Author Topic: HP 973A & 974A Multimeter Service Manual anyone?  (Read 1197 times)

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Offline AMR Labs

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HP 973A & 974A Multimeter Service Manual anyone?
« on: December 30, 2018, 04:01:02 pm »
I recently acquired a HP973A DMM as an addition to my other three fully working HP974A's as in my opinion these are outstanding instruments, even though the "970" series (971A, 972A, 973A, and 974A) dates back to around 1994-2000 they will easily hold their own against any comparable Fluke, and remarkably only at a fraction of the cost. All of them except for one where basically still dead on calibrated after all these years. Built quality is excellent, both inside and outside, as with any HP product. Incidentally these where manufactured in Japan. Maybe by a major Japanese electronics company under contract for HP? Or under license?

So far I have tried to locate any web reference to a schematic or service manual for these DMM's without any luck. Same goes for the HP/Agilent website, and on the HP-IO group's messages. At this point I am not even sure there even where any service manuals that got released, as all hits always only seem to point to the user manual or brochures/spec sheets. The user manual (is more like a leaflet), in comparison to conventional HP manuals, is quite limited on technical and maintenance information, and contains no schematics or diagrams other than the location of the internal cal points and a calibration sequence.

Does anybody (that may have worked at HP, or otherwise) know if there where actually any service manuals for these DMMs that where made available? In my mind I would think there must be something out there as HP would most definitively have created some kind of detailed service literature, or at least a schematic for these DMMs, but maybe due to cost cutting measures the service information was excluded from the standard user manual. Then again these where manufactured in Japan, so maybe the company that made them under the HP brand actually never released any service literature in normal HP tradition.

Anyway, I would be very interested in anything technical related to the 973A/974A, other than the standard user manual or spec sheets. Or even to find out about the story of why this 970 series of DMMs where manufactured in Japan, which seems a bit odd for an HP product.

BTW the HP970A DMM is not really in any way similar to the rest of the 970 series I am interested in, but is more like a hand held probe style meter, for which there is some information available on the net.

Thanks for any leads.

EDIT: Added JPG image.
« Last Edit: December 30, 2018, 04:10:01 pm by AMR Labs »
 

Offline Tomorokoshi

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #1 on: December 31, 2018, 06:33:23 am »
Hewlett Packard was in a joint venture with Yokogawa Electric from 1963 to 1999:
https://en.wikipedia.org/wiki/Hewlett-Packard

Specialty meters and impedance analyzer equipment were some of the key products from there:
www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1966-09.pdf

It may help to look to see if there is an equivalent Yokogawa Electric product.
 
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Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #2 on: December 31, 2018, 12:08:17 pm »
Thank you very much for that info, very useful. A step closer to possibly finding what I am looking for.

Sounds possible that these 970 series multimeters might be an original product from the Yokogawa company that where relabeled as HP.
« Last Edit: December 31, 2018, 12:11:12 pm by AMR Labs »
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #3 on: December 31, 2018, 12:46:16 pm »
I did send an email inquiry about the service manual to Yokogawa, hope they will reply back.
 

Online Kosmic

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #4 on: September 15, 2019, 01:27:27 am »
Look like the HP 970 series is similar to the Yokogawa 7537 series

Yokogawa 7537:




http://almateks.com/doc/dmm-e-150.pdf

My HP 974a:

« Last Edit: September 15, 2019, 01:32:25 am by Kosmic »
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #5 on: September 15, 2019, 03:08:30 pm »
Interesting information, thank you for posting it here. So in the end the suspicion was confirmed that the HP97xA lineup was a rebranded Yokogawa product.

So it seems their model 7537 "4" 20KHz True-RMS and 0.1% accuracy specs are equivalent to the HP973A, one down from the HP974A 100KHz True-RMS & 0.05% accuracy top of the line model. And apparently there is no Yokogawa 7537 model that would have been equivalent to the 974A. The above internal view pictures are exactly the same as the HP version I have, so no doubts left regarding it being the same product. Rebranding not withstanding, they certainly perform very well and are fully up to par to carry the HP logo in terms of quality and long term reliability. None of the 4 HP974A's (5 by now - found another brand new one and still in the box so could not resist) I own is off by as much of a percentage fraction of the reading from either my HP3478A/3468A, even after all these years since they where last manufactured, and without having as so much to touch up on any calibration at all.

The only one from the batch I own that I actually needed to recalibrate was the 973A as it came with quite a bit of battery corrosion inside that had fortunately not spread beyond the battery holder but the acidic vapors had over time apparently deposited on some areas of the PCB causing lower resistance paths here and there not allowing the instrument to zero on some ranges etc. Spot cleaning with alcohol did not help. The solution was to wash the whole PC board with some dishwasher detergent and a soft tooth brush, then dry out with moderate heat. Then recalibrate according to the procedure in the owners manual. It has worked flawlessly ever since.

