Early 3458A A9 ref, T106382=LTZ1000A ? - Page 1
Forum section: electronics / general

author: TheSteve
author_rank: Unknown
timestamp: December 23, 2017, 10:58:19 pm
content: I just had a look at the A9 board on my reasonably early 3458A. Instead of being marked LTZ1000A the ref is marked LT T106382 date code 8809.Has anyone seen this before?Perhaps the same thing with a part # from before they decided on "LTZ1000"?

author: TiN
author_rank: Super Contributor
timestamp: December 23, 2017, 11:41:04 pm
content: I'm 99.9% sure it's same old LTZ1000AIf you want to know for sure, you'd need to drill the head off..

author: Macbeth
author_rank: Super Contributor
timestamp: December 23, 2017, 11:54:30 pm
content: That means there is a 0.1% chance it is an LTZ1000CH (non A), the resistors should reveal the truth...

author: chuckb
author_rank: Frequent Contributor
timestamp: December 24, 2017, 01:07:33 am
content: That's a neat find!The LTZ1000 was available a few years before 1988 so they had that base part number already. According to Pickering, then other people made suggestions for improvements and that was the LTZ1000A.Quote from: Flinstone on October 25, 2017, 05:40:33 pmIf the heater resistors are set up for 95 deg C (15k/1k?) you could measure the heater voltage (really Q401 Base voltage) on pin 1 of the J401 connector to determine if the chip is a LTZ1000 or a LTZ1000A.

author: manganin
author_rank: Regular Contributor
timestamp: December 24, 2017, 10:27:14 am
content: Quote from: Flinstone on December 24, 2017, 07:31:27 amThe HP part numbers were different, for example see the op-amp in the photo.The T-number usually means a pre production test sample. My guess would be the -A version based on the date code.

author: Pipelie
author_rank: Regular Contributor
timestamp: December 24, 2017, 10:56:37 am
content: Quote from: Flinstone on December 24, 2017, 07:31:27 amWhat about mine? I thought it is LTZ1000ACH, NOT check it yet.

author: Andreas
author_rank: Super Contributor
timestamp: December 24, 2017, 11:59:36 am
content: Quote from: TheSteve on December 23, 2017, 10:58:19 pmHello,strange. The LT1013 is blacktopped.Was that a usual thing of LT at that time?Blacktopping is something that I only know from counterfeit parts.with best regardsAndreas

author: quarks
author_rank: Frequent Contributor
timestamp: December 24, 2017, 01:08:22 pm
content: afaik all early HP 3458A hadthis1826-1860 HP part number for LTZ1000 and later switched to original LT part numberhttps://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg440601/#msg440601edit/correction: in a conversation with Flinstone I realized I mixed up numbers, my reply only refers to 1826-1860, therefore I corrected my reply.

author: TiN
author_rank: Super Contributor
timestamp: December 24, 2017, 03:56:29 pm
content: Indeed time to stable level is very different between chip versions. My A9 with CH chip takes about 5 minutes to settle at it's level (including lower temperature setpoint, 15K+100K), while standard ACH'es are seconds from cold state, due to 4 times better thermal insulation from the package.

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 24, 2017, 05:08:54 pm
content: All of my 5 LTZ1000 stabilize their oven temperature of 50°C within 15..30sec, in accordance with the datasheet value. See table inside my presentation of these 5 new kids on the block.The reference voltage takes longer, about 30min to <1ppm ..about 2h for full stability of <0.05ppm.Therefore, all of you should explain / define, to which criterion you're relating to.Frank

author: TiN
author_rank: Super Contributor
timestamp: December 24, 2017, 05:12:56 pm
content: My numbers were to 1ppm DCV readout match.E.g. 3458A (cold) connected to known LTZ ref output. Power on, start timer countdown till DCV readout reaches better than 1ppm tol from previous recorded value (measured by same unit, once it was hot for days).Heck, my CH-A9 3458 will even fail self-test if you run it one minute after the power on.

author: VintageNut
author_rank: Frequent Contributor
timestamp: December 25, 2017, 06:57:32 am
content: Week 14 of 19911826-1860 9114

author: TheSteve
author_rank: Unknown
timestamp: December 26, 2017, 04:27:15 am
content: Did some testing today, from cold to within 1 PPM of nominal value was 6 minutes. So most likely not an "A" version based on TiN's data.Quote from: Flinstone on December 24, 2017, 07:31:27 amNo coating on the board, but the LT1013 is coated on top. No rework ever done to the board, it is all original.

