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Rick,
Be prepared to pay big $$$ unless you happen to luck out and find a bargin.
Even a non-working 3458A goes for over $1000.
This instrument is rarely found in a non-working condition.
The general failure after 20 years is the CAL RAM battery running out of juice.
Good luck.
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Out of curiosity quick scan on ebay:
1 pc NOT working HP 3458A Multi-meter "For parts or not working"
Already at $2.132, 12 minutes to close.
Not related in any way to the auction.
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I agree with that. A few years ago 3458As with issue would go for $1500, I even saw some under a thousand.
Lately they are all over $2000, for example the unit mentioned on ebay in this thread, went for?$2,222.22.
It was an older unit, but did have option 002 (and 001).
The problem with trying to get a dead but complete unit is that a dead unit draws a lot of attention.
P/S issues are usually the easiest to diagnose and fix (IMHO), so I think those units draw attention from people hoping for an easy score.
--Victor
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My reaction when I read the subject title was, "Yeah, you and a few hundred others."
The recent introduction of the RoHS "black" edition indicates that Keysight isn't planning to replace the design. Old designs which are still in production hold their value well. The 34401A continued in production for an unusually long time because it was stipulated in so many test equipment lists in service manuals.
I picked up a couple of 34401As via ebay for ~$250 each. One was wonky. The cause was solder flux from an old repair. I cleaned it with isopropyl and it is the best of the pair. That's about 25% of the cost of the new equivalent. There are several on ebay now which will sell in the $200-300 price range. The same valuation puts an easily repairable 3458A at $2350. And an incomplete unit whether missing or unrepairable board at ~$1000-1500 as a parts mule. Provided it's not a set of known bad boards.
A working 3458A is worth $3000-5000. With RoHS compliant models available, there should be a drop in price on older units. But not likely to be huge.
Volt nutting has become rather fashionable.
Have Fun!
Reg
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Hello,
you also need to keep one more thing in mind which is bad for these seeking a cheap 3458A.
If you take a completely beat up one, and a decent lawyer, Keysight will - AFAIK - repair it for a reasonable set fee. This essentialy gives a new multimeter and puts a very high minimal bound on sales prices. If I would find a 3458A in the bin tomorrow and it was shot up with a Gepard rifle and was urinated on by both fox and female, as long as I can find all the parts, I would try to get Yaniv to force KS to honor its repair policy and flog the result on ebay.
Something I have had a lot of fun with is SolarTron. But I am not a big voltnut, my 7061 recently failed and I dont miss it so my wife balks heavily at the cal and repair cost.
Tam
With best regards
Tam HANNA
Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at
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On 2019. 12. 17. 18:47, Reginald Beardsley via Groups.Io wrote: My reaction when I read the subject title was, "Yeah, you and a few hundred others."
The recent introduction of the RoHS "black" edition indicates that Keysight isn't planning to replace the design. Old designs which are still in production hold their value well. The 34401A continued in production for an unusually long time because it was stipulated in so many test equipment lists in service manuals.
I picked up a couple of 34401As via ebay for ~$250 each. One was wonky. The cause was solder flux from an old repair. I cleaned it with isopropyl and it is the best of the pair. That's about 25% of the cost of the new equivalent. There are several on ebay now which will sell in the $200-300 price range. The same valuation puts an easily repairable 3458A at $2350. And an incomplete unit whether missing or unrepairable board at ~$1000-1500 as a parts mule. Provided it's not a set of known bad boards.
A working 3458A is worth $3000-5000. With RoHS compliant models available, there should be a drop in price on older units. But not likely to be huge.
Volt nutting has become rather fashionable.
Have Fun!
Reg
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For most people a HP3457A will be quite adequate if not quite as high of resolution. And much cheaper! But what bean counter struck off the display backlight?
Kjo
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I¡¯ve read that in some metrics, an HP3456A is slightly superior to the 3457A in practice, even if the 3457A might be a little nicer on paper. This isn¡¯t limited to the much improved LED display; the 3456A is slightly more stable than the 3457A if I recall correctly.
Unfortunately, the 3456A can¡¯t be digitally calibrated; you still need to adjust potentiometers.
With regards to the bean counter, he/she is probably the same one that struck the backlight off of my 3468A, in addition to a few other details that are inferior to my one digit less precise 3466A, like AC RMS accuracy and battery life. Sincerely, Dennis Chertkovsky
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On Dec 18, 2019, at 9:32 AM, Kevin Oconnor < kjo@...> wrote: For most people a HP3457A will be quite adequate if not quite as high of resolution. And much cheaper! But what bean counter struck off the display backlight?
