[volt-nuts] LTZ1000ACH and LTZ1000CH in China

[LMZ]

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

Loading Image...

Loading Image...

Expensive but true.



2. Used

Loading Image...

Loading Image...

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

Loading Image...

Loading Image...

Loading Image...

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

Loading Image...

Loading Image...

Loading Image...

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

[Charles P. Steinmetz]

Post by LMZ
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.

I've heard horror stories (some on this list) about how components
are removed from boards -- putting the boards in a wood fire or
holding the board up to a gas burner, then whacking the board on
something so the parts fly off. If the reports are true (and I have
no way of knowing, but the photos in the links above certainly do not
give the impression that the parts were removed carefully with proper
desoldering equipment), I'm not sure I'd trust the used parts to be
in pristine condition any more.

Best regards,

Charles

[LMZ]

Dear Charles,
I believe those horror stories are true. However, metal ICs removed that way
looks bad and can only be used for re-marking purposes. When buying used
LTZ1k, I always ask seller for real photo first. Here is an example:
Loading Image...
Lymex Zhang

I've heard horror stories (some on this list) about how components are

removed from boards -- putting the boards in a wood fire or holding the
board up to a gas burner, then whacking the board on something so the parts
fly off. If the reports are true (and I have no way of knowing, but the
photos in the links above certainly do not give the impression that the
parts were removed carefully with proper desoldering equipment), I'm not
sure I'd trust the used parts to be in pristine condition any more.

Best regards,
Charles

[Rob Klein]

Post by LMZ
Hi everyone,
I'm new here but I'm an old LTZ1000 user.

Well, if you are, as I expect, *the* Lymex of
http://www.eefocus.com/lymexbg2vo/blog/ (among others),
then your reputation definitely precedes you on this list and I for one
would like to extend a warm welcome
to you.


Best regards,
Rob Klein.

[David C. Partridge]

Rob, Is there an English version of that blog?

D.
----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On Behalf Of Rob Klein
Sent: 27 August 2011 12:47
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] LTZ1000ACH and LTZ1000CH in China

Post by LMZ
Hi everyone,
I'm new here but I'm an old LTZ1000 user.

Well, if you are, as I expect, *the* Lymex of http://www.eefocus.com/lymexbg2vo/blog/ (among others), then your reputation definitely precedes you on this list and I for one would like to extend a warm welcome to you.

[Rob Klein]

Post by David C. Partridge
Rob, Is there an English version of that blog?
D.

Not that I know of, but it translates reasonably well.
http://translate.google.nl/translate?hl=nl&sl=zh-CN&tl=en&u=http://www.eefocus.com/lymexbg2vo/blog
<http://translate.google.nl/translate?hl=nl&sl=zh-CN&tl=en&u=http://www.eefocus.com/lymexbg2vo/blog>

Rob.

[Bob Smither]

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 at 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.
====================================================================
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smither.vcf
Type: text/x-vcard
Size: 140 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110827/a6a9e465/attachment.vcf>

[Neil Gruending]

Bad power supply?

Post by Bob Smither
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 at c-c-i.com
====================================================================
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.
====================================================================
_______________________________________________
volt-nuts mailing list -- volt-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[Bob Smither]

Post by Neil Gruending
Bad power supply?

Thanks for the reply. One of the first things I checked was the power
supply levels - all are correct.
--
Bob Smither, PhD Circuit Concepts, Inc.
=========================================================================
Blessed is he who expects no gratitude, for he shall not be disappointed.
-- W. C. Bennett
=========================================================================
Smither at C-C-I.Com http://www.C-C-I.Com 281-331-2744(office) -4616(fax)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smither.vcf
Type: text/x-vcard
Size: 140 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110828/785f93dc/attachment.vcf>

[gbusg]

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 at c-c-i.com>
To: "Discussion of precise voltage measurement" <volt-nuts at 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 at 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.
====================================================================



--------------------------------------------------------------------------------


_______________________________________________
volt-nuts mailing list -- volt-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[Bob Smither]

Post by gbusg
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.