I wonder why there doesn't seem to be any 974A direct Yokogawa equivalent in their 7537 lineup. A model "5" would probably been the denomination given. Perhaps it would have competed against some other of their own top of the line model they already had on the market...

In any case still no luck finding a schematic for these, even at the Yokogawa website the search for the 7537 series raises no results. When I contacted Yokogawa some time ago to ask about the HP97x service manuals or anything they would have on that lineup, I finally got a reply from one of their Technical Support & Calibration Engineers in Europe (after about a month and 3 different messages sent to them) that they did not have any records left about the HP lineup or the Yokogawa equivalent models as they had been "long discontinued", and instead only sent me the copies of the HP owners manuals that are already circulating online. So what company (huge company) completely and absolutely disposes of records for their not so really that "very long ago" discontinued products, and bear in mind this was a product (at least the HP version) that was still widely available late 90s/early 2Ks. Oh well, guess Yokogawa did it, maybe did do not have the storage space, or they just plain don't feel like releasing their schematics or service info that is perhaps still lingering inside some boxes or file cabinets somewhere around the factory.

Thanks again for this lead, and I will post any updates if I am able to find any further information online.
 

Offline Tomorokoshi

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #6 on: September 15, 2019, 03:45:15 pm »
...

So what company (huge company) completely and absolutely disposes of records for their not so really that "very long ago" discontinued products, and bear in mind this was a product (at least the HP version) that was still widely available late 90s/early 2Ks. Oh well, guess Yokogawa did it, maybe did do not have the storage space, or they just plain don't feel like releasing their schematics or service info that is perhaps still lingering inside some boxes or file cabinets somewhere around the factory.

Thanks again for this lead, and I will post any updates if I am able to find any further information online.
I've seen this quite a bit, both generally and at companies I have worked at. The dynamics are typically something like:

1. Marketing specifies some market segment. Cursory research is done, and an engineering and manufacturing team is put together.
2. It gets designed and manufactured, sold for a while, then obsoleted.
3. After some time, perhaps 5 years after obsolescence, the remaining repair parts are disposed of.
4. Schematics and other drawings are not generally accessible by customer support. From their point of view, it's all gone even if copies may be somewhere, whether on computer or microfilm.
5. All the people involved with the project have long since moved on.
6. From a business case point of view, there is no ROI (Return On Investment) by maintaining access to "old, obsolete" data that long.
7. Managers tend to have very little passion for obsoleted products.

Classical Hewlett Packard equipment, where a fair percentage of documentation remains available, is an outlier compared to others.
 

Offline Kleinstein

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #7 on: September 15, 2019, 03:55:59 pm »
Yokogawa is now part of Keysight. There are other instruments made in Japan that are more or less identical under Yokogawa and HPAK name.

While a good quality DMM, 3.5 digit DMMs are usually not really serviced if there is something seriously wrong (e.g. more than fuse or battery contacts). So in this case no really important data missing.

In the process of going from paper base documentation to electronic form some documents may get lost. This also happened with early computer systems - so the docs may be still there on some 8 inch floppies or old MO drives or write only tape. The merger could also be a reason to get rid of old paperwork.
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #8 on: September 15, 2019, 05:42:22 pm »
To Tomorokoshi:

Following are my personal views and opinions, and I fully understand your points and don't wish to argue about them. Just wanted to air my "grievances" to the point and say my peace. I have been into electronics both professionally and as a hobby most of my life, and it has been a rare occasion (specially with the advent of the Internet) that one cannot find service information or even a simple schematic of any given electronic equipment in order to do my own repairs. Even sometimes finding something that is "similar" will do the trick and save the day. But in the case of these Yokogawa 7537 | HP97xA line of DMMs it is the first time in my life that it has been so far impossible to locate absolutely anything at all, other than the user manuals, and everything else seems to be shrouded in a veil of mystery. Maybe the service manual has written TOP SECRET across it? ;-)

How does it hurt the company ROI to just voluntarily release the service information to the public domain of a discontinued product, specially if the company does not want to do anything further with it. It might even possibly save them more than a few service calls! It is understandable that the company does not want or it even makes sense to any longer manufacture and keep stock of parts for older discontinued products beyond their "in-support" period. No spare parts available anymore? fine, let me deal with it and there will always be parts mules out there, or creativity, ingenuity and improvisation might take place as long as it is worth the effort. But why hoard, hide or conveniently "misplace" or even destroy any technical service information? Again: how disclosing this information at the appropriate time can hurt the company ROI? They will always count on their sales to corporate client purchases which have their own in-house obsolescence and replacement cycles in place, and that definitively will keep on buying from the same source no matter what,  as long as the deal numbers are right. I would think those sales are the ones that really matter the most to the ROI.