Kjo
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Dennis,
At the time the 3468A was being developed, the LCD technology at Hp was in codevelopment with cooperation between the Loveland Instrument group and the Corvalis Calculator group.? There were no backlit LCDs at the time to be designed into the instrument.? This was a new technology.? We actually started with the LCD display from the 41C calculator in the engineering prototypes of the 3468A until the larger LDC eventually used in the 3468/78/57/88 was developed and prepared for manufacturing.? The 3468/78 and the LCDs were in development from 1978 -1981.? The project "KEY" for the 3468A was the first electronic calibration DMM for Hp.? ?The project began and started to ramp up after July 1978 and I joined as chief analog designer (5) for the front end signal conditioning in October 1978.? By February 1979 we had our full design team in place:
(1)? Project manager
(2)? Firmware/digital?
(3)? A/D and digital interface?
(4)? Hybrid switches and? DC? front end and attenuator
(5)? Ohms / AC / DC interface / Motherboard PCB and Input hybrid layout with fineline resistor networks
(6)? Power supply / battery backup / LCD? display
(7)? Mechanical and industrial design
Most of us were new engineers fresh out of university except for 3 members of the team (1),(2),(7)
The mission was to design a 5-1/2 digit DMM with full electronic CAL using less than 100 parts and for a parts cost of $100 or less.? We got close to the goal but had to increase the parts count because to meet safety requirements and that required for the necessary protection circuits for ESD and potential customer abuse.? That took more parts than first anticipated.
George Hnatiuk? ? Dec 19, 2019
Have a happy holiday
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George,
Thank you for the very interesting and insightful answer. I feel very honored to have an analog designer of my most prized multimeter directly respond to me.
I do have a couple questions about the 3468A if I may.
First, what aspect did you find most challenging to design and implement?
Second, if the budgetary requirements were lifted, what would you have done differently?
Third, if you had access to modern analog components (except for mixed signal parts like ADCs/DACs), what would you change?
Fourth, why did future models, like the 3478A, drop the battery power?
Finally, when open circuit in VDC mode on the 0.3V and 3V ranges, why does the voltage drift up and not down? I know 10^10 ohm input impedance makes open circuit drift inevitable, but it¡¯s interesting that it always drifts up on my meter. I am still impressed that a 5.5 digit battery powered reasonably portable meter exists at all. To my knowledge, no more precise portable DMM has been sold since (save for maybe one 6.5 digit Metrahit model, but its long term specs are about on par with the 3468A). I love being able to move it (and the 3466A) around my cluttered bench without having to worry about power cords and being able to charge them indefinitely when not using them. Again, thank you for all of the insight! Sincerely, Dennis Chertkovsky
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On Dec 19, 2019, at 8:06 PM, " ghnatiuk@..." < ghnatiuk@...> wrote: Dennis,
At the time the 3468A was being developed, the LCD technology at Hp was in codevelopment with cooperation between the Loveland Instrument group and the Corvalis Calculator group.? There were no backlit LCDs at the time to be designed into the instrument.? This was a new technology.? We actually started with the LCD display from the 41C calculator in the engineering prototypes of the 3468A until the larger LDC eventually used in the 3468/78/57/88 was developed and prepared for manufacturing.? The 3468/78 and the LCDs were in development from 1978 -1981.? The project "KEY" for the 3468A was the first electronic calibration DMM for Hp.? ?The project began and started to ramp up after July 1978 and I joined as chief analog designer (5) for the front end signal conditioning in October 1978.? By February 1979 we had our full design team in place:
(1)? Project manager
(2)? Firmware/digital?
(3)? A/D and digital interface?
(4)? Hybrid switches and? DC? front end and attenuator
(5)? Ohms / AC / DC interface / Motherboard PCB and Input hybrid layout with fineline resistor networks
(6)? Power supply / battery backup / LCD? display
(7)? Mechanical and industrial design
Most of us were new engineers fresh out of university except for 3 members of the team (1),(2),(7)
The mission was to design a 5-1/2 digit DMM with full electronic CAL using less than 100 parts and for a parts cost of $100 or less.? We got close to the goal but had to increase the parts count because to meet safety requirements and that required for the necessary protection circuits for ESD and potential customer abuse.? That took more parts than first anticipated.
George Hnatiuk? ? Dec 19, 2019
Have a happy holiday
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Dennis,
The most challenging aspect of the analog design for me was the overvoltage and? ESD protection of the Ohms converter current source using a minimum of CHEAP off-the-shelf parts.? I spent many months on this design which I will go through in detail in my DMM video tutorial.? ?Some of the design is quite clever in my opinion - (could it be anything else - LOL)
With no cost constraints and modern components, I would have chosen much better op-amps, voltage reference, and ohm reference resistor.? ?I think you are asking how one might soup up the 3468A.? This can be done and I will address this in my video series.? There are certain errors that are introduced by the input bias currents and offset voltages of the op-amps used in the Ohms and? DC circuits.? By proper analysis of the circuits, the important parameters can be identified to tell one how to select a given op-amp for the function desired to minimize drift over time and temperature.? You can only carry this so far of course because the input hybrid will eventually become the limiting factor.? ?Now of course if you wanted to get crazy about this, you could render the drift of the fineline resistors in the input hybrid U102 as a moot point by surrounding it in a temperature controlled environment but that is getting foolish since the A/D tops out at 300,000 counts.
The single most important imporvements that could be made is using a 40K? Vishay S102 series resistor for the Ohms reference and an LTZ1000 for the DC reference.
The design philosophy for the 3478A was different than the 3468A.? The 3468A was intented to be used as a portable bench instrument that could be taken out in the field with an Hp41C calculator for data acquition.? The 3478A was intended to be used as a system meter hence the HP-IB interface.? Plus as a system meter there needs to be an in-guard and out-guard to isolate the analog and digital sections when used as a system meter in a rack of other instruments.? This greatly stepped up the power requirements which made the battery backup option a non-starter.? Besides that, the 78 was NEVER intended to have battery power.? It was from the start conceived to be a rack instrument.
To further differentiate and justify the price difference between the 68 and 78,? marketing insisted (I objected and was over ruled) that the 78 have one more lower range on DC and Ohms.? You will notice that the 78 has a 30mV and 30 ohm range that the 68 does not.? ?All the circuitry and hooks are in the 3468A to have those functions but the firmware will not turn them on.??
Unfortunately,? I have no way to give you to access those ranges on the 3468A.? That would require a firmware change and these is no spare memory in the Intel 8048 and external chips to hold the required code.? If there was space, we would have put some "back door" way of doing it for testing etc. but we could not.? You could "cheat" the instrument into providing those ranges but that would require external jumpers between Input hybrid pins and would require you to be inside the instrument to manually move the jumpers around.? Besides the display would not position the decimal point in the correct place if you did that so other than to play and have fun, it has no practical use.
On the lower DCV ranges, the input impedance is typically around 10^12 ohms or more.? There is always stray capacitance in parallel with that so as charge bleeds into the input and charges the stray capacitance, the instrument measures the voltage on the capacitance and that is the drift you see.? ?The leakage currents that charge these strays are from the? POSITIVE sources of voltage which are more dominant around the front end of the instrument.? You are more likely to find drift upward due to positive leakage currents rather than negative leakages.? ?
Remember? ? ? Q =? C V? ? ?so? ? ? ? ? ??i? =? dQ/dt? =? C? dVdt
? ? ? ? ?hence,? voltage drift:? ? ? ? dV/dt = i / C
If leakage current is? ?i = 1pA? and? C = 10 pF? ?then the drift is? ? dV/dt? =? ?1pA/10pF? =? 0.1v / second
Thanks for the kind words.? It is hard for me to believe that I was in HP Labs 41 years ago designing the 3468A.? In many ways it seems like yesterday.? ?I have vivid and fond memories of those days and the people I worked with.? The KEY project was a new approach taken by Hp to the design and manufacture,? Our team worked closely with all the support groups from the IC, PCB, marketing, industrial design, machine shop departments and the production floor.? ?I made many good friends from all the various departments.? This was not a case where the engineers in the lab were isolated and thru specs over the fence to the support groups and waited from them to return a proto back to us.? ?I and the other engineers had our own work benches and we each built and tested our own designs and interfaced our modules into a central prototype we kept in our area.? We had no "offices" with doors.? Our desks and work benches were all together where we could see and talk to each other without getting up.? Of course that lead to a lot of pranks for stress releif and camaraderie.? ? A close working relationship with the support groups helped the success of the project.? For example,? the PC shop worked closely with us in developing an new coating process for the motherboard PCB to eliminate teflon standoffs (many in the 3455A and 3456A) to insure high impedance at critical nodes with feed-thru components.? This was a big breakthrough that helped keep manufacturing costs low.? Had that aspect of the PCB manufacture not been successful, meeting the design goals would have failed.? ?There were many new innovations that required various departments to pull off successfully and not just from us design team engineers.
Hope that helps you with your questions.
