Advantest R6581 8.5 digit DMM mini teardown/repair - Page 1
Forum section: electronics / general

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 14, 2016, 09:54:11 pm
content: Here's a mini teardown of the Godzilla of multimeters, the Advantest R6581 8.5 digit beast from Japan.It's basically a baby 3458A. The R6581 has auto cal and 2 source artefact calibration, basic 10VDC 1 year spec is 5ppm. From what I've seen it has 2-3 times worse noise and linearity than the 3458A...but it's 2-3 times cheaper on the used market. There's a good review and teardown from our friends at38hot, very interesting read.Mine has developed a fault on the current ranges, it seems that the 1000mA Range relay wants nothing more than to spend the rest of its life together with the 0.1Ohm shunt, it's latched on forever and ever. The unit is just about 18 years old now, can't say I'm surprised.Only a short teardown today, I just needed to know what relays to order and I'll be taking more pics during the repair.Not much screwing around was needed, 2 to take the covers off, 1 for the shield and 3 for the AC board.Above is the AC board, only the R6581 has this option, the R6581D/T models are DC only.The current shunts are on the upper right. Lots of nail polish and AE hermetic sealed resistors (?) dotted around the place.It's got an LTZ1000 reference, not the A version! Set to 65C methinks.That's it for now folks, I'm going to investigate if the relay is stuck on or if it's just under orders from above. I'll be replacing some of the electrolytics and relays while I'm at it. Sourcing them will probably take quite a while... oh boy.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: March 14, 2016, 10:07:46 pm
content: Thank you for the pics. Do you have any of the manuals? It seems information on this beauty is rather scarce.

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 14, 2016, 10:16:11 pm
content: Quote from: ManateeMafia on March 14, 2016, 10:07:46 pmI uploaded ithere, how's your Japanese?I've bugged Rohde & Schwarz to see if they can give me any more info, they're the Advantest distributors in Australia.

author: TiN
author_rank: Super Contributor
timestamp: March 15, 2016, 04:05:42 am
content: Moar pics, please! Can I steal them?Perhaps after repair you may like to participate in some comparisons for 8.5-league?Currently comparison pool likely to be is 6 x 3458A, 3 x 2002, 2 x 1281 and perhaps 7081.

author: quarks
author_rank: Frequent Contributor
timestamp: March 15, 2016, 06:50:12 am
content: Hello deadlylover,looking forward for more to come.I really like the R6581 because it has artifact calibration as the 3458A but a much more userfriendly UI.Thanks for sharingByequarks

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 15, 2016, 08:59:02 am
content: TiN,Yep you're free to steal all the pics, I will take much more when I remove the boards. ^^The orange relays are still made by Panasonic, DS2E-SL2-DC5V ($20) and S2EB-L2-5V ($6). Ouch.The silver ones marked UBT/UBM-12205 are made by Sanyu, I think they are shielded low thermal EMF reed relays. They're old part numbers and I've contacted them to help find a modern equivalent, they've probably just gone through a renaming scheme and I hope they weren't custom order by Advantest.The R6581 is a great meter, it is like the 2002 (dual line VFD) and 3458A had a baby. Even a dummy like me had no trouble at all using the meter the day I got it.They pop up every now and then on Yahoo Japan for about USD700-1000, still expensive but somewhat within reach of hobbyists. I think I need to acquire a few more to act as spares units, but I can't help but hold the funds for a used 3458A instead.... it still calls out to me...

author: chihaxinh
author_rank: Regular Contributor
timestamp: March 15, 2016, 02:09:53 pm
content: Using relay like 34401a , i dont see any reed relay and hope never have like 34401a !

author: Kleinstein
author_rank: Super Contributor
timestamp: March 15, 2016, 05:06:25 pm
content: The relays used for current range switching should not be that critical - high current, maybe reasonable low leakage, but no need for low EMF, very low leakage or high voltage. So chances are good to find suitable of the shelf ones.The metal cases around the reed relays is also there the reduce the driving power, it works as part of the magnetic circuit. This is nothing so unusual and expensive. Anyway I don't think these relays are used for the current ranges - more like voltage ranges and ohms.

author: AF6LJ
author_rank: Unknown
timestamp: March 15, 2016, 05:13:29 pm
content: This is just too cool, I love the hermetically sealed resistors.This is almost as good as RF Porn.

author: chihaxinh
author_rank: Regular Contributor
timestamp: March 16, 2016, 09:40:32 am
content: User manual Japanese language only! so if want to calibration process to hard!How to runing calibration dmm?