I don't think it would hurt the [real bottom line] sales figures that in general giving a limited percentage of here and there owners possibly the ability of fixing up their discontinued equipment. That instead of them running to the store to buy a newer model from the same brand, which I doubt happens consistently anyhow just because one cannot fix the current one anymore due to lack of information from the manufacturer. I would think that a good part of the long standing Bill & Dave's HP brand tradition success to this day and well beyond the HP era itself is because of easy access to service information even for older discontinued products and keeping them going while they are still getting the job done (talk about boosting YOUR own ROI). Plus just the fact that the service information for most existing HP models was released at some point to the general public (probably around the time when the first name change came into the picture) comes across as a good faith "nice guy" action that will not only bring more luster to the brand, but also more individual (non-corporate) customers would actually consider buying again from the same company. In any case I would think that the bulk of sales for a big company like Yokogawa does come from corporate purchases that don't give a fig about service information being available at the time or in the foreseeable future. So why hurt the individual user by not making this service information available.

To me in particular, and speaking in general terms, if test equipment that was purchased as NEW that came from a company that at some point ends up not being cooperative in disclosing service information about a product that is clearly serviceable outside of the factory, and with the exception perhaps of some custom parts can otherwise be repaired with common off the shelf supplies, this does not exactly foster and promote the desire in me to buy any further equipment of the same brand in the future when forced to replace any now unserviceable equipment because of their refusal or "inability". And let alone talk about recommending it to other peers. Again speaking in broad terms, I recognize that it is the manufacturers choice to withhold the service information, but ultimately it is my/our choice at large to continue buying and recommending that brand.


 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #9 on: September 15, 2019, 05:59:44 pm »
While a good quality DMM, 3.5 digit DMMs are usually not really serviced if there is something seriously wrong (e.g. more than fuse or battery contacts). So in this case no really important data missing.

You must be referring to factory service and then only "decent quality" series models, or those DVM-in-a-chip types. As for the HP972A-974A series they have lots of discrete thru-hole and SMD replaceable parts inside on the main board. And if it ever came to it (so far fortunately all my DVMs are working fine) it would be much easier to troubleshoot them if one had access to the schematic and possibly also to a parts layout diagram. So basically I have been looking for an schematic or service manual for this series mostly out of piece of mind and curiosity, as they are very well build and engineered for long term reliability unless the batteries are left inside for a long time without attention.
 

Offline CatalinaWOW

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #10 on: September 15, 2019, 06:00:48 pm »
I can't speak to how either of the companies involved made their decisions about document retention, but I have encountered a phenomenon that definitely affects publicly held companies in the US.  Product liability lawsuits are a real thing.  And deleting documents relative to a pending lawsuit is obstruction of justice.  So lawyers at some companies have recommended that ALL documentation be destroyed after a fixed period.  If the documents don't exist they can't be used against you, and if it is a general policy not aimed at a specific lawsuit it is difficult to prove that the intent is obstruction rather than just eliminating storage costs or other valid reason.  The recommended fixed interval varies but I have seen numbers ranging from 5 years to 25 years.

One more thing to thank our legal system for.  I am a firm subscriber to the observation that 99.3% of lawyers spoil it for the whole profession.
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #11 on: September 15, 2019, 07:25:36 pm »
Speaking of lawyers...

Another thing that I was wondering about is why did HP not disclose any technical information on these rebranded Yokogawa DMM series during the period when a lot of other documentation of older discontinued equipment was being made public by HP themselves. After all this was a product sold in the US with a HP badge. Maybe HP never even got to see schematics or service manuals at all, or they where only provided by Yokogawa with a convenient NDA in place.
 

Offline dseyst

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #12 on: September 15, 2019, 08:38:35 pm »
I have a 974a also. You can find a user/calibration manual at xdevs.com but I haven't been able to find the schematics yet. Yokogawa made a 7544 02 model which is very similar to the 974a. There is one 7544 02 for sale on ebay right now but the asking price is $199.
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #13 on: September 15, 2019, 10:02:14 pm »
Thanks for the input. However the user manual (or rather leaflet) that includes a very short calibration procedure is widely available from many other sources, if I remeber correctly even from HP themselves. But as you mention unfortunately not so for any service manual or even schematics, hence the reason for this post.

