Pearls of the Past (Only for the Voltaically Inclined) - Page 1
Forum section: electronics / projects

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 07, 2013, 04:02:14 am
content: I guess my real entry into obsession (I will never be really hooked) starts here:I found 2 pcs. on fleabayWhat it is?If you don't already know, you probably don't care.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 07, 2013, 04:25:52 am
content: Well - I find little or no info about it, and it doesn't look exactly as I would have thought. But it is supposed to be an original HP part:1820-0001 AMP, REFERENCE(I believe it - but I am willing to be wrong just for the fun of waiting for these two sexy toys to arrive from America).If it was just another regulator it should not be stamped C&A ... Here is my guess (I like the drawing, so I borrow it from Russia):

author: fmaimon
author_rank: Unknown
timestamp: November 07, 2013, 04:35:22 am
content: Probably a Fluke part. Used on their DC standards, like the 731A, 731B, etc. While it was made by Motorola, it was called SZA263, now it is called LTFLU-1, as it is made by Linear Technology for Fluke.http://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http%3A%2F%2Fwww.eefocus.com%2Flymexbg2vo%2Fblog%2F10-01%2F183124_69352.html

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 07, 2013, 04:37:40 am
content: And if I am right, I can build me a DIYhttp://www.ko4bb.com/Manuals/Fluke/Misc/732A_Users_Manual.pdf- see Fig. 8-5a, Sheet 2 of 3.And if I am wrong, never mind. Well worth the gamble ...

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 07, 2013, 04:39:30 am
content: Quote from: fmaimon on November 07, 2013, 04:35:22 amHah - you beat me by seconds, and destroyed my dramatic openingI hope we are right. Thanks for supporting my game ...

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 07, 2013, 11:12:38 am
content: Ramp Reference QCR1 1820-0001 transistor&diode Mot ---Designed of the HP 3440A started about 1961 and HP sold ituntil about 197?.HP will build and ship more than 10,000 HP 3440A digitalvoltmeters in only five years.The electronics of the 3440A are designed by Chuck Near and DaveCochran. Chuck Near was fresh from MSU Engineering school whenhe worked on the 3440A design.The HP 3440A Digital Volt Meter has a full scale of 10,000counts with a 5% over-range. It has a digital output and adigital control input - neither are IEEE-488.The HP 3440A was HP's 2nd DVM. The first HP DVM was themodel 405 which was all tube.Source:http://www.pa.msu.edu/~edmunds/DVM_HP_3440a/dvm_notes.txt

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 07, 2013, 11:22:27 am
content: DESIGN APPROACHThe Model 3440A Digital Voltmeter uses a voltage-to-time-intervalconversion system as outlined inFig. 3. The time interval is evaluated by digital counter techniquesto obtain the digital display.The unknown voltage, appropriately attenuated, is applied to acomparator to which a linearly-decreasing ramp is also applied. Whenthe ramp voltage becomes equal tothe unknown voltage, a coincidencepulse is generated, as shown by thetiming diagram in Fig. 5. The rampvoltage is also applied to a zeroreference comparator which has signal ground for its other input.Again, when the ramp voltage becomes equal to signal ground, acoincidence pulse is generated bythis comparator. The time difference between these two pulses is adirect analog of the difference between the unknown signal voltageand signal ground.The time difference is convertedto digital form by the counting ofclock pulses. The first-occurringcomparator coincidence pulse opensa count gate, enabling the countersto operate, and the second pulsecloses the gate to terminate thecount. The first comparator pulsealso starts a Colpitts oscillatorwhich provides the clock pulses.By appropriate choice of rampslope (400 v/sec) and clock pulserepetition rate (400 kc) the totalcount displayed corresponds to input millivolts. Range switchingoperates an input attenuator andplaces the decimal point so that thedisplay reads directly in volts.Source:http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1963-11.pdfp.3

author: sync
author_rank: Frequent Contributor
timestamp: November 07, 2013, 02:13:06 pm
content: It's maybe used in the 3450A too. Unfortunately there is no part number in the service manual. To make it good it's temperature controlled by a petier element. A LM399 is probably better.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 07, 2013, 02:50:41 pm
content: Thank you very much for the beautiful nostalgic schematic."An LM399 is probably better"? Yes, sure.[Edit all]If I eat noodles for a month, I can buy a legion of LM399 today. The two devices I have found in the fleabay bush of Texas, USA are analog collectables. They are unnused original spare parts produced by Motorola and bought/packed by HP sometime in the 1960s/early70s. So we are talking about 40 years old RefAmps. In the mail list they are classified as 'unobtanium'.I really like the schematic. It is built like a classic power supply with constant current through the temp compensated ref diode and a precision diff amp for gain. Typical HP quality "engineer" design. Could you please give a link to the manual.---[Notes for my next search MHQ2221 MHQ2229 4JX19A519, 4JX19A555]