author: Gyro
author_rank: Super Contributor
timestamp: March 16, 2016, 10:02:25 am
content: Nice to see a piece of precision test gear that actually looks like it is, rather than some anonymous looking smt PCB. That AC board is a work of art!

author: lowimpedance
author_rank: Super Contributor
timestamp: March 16, 2016, 10:51:10 am
content: That is a nice bit of kit, Precision resistors by Alpha Electronics (Japanese naturally).The lack of readily available documentation (and nice internal pics) has stopped me acquiring some Advantest gear although I keep browsing them from time to time ....... so tempting

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 16, 2016, 01:07:48 pm
content: Quote from: chihaxinh on March 16, 2016, 09:40:32 amCalibration/adjustment is very easy, the manual is not needed!Menu > Calibration > ExternalWe can select 10VDC or 10k Ohms, all we have to do is apply a value to the meter's inputs and enter the applied value (anywhere from 9-11VDC/kOhms), job done!Then every 24hr or after a 1C change in ambient temperature, we can run the internal calibration. It takes about 15 minutes to run a full internal cal.Menu > Calibration > Internal > (All, DCV, Ohms, ACV)I just heard back from R&S that they will not service any units above 15 Years old, and that Advantest will not make any service documentation available, even in Japanese. Oh well, more fun for me then.Still awaiting a response from Sanyu, maybe I'll get one by the weekend, I should try the Japan office.

author: Theboel
author_rank: Frequent Contributor
timestamp: March 16, 2016, 01:31:49 pm
content: from the internal foto I really like this DMM very well lay out for example how they made the power supply shield, but why this this DMM "can not" beat 3458 ? any one has theory about why ? I like to hear it even the wildest oneFor deadlylover thank You Sir for pictures.

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 16, 2016, 01:51:53 pm
content: You're very welcome, more pics soon I promise!I think the 3458A's A/D converter is just too good.Here is a snippet from the R6581 brochure, on the left is the linearity error on 10VDC tested at a Josephson junction array and on the right is the zero noise.

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 16, 2016, 02:46:08 pm
content: Hi deadlylover,thanks for sharing .. and I wish you a lot of fun with this 8.5 measurement box..Do you have any idea, how the ACAL is done in this instrument?You know, many precise 10:1 transfers and several mode conversions from 10V and 10k are necessary..The 3458A uses its 0.02ppm (typ.) linear A/D (for ~0.3ppm transfer accuracy).. The Datron 1281 uses a precision ratio transformer.. for the 34465A / 470A, I do not know, yet.So, any hint inside the instrument? What can we learn from the specification of the other DCV ranges?How linear is the 6581, actually? The diagram looks very promising, also in the league of the 3458A, isn't it? Seems to have about 0.05..0.08ppm INL?Frank

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 16, 2016, 04:39:09 pm
content: Dr Frank, you're welcome, I was expecting you here sooner or later.I'm guessing that the R6581 also uses it's A/D converter, I may have read somewhere on the manual or brochure that it did it using "ratio", but that's all it said, I think it implies it uses the A/D. The only other hint from the specs is that the 24hr range error from 10V>1V>0.1V increases from 0.1>1>10 ppm of range.Hmmm now that you mention it, maybe I haven't given the R6581 enough credit. I thought that the 3458A easily had the upper hand because it had much less range error on DCV, but with a closer look I noticed that the 3458A spec also included having to use the MATH NULL function.If we include that extra error without using MATH NULL, the R6581 is identical to the 3458A when comparing 24hour specs....actually, the R6581 beats the 3458A on 10VDC (0.5+0.1 vs 0.5+0.2)....I think?Of course we don't know how the R6581 performs on a level playing field with MATH NULL, which we will always use when taking accurate measurements, but it seems Godzilla isn't going down without a fight!

author: quarks
author_rank: Frequent Contributor
timestamp: March 16, 2016, 04:40:11 pm
content: here is a DCV comparison chart I made quite a while ago (see att. pic.)R6581 is quite good, but not as linear as the unrivaled 3458A in the 10V range.As I have both 3458A and R6581 I must say again, the R6581 is a lot easier to use and I like it for that.3458A ACAL looks to me identical to R6581 "Internal Calibration".Biggest drawback, as mentioned several times before, is missing documentation/schematics.