Done. All the supply rails look good.

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

The unit does not have that option.

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

I did this, but no change. I wonder if the boot process is assuming
something that has been lost from the RAM.

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

Reset button? Don't see that.

Post by gbusg
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).

Agreed.

Post by gbusg
Let us know how you come-out on it.

Will do.

Thanks for the feedback!
--
Bob Smither, PhD Circuit Concepts, Inc.
=========================================================================
Blessed is he who expects no gratitude, for he shall not be disappointed.
-- W. C. Bennett
=========================================================================
Smither at C-C-I.Com http://www.C-C-I.Com 281-331-2744(office) -4616(fax)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smither.vcf
Type: text/x-vcard
Size: 140 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110828/01af76bf/attachment.vcf>

[gbusg]

Post by Bob Smither
Reset button? Don't see that.

The Reset function can be invoked by hitting "blue" (keyshift) key +
SGL/TRIG (TEST/RESET). (This might be only labeled "TEST" in blue on some
versions.)

Post by Bob Smither
I did this, but no change. I wonder if the boot process is assuming
something that has been lost from the RAM.

Good question. I'm not 100% sure, but at that point I'd still expect
Self-Test to conclude with a displayed error (such as Calibration
RAM error, or RAM error, or ROM error).

So I'm still wondering what/why the CPU (U501) seems caught in an endless
RESET loop?

Does the instrument seem to respond to any front panel keys at all?

Just as a "sanity" check, it might be worthwhile to make sure *all* front
panel keys are free (and that none of them are stuck).

Sorry to hear none of the "easy" things were the cause so far.

--Greg

[Bob Smither]

Post by gbusg

Post by Bob Smither
Reset button? Don't see that.

The Reset function can be invoked by hitting "blue" (keyshift) key +
SGL/TRIG (TEST/RESET). (This might be only labeled "TEST" in blue on some
versions.)

Oops! Found it. Unfortunately activating it makes no difference.

Post by gbusg

Post by Bob Smither
I did this, but no change. I wonder if the boot process is assuming
something that has been lost from the RAM.

Good question. I'm not 100% sure, but at that point I'd still expect
Self-Test to conclude with a displayed error (such as Calibration
RAM error, or RAM error, or ROM error).
So I'm still wondering what/why the CPU (U501) seems caught in an endless
RESET loop?
Does the instrument seem to respond to any front panel keys at all?

Not at all - either plain key press or in combination with the blue key.

Post by gbusg
Just as a "sanity" check, it might be worthwhile to make sure *all* front
panel keys are free (and that none of them are stuck).

No difference in the endless cycle with any key press.

Post by gbusg
Sorry to hear none of the "easy" things were the cause so far.

Me too!

Many thanks for the good suggestions. I'm going to continue to poke
around in the digital section and see if I can find a bad part.

Best regards,
--
Bob Smither smither at c-c-i.com
=======================================================================
In all criminal prosecutions, the accused shall enjoy the right to a
speedy and public trial, by an impartial jury of the State and district
wherein the crime shall have been committed; which district shall have
been previously ascertained by law, and to be informed of the nature and
cause of the accusation; to be confronted with the witnesses against him;
to have compulsory process for obtaining witnesses in his favor, and to
have the assistance of counsel for his defence.
-- Sixth amendment to the Constitution of the united States
=======================================================================
Circuit Concepts, Inc. 281-331-2744
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smither.vcf
Type: text/x-vcard
Size: 140 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110828/5c8b39bd/attachment.vcf>

[Roy Phillips]

Bob
Is it possible that this has been left in the "calibrate" mode ? I seem
to remember that there is a DIL switch at the rear (number 8), for this
purpose. This is of course an instrument that is equipped with HP-IL, which
makes it a little less attractive, but otherwise a very well made DVM. Good
luck.
Roy


--------------------------------------------------
From: "Bob Smither" <smither at c-c-i.com>
Sent: Sunday, August 28, 2011 6:08 PM
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Subject: Re: [volt-nuts] HP3468A

Post by Bob Smither

Post by gbusg
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.