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 26, 2017, 10:54:05 am
content: Quote from: TheSteve on December 26, 2017, 04:27:15 amNope, These 5 min are related to the stabilization of the complete circuit, and this ispractically independent from A or non-A version.You need to monitor the Ube of the reference element, like I did, and there's the difference.Non-A takes 10...30sec, A version a few seconds only.Definitely search for my contribution and study the graphsFrank

author: Pipelie
author_rank: Regular Contributor
timestamp: December 26, 2017, 04:44:00 pm
content: There is an simple way to test it is ACH or CH.For CH version, the resistor between PIN4 and the metal can is very low, hundreds to Thousands ohm,but for the ACH version , the resistor is really high, if you use fluke 187 to measure it ,you'll get "OL"grab your DMM and test it, prove me wrong ,if you can.

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 26, 2017, 06:39:28 pm
content: Quote from: Pipelie on December 26, 2017, 04:44:00 pmThat makes sense, as pin 4 is zener negative and also substrate.If all LTZ1000 (non-A) used an electrically conducting chip glue epoxy, then pin4 is coupled to the case by the substrate bulk, having some resistance.As the chip of the A version is thermally isolated, the chip glue epoxy is very probably an electrically non conductive material.I'll check that in running condition, by probing the potential of the case of my LTZ1000 reference versus pin4.Frank

author: TheSteve
author_rank: Unknown
timestamp: December 26, 2017, 07:58:05 pm
content: The resistance between pin 4 and the can is beyond what a 34461A can measure - so a LTZ1000A(or very similar) it is. Which also makes sense as the board has no additional resistor for tempco compensation.

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 26, 2017, 09:55:08 pm
content: Indeed, the case of one of my LTZ1000 sits stable at +488mV, and the 120Ohm resistor at +476mV, measured with a 10 MOhm voltmeter.Frank

author: razvan784
author_rank: Regular Contributor
timestamp: December 28, 2017, 08:06:30 pm
content: Quote from: Flinstone on December 24, 2017, 07:31:27 am22-17-2052and they mate with 22-10-2052 on A1.

author: Pipelie
author_rank: Regular Contributor
timestamp: December 29, 2017, 05:28:36 am
content: Quote from: razvan784 on December 28, 2017, 08:06:30 pmyou can find it on Mouser, and Mouser #: 538-22-17-2052I ordered 10 pieces from Mouser several mouths ago.

author: mimmus78
author_rank: Unknown
timestamp: January 30, 2018, 12:42:35 am
content: Quote from: TheSteve on December 23, 2017, 10:58:19 pmWell yes someone already have seen this before ...Inviato dal mio ONEPLUS A5010 utilizzando Tapatalk

author: TheSteve
author_rank: Unknown
timestamp: January 31, 2018, 09:04:01 pm
content: Sorry, still don't get your post. My LTZ1000 has an internal Linear part #, yours has an HP part number which is well known and documented.

author: mimmus78
author_rank: Unknown
timestamp: January 31, 2018, 09:05:44 pm
content: Quote from: TheSteve on January 31, 2018, 09:04:01 pmYes just noticed too ... I deleted useless post.Inviato dal mio ONEPLUS A5010 utilizzando Tapatalk

author: Cerebus
author_rank: Super Contributor
timestamp: February 01, 2018, 12:59:57 am
content: Quote from: Andreas on December 24, 2017, 11:59:36 amMy guess is that they relabelled, with HP part numbers, some standard production LT1013s that already had LT part numbers because, for whatever reason, they didn't have any unencapsulated dies around to fulfil an order from HP.

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: February 01, 2018, 01:35:16 am
content: It was/still is a very common practice for OEMs to have parts labeled with their in-house numbers even if they are off-the-shelf common parts, in some cases it was because of some kind of selection process. This practice became very annoying once the OEM stopped supporting the equipment, they often didn't bother to release an equivalent's list. In some cases I was told that some OEMs ended their runs, the specification sheets were destroyed and even the manufacturer of the parts had to destroy their copies as well so later down the line they couldn't answer any inquiries about the part even when they had made it. Sometimes they didn't even know they had made the part in the first place, all the paperwork was gone.Great practice isn't it?

author: Cerebus
author_rank: Super Contributor
timestamp: February 01, 2018, 02:44:39 am
content: The thing I find really annoying is that, although all the components HP used got HP proprietary part numbers, most standard parts also had their standard part numbers called out in the service manuals (for a certain era of manuals) - except for the ones that didn't. So you've got a good chance of repairing old HP kit, unless the particular part that failed is one of the few thatonlyhad a proprietary part number, then you're left guessing or trying to characterise the failed part from a working part and then scouring datasheets for a part that matches. Grrrr...