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 16, 2016, 07:30:24 pm
content: DeadlyLover , Well yes,R6581 has the LTZ1000 implemented correctly, at 45°C, no wonder that it has 5ppm/yr. instead of 8ppm/yr., and so easily beating the 3458A in this aspect. (Could even be spec'ed much better, anyhow)The spec. reveals the ACAL function, as the ranges have constant difference in uncertainty, e.g. 1V for all times constantly 1ppm more uncertain than the 10V range.This 1ppm difference requires, that the 10:1 ratio transfer must have been made with an uncertainty of 0.1ppm of input. From the linearity curve you presented, that fits to the INL of 0.08ppm (of Range) for its A/D.The 100mV is always critical, due to thermal voltages; 10ppm is about 1µV, only.Often, you can not null these offsets in real measurement situations, so you have to include them in the spec.For example, if you measure a Weston standard cell, you can't short the DUT for cancellation, so you will at least measure all thermal voltages at the jacks, internally to the DUT, also on the cables.In my post about the 34465A/470A, also ACAL instruments, I later found out, how to verify 100mV DC on the '465A vs. the 3458A, more precisely.The trick was, to null both instruments at zero output of the calibrator, and then applying the 100mV or 1V.. The ratio of both readings gives the gain calibration for the '465A only, and these 10 or 15ppm additional error (due to thermals) is eliminated. After that procedure, the 100mV range (gain) was measured to be uncertain to < 1ppm.Maybe that's a specific advantage of ACAL instruments, as they also eliminate offsets during the ACAL procedure, so that external thermal offsets really can be nulled.Stability (24h, 2h, 10min) and noise measurements would also be interesting.Frank

author: Macbeth
author_rank: Super Contributor
timestamp: March 16, 2016, 09:31:50 pm
content: Quote from: deadlylover on March 14, 2016, 10:16:11 pmI ran it through a couple of hours of Adobe Acrobat OCR anduploaded ithere.(Strangely enough, page 584 appeared to already be OCR'd).So at least that allows one to cut-and-paste pages to translate.google.com or something like that.If I actually owned a R6581, I would take the next step and get in touch with an old friend who spent 6 years in Tokyo, fully translate the darn' manual and typeset it too! But so far the japanese yahoo auction site has them for even cheekier prices than a 3458A.Then again, I am happy with 6.5 digits. That's like the odd pint and maybe a bit of a toke now and then7.5 is probably adding a bit of speed and ecstasy on the weekend, but 8.5 is like hard drugs, heroin and krokodil injected in the groin because no veins left...

author: deadlylover
author_rank: Frequent Contributor
timestamp: March 16, 2016, 10:40:52 pm
content: Quote from: Macbeth on March 16, 2016, 09:31:50 pmThat might have been me.Cheeky prices indeed, the last few auction listings a couple of months ago went for about JPY80,000. You don't really see too many good deals that are buy-it-now on Yahoo Japan.Top tip for fellow volt nuts looking for one of these beauties, I've already mentioned this a few times but I might as well repeat it in this thread one last time. The R6581 has an internal battery that keeps the configuration memory, and the one on my unit pooped out on me after 16-ish years.When the battery dies the meter will show an error (config memory lost) only one single time after it initially loses its contents. The meter does a quick self test on power up and no error will show on subsequent power on cycles. Now, this memory also stores the internal calibration constants, and if it is missing, the meter won't show any readings because it auto-ranges like a madman with relays firing non-stop (making sellers think there's something seriously wrong with the unit). Running the internal cal will restore functionality until the next power cycle, and it will show the error one more time.The battery is a bog standard 3.6V axial leaded 1/2AA cell.So if you ever see a cheap listing with those symptoms...jump on it! You can bet there'll be quite a few units running out of batteries over the next few years.Oh and another thing, the R6581 has a real time clock inside and when an external calibration is performed it stores the date and time, so don't forget to pull the data over GPIB before calibrating!I forgot to do that and all I know is that my unit drifted about 9ppm/13ppm on 10VDC and 10KOhms (1.5ppm/1ppm 95% uncertainty respectively). There's a chance my unit has never been adjusted since the factory in 1998 but there's no way to be sure, I feel like I let all fellow volt-nuts down by forgetting to check that.

author: chihaxinh
author_rank: Regular Contributor
timestamp: March 18, 2016, 11:34:18 am
content: Hi deadlyloverWhere is location of battery ? repalace battery can lost calibration ?

author: z01z
author_rank: Regular Contributor
timestamp: November 30, 2016, 10:16:33 pm
content: Some pictures about theR13020 Analog output unit.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: September 02, 2017, 08:48:39 pm
content: If it's interesting, a R6581(D,T) have a full featured diagnostic mode, triggered by pressing HOME + POWER switch.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: September 05, 2017, 07:12:26 am
content: Also R6581 got a lot of improvements during its production. Some of my early research is here: