Hi everyone,

I'm new here but I'm an old LTZ1000 user. I'd just like to reply John's mail
on Fri Aug 26 18:27:20 UTC 2011:

---------------------------- I quote --------------------------

Does anyone know if the ebay / Chinese LTZ1000 are the real thing?

E.g. 250823975393.

---------------------------- Quote end--------------------------

In short answer, they are definitely NOT REAL.

I personally have many experiences in buying LTZ1000ACH/LTZ1000CH, part for
my own use part as group buys for other Chinese volt-nuts. Here is the list
of type of LTZ1000 one can buy in China:

1.  Brand new from authorize dealer 
   

http://www.zmdz.com/bbs/incomefiles/20118/27161230351.JPG

http://www.zmdz.com/bbs/incomefiles/20118/2715363179144.JPG

Expensive but true.

2.  Used
   

http://www.zmdz.com/bbs/incomefiles/20118/271643256989.JPG

http://www.zmdz.com/bbs/incomefiles/20118/27163828901.JPG

Original marking and short legged as dismantled from used board, cheap and
pre-aged, these are the best.

3.  Legs extended or/and re-marked
   

http://www.zmdz.com/bbs/incomefiles/20118/2715505128556.JPG

http://www.zmdz.com/bbs/incomefiles/20118/2715471520943.JPG

http://www.zmdz.com/bbs/incomefiles/20118/2715425289325.JPG

There are many skilled workers in China who can make the extension, not only
for LTZ1k but for other IC as well. As it involves high temperature heating
while joining, it may have permanent effect on long term stability, if not
damaged. Therefore, these are not recommended even though they are genuine.

4.  Faked
   

http://www.zmdz.com/bbs/incomefiles/20118/2715534949602.JPG

http://www.zmdz.com/bbs/incomefiles/20118/271554111419.JPG

http://www.zmdz.com/bbs/incomefiles/20118/2715533647158.JPG

These are NOT LTZ1000 at all. The original IC must be some cheap op-amp and
later re-marked plus legs extended. I once bought 30 of those and have they
refunded afterwards.

Lymex Zhang

Dear All,

Not sure where else to ask this question - I am hoping that a fellow
volt-nut has experience with the 3468A.

I have an EBay special, known bad when I got it, HP3468A.  When powered
on it simply cycles through what looks like a test (all / most elements
of the lcd display turn on) and an Overload indication.

I have followed the repair manual as far as I can, but since the unit
never stabilizes - the processor is continually interrupted and the
cycle repeats - I have not really found anything.

The 3468A uses a 3 volt battery backed up RAM.  The 3 volt lithium cell
reads ~ 1.5 volts so clearly the RAM contents are gone.

Could there be something in the RAM that when not present forces the
processor to reset?

If it is possible that the missing RAM information is causing the
continuous run / rest cycle, any idea how I could I restore the RAM
contents?

Thanks for any pointers!

Best regards,

Bob Smither, Ph.D.                                smither@c-c-i.com

---==
The Three Great Lies:

1. Your check is in the mail.
2. I'll respect you in the morning.
3. We're from the government and we are here to help you.

---==

Neil's suggestion (to check the power supplies) is a good one.

Make sure the +5V, -15V and +15V rails are correct - and use an oscilloscope
to check for excessive ripple.

You didn't mention if you have the rechargable battery option (opt. 001),
but if so, that adds to the number of possible problems.

I definitely would replace the 3 volt lithium cell (BT551) ASAP.

Also make sure that the front panel "Reset" button isn't stuck in the
pushed-in position.

If you're lucky, doing all the above will lead to a cure. If not, then it
sounds like some other fault is still causing the "RESET" line (at U501) to
keep cycling. It doesn't sound like you're getting through the turn-on
self-tests far enough to see possible further error codes (e.g., Calibration
RAM error, or RAM error, or ROM error, or A/D converter error).

Let us know how you come-out on it.

Cheers!
Greg

----- Original Message -----
From: "Bob Smither" smither@c-c-i.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Saturday, August 27, 2011 9:48 PM
Subject: [volt-nuts] HP3468A

Dear All,

Not sure where else to ask this question - I am hoping that a fellow
volt-nut has experience with the 3468A.

I have an EBay special, known bad when I got it, HP3468A.  When powered
on it simply cycles through what looks like a test (all / most elements
of the lcd display turn on) and an Overload indication.

I have followed the repair manual as far as I can, but since the unit
never stabilizes - the processor is continually interrupted and the
cycle repeats - I have not really found anything.

The 3468A uses a 3 volt battery backed up RAM.  The 3 volt lithium cell
reads ~ 1.5 volts so clearly the RAM contents are gone.

Could there be something in the RAM that when not present forces the
processor to reset?

If it is possible that the missing RAM information is causing the
continuous run / rest cycle, any idea how I could I restore the RAM
contents?

Thanks for any pointers!

Best regards,

Bob Smither, Ph.D.                                smither@c-c-i.com

---==
The Three Great Lies:

1. Your check is in the mail.
2. I'll respect you in the morning.
3. We're from the government and we are here to help you.

---==

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