I tried searching on ebay for "yokogawa 7544" but nothing relevant came up, even by adding the last "02" to the model. Can you provide a link or ebay item number? Out of curiosity I would like to compare it with the 974A. The price you mention seems way out of line to the usual norm, should be more like between $50-100 and that is for the one with the HP badge, complete with yellow holster, test leads etc. I doubt that a Yokogawa even if in good shape "like new" condition will ever sell higher than the HP counterpart, and definitively not at that price level.

I have been monitoring ebay for 974A's for the better part of 4 years, passively as of late, as I do not think I will need to buy yet another one but always curious of what will come up next. On the other hand if something really nice out of the ordinary comes up like the last one in pristine like new never used condition in the original box with test leads and at the right price I could simply not pass on it, hence 974A #4. That one now sits in the closet as a back up unit, as I really don't have much more need or space on the bench for it besides the other four.
 

Online Kosmic

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #14 on: September 16, 2019, 01:04:38 am »
For reference, this is the Yokogawa 7544 02. Interesting that the accuracy is 0.04% and not 0.05% like the HP 974a. And the features (Averaging and etc) are not exactly the same.

« Last Edit: September 16, 2019, 02:23:36 am by Kosmic »
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #15 on: September 16, 2019, 02:37:44 am »
Where did you get this picture from? Its unfortunately very poor quality specially towards the top of the DVM.
From what I can make out it does not seem to be an exact equivalent of the 974A.
 

Online Kosmic

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #16 on: September 16, 2019, 02:54:23 am »
Where did you get this picture from? Its unfortunately very poor quality specially towards the top of the DVM.
From what I can make out it does not seem to be an exact equivalent of the 974A.

Google images. Found some pictures on a Japanese web site.
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #17 on: September 16, 2019, 03:08:30 am »
OK yes well as you mentioned the layout of the top buttons is definitively different than the 974A, so I doubt this is a direct equivalent. Good try though. Definitively close, but no cigar.
 

Offline dseyst

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #18 on: September 16, 2019, 03:12:37 am »
I just typed in ""yokogawa 7544 multimeter"" in the ebay search box a few minutes ago and the listing came up.
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #19 on: September 16, 2019, 03:22:24 am »
Link please?

Oh never mind finally found it.
https://www.ebay.com/itm/162986352332

I wonder if Yokogawa also included the yellow holster, not shown on the listing.
« Last Edit: September 16, 2019, 03:24:39 am by AMR Labs »
 

Online Kosmic

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #20 on: September 16, 2019, 03:26:41 am »
Don't think so. The yellow bumper on my 974a was made in the US. So was probably added by HP.
« Last Edit: September 16, 2019, 03:28:56 am by Kosmic »
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #21 on: September 16, 2019, 03:39:16 am »
Right you are. I'm now looking at one of mine:

Hewlett Packard
Boot Made in USA.

Beautiful bright yellow boot. Can't even get one of those anymore unless its on a Fluke.
They registered it as a trademark. Ridiculous this was even granted.
 

Online Kosmic

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #22 on: September 16, 2019, 03:50:49 am »
Beautiful bright yellow boot. Can't even get one of those anymore unless its on a Fluke.
They registered it as a trademark. Ridiculous this was even granted.

Haha didn't know that   :)
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #23 on: September 16, 2019, 04:28:30 am »
That is why you now see a lot of blue, red, black, and other colored boots. All except bright yellow. Only allowed now on Fluke DVMs.
Guess they had a good team of lawyers to win the case and be the only ones to be able to sport a yellow boot. Or maybe the counterpart's lawyers failed to make this valid point:

The yellow color of the protective boot is standardized to conform to industrial safety norms, and among others to make it easier to locate your instrument by sight. Its called "Safety Yellow" for a reason. Not meant to just look nicer, and Fluke claimed it to be "their proprietary image look". Its ridiculous that they where even allowed to claim exclusive use of the yellow boot. I would compare it to only a single company being able to manufacture bright yellow life vests, all others have to use some other less eye catching color. Guess which one will be more effective.
« Last Edit: September 18, 2019, 06:50:44 pm by AMR Labs »
 

Online artag

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #24 on: September 19, 2019, 08:21:25 pm »
My 970A multimeter is clearly marked 'Made in USA'.
 

Offline AMR Labs

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #25 on: September 19, 2019, 08:36:07 pm »
Your HP970A is a completely different DMM, its more like a hand-held probe type of instrument which was made by HP in the US.

No relation to the HP971A-974A series made in Japan by Yokogawa.
HP should have given the later multimeters a different model designation.
« Last Edit: September 19, 2019, 08:38:50 pm by AMR Labs »
 

Online artag

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Re: HP 973A & 974A Multimeter Service Manual anyone?
« Reply #26 on: September 22, 2019, 11:11:49 am »
It's also a little earlier .. 1973 :)
 


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