped support for this instrument since 2005.

I haven't worked on this particular piece of equipment (yet) but start
with the service manual:
http://www.home.agilent.com/agilent/...2489.536879058
If that link doesn't work go here and navigate to the manuals section:
http://www.home.agilent.com/agilent/...eng&cmpid=4533

This would be a tough one, as the schematic of the A6 and A7 boards is
unreadable (Why did they even bother?) There appears to be two banks of
DRAM on each board, each bank is 256KB. Given this, it appears that the
upper bank of memory is defective on either the A6 or A7 board. Start by
probing the WE, RAS and CAS lines on each bank of A6 and A7. If they
appear OK, look at each DRAM's data line for a bit that may appear to be
tied or faulty. If you had a signature analyzer, that would be a plus!