author: sync
author_rank: Frequent Contributor
timestamp: November 07, 2013, 04:36:43 pm
content: You can get the 3450B manual fromhttp://cp.literature.agilent.com/litweb/pdf/03450-90007.pdf. Regarding collectibles. I got the whole thing.

author: c4757p
author_rank: Super Contributor
timestamp: November 07, 2013, 04:45:12 pm
content: Ooh, wow, that is one good-looking multimeter.

author: calexanian
author_rank: Super Contributor
timestamp: November 07, 2013, 05:46:33 pm
content: How many of those did it take to get us to the moon?

author: SeanB
author_rank: Super Contributor
timestamp: November 07, 2013, 07:03:28 pm
content: 11..........

author: calexanian
author_rank: Super Contributor
timestamp: November 07, 2013, 11:47:25 pm
content: My guess is that they hand matched the transistor and the zener, soldered them together, and molded a case around them with those nifty looking gold plated pins sticking out. Hmmmmmm....... Oh yeah, we call that value added today! Thought that sounded familiar. Hand matched 2n5551 with a collector resistor and ratio metric bias set and emitter transistor. Overmold it in black plastic, and, Bingo! 150 volt amplifier module! Ready to be marked up %1000 and sold as a special selected front end amplifier for all your snooty needs! hahahahaha. It would be funny if it did not really happen!

author: mamalala
author_rank: Unknown
timestamp: November 08, 2013, 12:46:04 am
content: Quote from: calexanian on November 07, 2013, 11:47:25 pmYou do understand that this is not about simply sticking a bunch of parts in a 5$ multimeter an select them by what the display says, right? You do, i hope, at least have an idea that simply selecting a manufacturer and part, that shows the desired parameters over time, is a time consuming task? And that, after a small range of different parts is chosen, evaluating them further requires even more time and folks working on that? Not to mention the resources required to do aging tests. After all, you want to make sure that a part is within specs for, say, 10 years. Do you have any idea what is involved to check for that in just, say, one year?And finally, i hope that you are aware that precission instruments have rather low sales numbers, compared to the 5$ multimeter you probably would use to select parts? That means that all the time, money and resources spent on these things have to be paid by far, far fewer customers, compared to mass-market devices.Greetings,Chris

author: calexanian
author_rank: Super Contributor
timestamp: November 08, 2013, 02:56:30 am
content: My comments are in jest...... One of my jobs involves Mill-PERF testing and I have great sympathy for the engineers of that time period. This company also makes occasionally EA53 tubes. Look that one up and see what it was used for! If I ever have to get them qualified again to make that one I am gonna take out extra life insurance!

author: Six_Shooter
author_rank: Regular Contributor
timestamp: November 08, 2013, 04:38:14 am
content: Quote from: sync on November 07, 2013, 04:36:43 pmExcuse me while I change my pants...One day I will own some bench gear porn like this.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 10, 2013, 03:47:01 am
content: Yes - a fine instrument.Anyone has studied the temperature sensing and regulation of the Fluke 732A? There are several thermistors - batteries, oven, front panel (room temp?) - and one more (?) that I cannot find. The schematics are herehttp://www.ko4bb.com/Manuals/Fluke/Misc/732A_Users_Manual.pdfpp. 93-113.In this detail - why is base and emitter of Q5 shorted?

author: SeanB
author_rank: Super Contributor
timestamp: November 10, 2013, 09:21:52 am
content: Reverse bias protection for U2. Prevents reverse voltage on the BE junction from getting high enough to zener the junction, which will degrade it with time.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 10, 2013, 09:37:57 am
content: Quote from: SeanB on November 10, 2013, 09:21:52 amThanks. So if I understand - the normally reverse biased BC junction of Q5 will shunt the BE junction of U2 in case the latter becomes reverse biased. If so, it has nothing to do with temperature compensation?