George Hnatuik, PE
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The most challenging aspect of the analog design for me was the overvoltage and? ESD protection of the Ohms converter current source using a minimum of CHEAP off-the-shelf parts.? I spent many months on this design which I will go through in detail in my DMM video tutorial.? ?Some of the design is quite clever in my opinion - (could it be anything else - LOL)
I remember admiring the Ohms current source protection in the 34401A, looks like it derives directly from the 3468A design.
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Siggi,
You are correct.? The Ohms current source and protection that I developed has never been improved upon.? It has been incorporated in every instrument since the 3468A/78A.? ?It is robust, simple with low parts count and very close to an ideal current source as you may ever find.? The dymanic Norton/Thevenin output impedance is greater than 10^15 ohms and can be made even larger with appropriate choice of Op-Amp that bootstraps the output FET and a few other component changes.? Such an output impedance cannot be maintained when integrated into an instrument.? The equivalent output impedance is degraded by moving the current from the ohms converter thru relays and the input terminals of the instrument not to mention all the nodes that touch the PCB that add unintended parasitic shunt impedances.
Thank you all for getting me to think about these issues again.? This has inspired me to make a huge effort to finish my design tutorial so others can leverage off the years of blood, sweat, and tears I "suffered" to get to where I am today in designing instrument analog front ends.
Wish you all a productive new year in 2020
George Hnatiuk. PE
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A parts unit just sold for $3250! The serial number is old, 9918. (Item #402001351594)
One plus is that the error flag is not on, but that can be cleared and have it look like it has no errors.
Victor
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George,
Thank you again for your detailed answers.
On the subject of a voltage reference upgrade, I do have a couple new LM399s laying around that could potentially be a drop-in vref replacement, I¡¯m sure I could find adequate voltage rails inside the 3468A for the heater, and the battery life wouldn¡¯t be too much reduced, but I don¡¯t have the time to properly age a voltage reference nor the equipment to properly recalibrate the meter after (my university research is in SMPS design; not exactly the most demanding of single digit ppm accuracy). This will be a nice project for when I have time to do it, as it should in theory give it most of the stability of a 6.5 digit DMM. I just hope the thermal gradients from the heat given off by the LM399 won¡¯t cause thermocouple effects within the meter that can¡¯t be nulled out.
The 40 k Vishay resistor seems mighty expensive, but I understand precision isn¡¯t cheap. Definitely a worthwhile upgrade once I find a way to properly calibrate the resistance ranges.
You¡¯ve got me curious; how exactly would I ¡°cheat¡± the meter into the locked out ranges? I¡¯m okay with installing switches or signal relays to add these functions to my meter, and I can just move the decimal point in my head. I currently am playing with various homemade thermocouples, so a 30 mV range would definitely help better measure them. In addition, a 30 ohm range would make roughly characterizing super low Ron power transistors less cumbersome.
Thank you for your explanation of the 0.3 and 3 V range high Z upward drift. I¡¯ll try measuring it with an LCR meter and a stopwatch.
Sincerely,
Dennis Chertkovsky
dchertkovsky@...
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Dennis, I missed this question of yours in "cheating" the instrument.? I will get back to you on that. Also, to all the fine people out there that have patiently waited for me to get my act together, the time has arrived and I will now be able to help you with any parts requests and information regarding the HP 34XX series of instruments that I helped design and develop.? I also have much knowledge and parts for some 33XX sources and? 35XX series of network and spectrum analyzers,? HP 41C and? HP85? series controllers and interfaces and series 300 workstations running HP? Rocky Mountain Basic, Pascal and HP-UX.? ? Back in the day, I built an HP3585A spectrum analyzer from scratch -- loaded all 52+ PCBs, put every screw in and aligned the IFs and tuned all the tweeks to get the instrument to within spec and better. If any of you still have needs,? please post them to this thread or EMAIL them to me at ? ? ? ? ? ? ? ?? ghnatiuk@...or go to my company web site to get contact information:? ?? I am not quite ready yet to offer the Red Devil precision resistors but getting close -- a few more weeks for that one. Thanks George Hnatiuk
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Dennis,
To you and everyone out there that need parts for the 34XX series of products, now is the time to renew your requests.? I should have the list of Red Devil resistors in a spread sheet sometime this weekend.? ?I uploaded a video showing my business move into a new location:
Parts requests can also be made in the comment section of that video.? Each person that needs parts could start his/her own thread in the comments.? That would help me keep everything straight with one location to go to rather than trying to refer to emails and these groups.
Thanks,
George Hnatiuk
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