Done. All the supply rails look good.

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

The unit does not have that option.

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

I did this, but no change. I wonder if the boot process is assuming
something that has been lost from the RAM.

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

Reset button? Don't see that.

Post by gbusg
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).

Agreed.

Post by gbusg
Let us know how you come-out on it.

Will do.
Thanks for the feedback!
--
Bob Smither, PhD Circuit Concepts, Inc.
=========================================================================
Blessed is he who expects no gratitude, for he shall not be disappointed.
-- W. C. Bennett
=========================================================================
Smither at C-C-I.Com http://www.C-C-I.Com 281-331-2744(office) -4616(fax)
_______________________________________________
volt-nuts mailing list -- volt-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[Bob Smither]

Post by Roy Phillips
Bob
Is it possible that this has been left in the "calibrate" mode ? I
seem to remember that there is a DIL switch at the rear (number 8), for
this purpose. This is of course an instrument that is equipped with
HP-IL, which makes it a little less attractive, but otherwise a very
well made DVM. Good luck.

Thanks for the tip. I have tried both positions of the calibrate enable
switch - unfortunately no change :-(.
--
==========================================================================
Bob Smither Office: [phone] Fax: [phone] Bob at Smither.net
http://www.tx.lp.org LPT WebMaintainer
==========================================================================
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smither.vcf
Type: text/x-vcard
Size: 140 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110829/59efbf80/attachment.vcf>

[Bob Smither]

gbusg wrote:

<snip>

Post by gbusg
Let us know how you come-out on it.

Well, I may have found something. Signature analysis points to a
defective control ROM, U502. Markings indicate this is a Mostek
MK36752P. HP part number is 1818-1753. The pin out looks like that of
a Motorola MCM68764 UV erasable PROM, which I can get on EBay.

So, here is a real long shot - any chance someone the volt-nuts list
would have a listing of the contents of this PROM or know where to find it?

(I will be asking the
hp_agilent_equipment at yahoogroups.com Yahoo group as well.)

Thanks!
--
Bob Smither, PhD Circuit Concepts, Inc.
=========================================================================
13th Amendment to the Constitution of the united States:

"Neither slavery nor involuntary servitude, except as a punishment for
crime whereof the party shall have been duly convicted, shall exist
within the United States, or any place subject to their jurisdiction.

Section 2.a of Proposed House Resolution 163, 108th Congress:

"It is the obligation of every citizen of the United States, and every
other person residing in the United States, who is between the ages of
18 and 26 to perform a period of national service ..."
=========================================================================
Smither at C-C-I.Com http://www.C-C-I.Com 281-331-2744(office) -4616(fax)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smither.vcf
Type: text/x-vcard
Size: 140 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110829/3ad5fa84/attachment.vcf>

[Artekmedia]

Earlier posters suggestions to replace the RAM battery and to check the
power supplies for proper voltage and ripple is ALWAYS the 1st place to
start with this old gear (even if it is working!)

There is a group on yahoo dedicated to fixing and maintaining older HP gear

hp_agilent_equipment at yahoogroups.com

Lots of retired HP engineers quite possibly the guys who designed the
3486A even hang out there

Dave
NR1DX

Post by Bob Smither
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,
_______________________________________________
volt-nuts mailing list -- volt-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[Bob Smither]

Post by Artekmedia
Earlier posters suggestions to replace the RAM battery and to check the
power supplies for proper voltage and ripple is ALWAYS the 1st place to
start with this old gear (even if it is working!)
There is a group on yahoo dedicated to fixing and maintaining older HP gear
hp_agilent_equipment at yahoogroups.com

Thanks! I will check out the group.
--
=======================================================================
Bob Smither, Ph.D. Bob at Smither.net

I have a Dream:
First, Ron Paul becomes the Republican nominee.
Second, Dr. Paul becomes President Paul.
Third, our country becomes America again.
=======================================================================
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smither.vcf
Type: text/x-vcard
Size: 140 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110828/86e0ba0f/attachment.vcf>