author: SeanB
author_rank: Super Contributor
timestamp: November 10, 2013, 09:47:10 am
content: Just a very cheap and very low leakage diode. The reverse leakage is so small that it will have no affect on the reference bias up to temperatures where the solder on the devices melt. It protects the reference during power up and power down if the rails decay at different rates, or if a supply rail fails in operation.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 10, 2013, 10:21:06 am
content: Thanks. Anyone familiar with the rest of the large advanced analog ref schematic, and want to share their knowledge/skills in the form of pointing out what is absolutely necessary for a small DIY ref board with the transistor+diode part?

author: david77
author_rank: Frequent Contributor
timestamp: November 10, 2013, 10:28:53 am
content: Quote from: sync on November 07, 2013, 04:36:43 pmSorry for the OT:Is that the one that was on ebay.de a few weeks ago? I was very much tempted to get it myself, took a lot of self control.Could you let us have a sneaky peek inside, please?

author: sync
author_rank: Frequent Contributor
timestamp: November 10, 2013, 03:50:07 pm
content: Quote from: david77 on November 10, 2013, 10:28:53 amYes, it's the one from ebay.de. I only have a phone as camera. Taking acceptable pictures is a pain. Here is a teardown (not from me):http://www.josvandijken.nl/elektronica_Hewlett-Packard_3450A.php

author: mamalala
author_rank: Unknown
timestamp: November 10, 2013, 05:13:07 pm
content: Quote from: sync on November 10, 2013, 03:50:07 pmWhat a nice machine. I'm wondering if it was some kind of standard back then to build stuff in such a modular fashion? I have a Fluke 8502A, which is also full of plugin-modules for pretty much all of it's functions, and it dates to the 70's and 80's.Greetings,Chris

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 10, 2013, 05:43:10 pm
content: Quote from: mamalala on November 10, 2013, 05:13:07 pmIt was. This super size base board from a very expensive HP gadget vandalized in Israel cost me USD 12. If I live long enough it will be a Voltage Reference Nursery.

author: mamalala
author_rank: Unknown
timestamp: November 10, 2013, 05:56:58 pm
content: Quote from: quantumvolt on November 10, 2013, 05:43:10 pmI think i know which seller you got that from. Sells loads of stuff that looks like it has been pulled direcetly out of a war zone. After thesee things became the targets and have been hit, that is.Wondering what the reasons are that nowdays you rarely (if at all) get such a nice modular unit design, apart from some bean counters wanting to save some bucks for connectors. My HP 5345A counter is also nicely modularized. Should make pictures of the insides of these two units. Marvels of engineering.Greetings,Chris

author: sync
author_rank: Frequent Contributor
timestamp: November 10, 2013, 06:11:29 pm
content: I think the reason for the old stuff is simple. They need a lot of PCB area. One big PCB isn't enough. So using a back plane and lots of cards is a good solution and easy serviceable. Today all of this fits on a small PCB. No need for expensive connectors, more hand assembly and so on.btw: quantumvolt, did you see this?https://www.eevblog.com/forum/testgear/fluke-732b-dc-standard-teardown/. DIY one would be hard.

author: mamalala
author_rank: Unknown
timestamp: November 10, 2013, 06:27:20 pm
content: Quote from: sync on November 10, 2013, 06:11:29 pmFair enough. Not having seen much of the insides of modern high-spec equipment, i'm wondering if they go for (more or less) single board stuff there as well, since i can see certain benefits in a moduler design for such things. But then, maybe it's just me, simply liking such modular stuff.Greetings,Chris

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 10, 2013, 06:34:38 pm
content: Quote from: sync on November 10, 2013, 06:11:29 pmYes, I've seen it. I even posted a link to a schematic there.I have no aspirations at all of coming close to the real thing. But what I will make out of the two HP/Motorola diode+transistor devices will be comparable to the Krohn-Hite boxes based on 1N829 and a chopper amp. As I have the refs and a LTC2057 chopper amp, all I need to buy is 2 super stable resistors for a single 10 V output. The temp feedback circuitry for the last mV or so is tinkering and will be a project in itself.I like to make experimental setups. I never finish anything. And I am not interested in owning real old quality measurement equipment - only studying the schematics. I guess I am in this for learning.My 'scope' was a 10 dollar external USB sound card with level shifter and DC coupling. I almost fried my laptop with it. So for me the most important thing is to get a brand new hobby all round oscilloscope. Then I canmore than numbers.But I like to look at other peoples old gear...

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 13, 2013, 01:43:05 am
content: JFYI - I sent a polite email to Agilent asking if there were someone who had knowledge about these refs. It is now beyond any doubt that they are HP parts (not Fluke).http://www.pa.msu.edu/~edmunds/DVM_HP_3440a/hp_3440a_dvm_manual.pdfThey hardly answered any of my questions at all. Seemed totally uninterested (the author of the reply had been with HP/Agilent for 25 years and stated that it probably was a "heated reference" - WTF ... they didn't even check their archives? As is seen in my links here and in earlier posts it is open to anyone that searches for it that the part probably is a REFAMP diode+transistor from Mororola.So much for HP Memory ...http://www.hpmemory.org/timeline/dave_cochran/hpj_nov63.htm

author: sync
author_rank: Frequent Contributor
timestamp: November 13, 2013, 02:15:33 am
content: btw: In the 3440A manual the manufacture of QCR1 is General Electric and the GE part number is 4JX19A519. And look at this page:http://www.nsnlocator.com/nsndetail.cfm?NIIN=008522869&pn=1820-0001. There are alternative part numbers.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 13, 2013, 02:27:32 am
content: Yes. Probably depends on the year (1963 is - just to say it - 50 years ago). Of course I checked in the manual that I took the photo from and linked to over - and the part QCR1 is not even in the parts list of the very same manual that uses it in the schematic (?). That is - AFAI can see.But IMO that changes nothing. If you look at my first post here you will see a photo of the Motorola part. So that must have been used in a revision that I cannot find the manual for. That was one of the things I asked Agilent about.And it still isn't a LMx99 or a LTZ1000 or any "heated reference".EDIT: Where (in which manual- the one I link to?) do you find QCR1 in the parts list for the Ramp generator Assy? Please also give page. I can't find it.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 13, 2013, 03:52:58 am
content: Quote from: sync on November 13, 2013, 02:15:33 amI looked at your link once more - it says: 1820-0001, 1820-0006, 48A51151C01, 4JX19A519, 4JX19A555, SCA11, SZA11.The last one SZA11 is afaik a Motorola part. The Fluke REFAMP from Motorola is designated SZA263.

author: sync
author_rank: Frequent Contributor
timestamp: November 13, 2013, 02:10:10 pm
content: Yes, I also think that SZA11 is a Motorola part number. Maybe your 1820-0001 is a SZA11.Quote from: quantumvolt on November 13, 2013, 02:27:32 amIn your linked manual. On page 7-9.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 13, 2013, 02:57:46 pm
content: Thank you very much. I must be blind. And also dumb to doubt the old manual. One of my ideas is that an instrument is only as good as the quality of its manual, and the old HP manuals are really serious, almost scientific documentation.So I say "Sorry" to the authors of the manual for doubting their document

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: November 17, 2013, 11:47:35 pm
content: Quote from: quantumvolt on November 10, 2013, 10:21:06 amThis thread has been great fun for me, hehe. After reading the 732b teardown (which was wonderful), my next stop was the732b User's ManualThe "theory of operation" section was excellent. Have you read it yet? I think it answers your question.

author: echen1024
author_rank: Super Contributor
timestamp: November 18, 2013, 03:30:51 am
content: Quote from: quantumvolt on November 07, 2013, 02:50:41 pmI am in Houston, TX. If you need a freight forwarding type of thing, let me know...

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 18, 2013, 04:02:54 am
content: Nice somebody find fun here - I hope there will be more. This thread will renew the never lived life of the two 40+ yo refs. I look forward to getting them.Even if I paid more than USD30 in shipping and postage for an envelope ("International Letter"), the USPS is not much faster than China Post. At least not to Thailand, that is. But I can waitProduct & Tracking InformationPostal Product:Features:International LetterDate & TimeStatus of ItemLocationNovember 8, 2013 , 6:39 amProcessed through USPS Sort FacilityCHICAGO, IL 60666November 7, 2013Depart USPS Sort FacilityCOPPELL, TX 75099November 6, 2013 , 8:56 pmProcessed through USPS Sort FacilityCOPPELL, TX 75099November 6, 2013 , 4:00 pmAcceptanceGARLAND, TX 75042November 6, 2013Electronic Shipping Info Received

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: November 18, 2013, 04:38:46 pm
content: Have you got a rig to measure tempco vs current yet? That'll give you something to do while you wait

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 19, 2013, 11:28:21 am
content: Quote from: Galaxyrise on November 18, 2013, 04:38:46 pmNo, I haven't. And I won't make one. Preparation takes imo much of the fun out of it. I will clear the path as I walk it.My first rig will be a 7812 regulator, a metal film resistor + 100 ohm trim "current source", a 2 dollar fleabay digital thermometer and a Processing sketch that maps ppm-level (of course limited by my best measuring instrument Agilent 34401A which obviously is not good enough for this project). When I get to learn what I am up against, I will improve the setup step by step.As everyone knows - the only way to "make" a Fluke box is to buy one ...

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: November 19, 2013, 04:48:39 pm
content: You'll want some kind of "oven" too. I've got a cheapie thing I built which is just some incandescent night lights in an outlet box with a dimmer.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 21, 2013, 03:09:34 am
content: Well - they are here...

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 21, 2013, 03:19:25 am
content: It might take a week or two before they see any electronsI need advice on a test circuit. I don't mean "use precision resistors" and so on - I mean the schematic and values/critical components. Oven, thermistors and other fancy stuff will have to wait. First goal is a reasonable circuit with a working and stable feedback.My first attempt on making a simple oven-less hybrid from the two manuals:http://www.ko4bb.com/Manuals/Fluke/Misc/732A_Users_Manual.pdfpp. 111-14http://www.ko4bb.com/Manuals/Fluke/Misc/732B_734A_Users_Manual.pdfp. 60Knowledgeable comments would be highly appreciated.

author: Andreas
author_rank: Super Contributor
timestamp: November 21, 2013, 06:02:23 am
content: Mhm,is it really a genuine refamp? in a molded case and not hermetically metal can?the SZA263 was in a metal can.http://www.amplifier.cd/Test_Equipment/other/images/Fluke5442A_8_SZA263.jpgThe fluke handbook silk screen shows that the fluke refamp is smaller than a TO-99 case (probably TO-46)With best regardsAndreas

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 21, 2013, 06:26:36 am
content: Quote from: Andreas on November 21, 2013, 06:02:23 amI wrote in my 2nd post in this thread:"Well - I find little or no info about it, and it doesn't look exactly as I would have thought. But it is supposed to be an original HP part: 1820-0001 AMP, REFERENCE"So I have to leave your question as one of metaphysics and semantics. I do not have and have never seen a "genuine" REFAMP.I have never claimed it is a Fluke part (although another poster suggested it was so)- I have repeatedly said it is claimed to be a HP part made by Motorola. If it has a SZA-name it would probably be SZA11 (se earlier post). It is - however - a "hybrid" of a transistor and a Zener diode (as is SZA263 and LTFLU-1).You do not need a metal can or any special production technology parts for circuits that combine a transistor and a diode for making a net tempco close to zero. You can handpick discrete components and enclose them in thermally conductant chewing gum.These parts - unless they are "fakes" (me thinks not - they were bought from one of the biggest American ebay dealers in used instruments - selling everything from original spare resistors to spectrum analyzers priced at multi-thousand dollars - all with good ebay feedback) were used in HP3440 and maybe -3450 from 1963 (HP3440). Anyone who feel compelled to do so, please check their "history"...

author: quantumvolt
author_rank: Frequent Contributor
timestamp: November 21, 2013, 04:16:50 pm
content: Well - seek and you will find (at least if it is an HP instrument - the ultimate in documentation).The original "AMPREF" (since the HP use of the transistor-diode from Motorola as a temp-compensated reference amplifier "REFAMP" is documented already in 1963, I now assume that FLUKE copied the idea from HP). The big, black, molded case AMPREF is clearly visible behind the two trim pots (black and blue below the metal 'bridge' with the text '... instrument is on').The reference assembly board placement from the manual:The AMPREF (QCR1A&B) placement on the reference assembly board - and the two trim pots (R60 and R51):Source manualhttp://www.pa.msu.edu/~edmunds/DVM_HP_3440a/hp_3440a_dvm_manual.pdfSource picture (the whole instrument - top view)http://www.hpmemory.org/pict/timeline/dave_cochran/hp3440a_top_hr.jpg

author: Andreas
author_rank: Super Contributor
timestamp: November 21, 2013, 09:09:32 pm
content: Hello,fine. that convinces me.But since most semiconductors at that time were within hermetical (metal) packages, it explains that one could be easily in doubt.Fine instrument with all those metal can semiconductors.With best regardsAndreas