Datron 1271 Meter Repair Help - Page 1
Forum section: electronics / repair

author: latherton333
author_rank: Newbie
timestamp: November 30, 2011, 07:39:24 am
content: Hi. I'm Larry Atherton from Southern California.I am working on a couple of Datron 1271 meters. One of them has a faulty AC RMS board (option 12, high precision).Is there anyone that has experience in repairing these instruments? I need help interpreting an error code (2433, 1 V Offset), what it indicates, exactly, and what test paths are being evaluated that generate this the error (I think P063 and P064, but I'm not sure).Thanks in advance.Larry Atherton

author: amspire
author_rank: Super Contributor
timestamp: November 30, 2011, 08:14:35 am
content: I am not familiar with the meter, but the User manual is available:http://128.238.9.201/~kurt/manuals/manuals/Other/WAV%201271%20User.pdfIt does mention the error, but no real explanation. It is one of the tests for the 1VAC range.Richard

author: latherton333
author_rank: Newbie
timestamp: November 30, 2011, 11:50:59 pm
content: Thanks.I have all the manuals and the error is well documented. But even so, the error is mysterious to me. The output from the RMS board measures OK.Thanks.Larry Atherton

author: Bored@Work
author_rank: Super Contributor
timestamp: December 01, 2011, 06:53:30 am
content: I don't have the manuals, so just a suggestion: When the output is right, and the RMS measurement works, then why not consider that the self-test itself is at fault?Try to figure out how/what the self-test is measuring and if there is maybe something broken in the self-test measurement circuit.

author: latherton333
author_rank: Newbie
timestamp: December 04, 2011, 12:39:08 am
content: That the self-test circuitry, itself, is the cause of this error is a very insightful response.SIDE NOTE: For those out there that would like to understand this bug better, the 1271 multimeter runs hundreds of internal tests, and this meter passes all, except 2433. And this is actually NOT a measurement, but a digital calculation of the offset from other measurements that, themselves, all pass; it's a calculation using the output of the RMS converter from the application of +1 and -1 volts recorded during previous tests. The offsets from these tests are averaged and then compared to the Full Scale values; the result must be within +/- 100ppm. The measurements that the digital calculation uses (from Test Path P063 and P064; these I can inspect) are well UNDER the max 100ppm limit. So, that's the dilemma: The apparent source measurements pass...the values are within limits...but the digital calculation of the offset from Full Scale does not pass. It's kind of like saying: A=1 and B=1, yet A+B does not equal 2!BACK TO THE MAIN ISSUE: There is no way for me to determine what the 2433 digital calculation is actually measuring or calculating (other than relying on the printed Datron documentation for the specific measurement) without single stepping through the ROM code and reading what is being retrieved and stored in memory (not possible, for me, at least). So, to help eliminate the possibility of self-test errors being the cause of this problem, I have installed the RMS board in the second 1271 system I'm rebuilding. I get the same error (and only that error), so I can (maybe) eliminate everything BUT The RMS board.If one of the test-path relays on the RMS board was not working correctly (which MIGHT cause this type of error), it might corrupt the overall AC readings from the RMS board, which is not the case; AC measurements made with the 1271 compared to my calibrator output are actually OK on all ranges. So the error is likely not in the "meat" of the RMS board (the PreAmp, Rectifier, and RMS Converter). Which means that it STILL COULD BE a fault in the self-test circuitry on the RMS board, which I've examined very closely and tested. But I probably should go back and look at that, again.Thanks for the great suggestion.And thanks, again, for everyone that has provided feedback. All ideas are welcome!

author: attardeb
author_rank: Newbie
timestamp: April 20, 2012, 06:18:15 am
content: Dear Sir,This is with reference to the SELFCAL Digital multimeter 1271, Datron Wavetek. We are using above DMM from last so many years having no problem at all,But last two days back while checking DC CURRENT, There is one message displaying on the screen is "ERROR 0L". at the time of pressing DCI Function Key. And we are unable to solve this problem as well as our daily work has been stopped.We will be very thankful if you please guide us How to resolve this above mentioned problem.Waiting for your earliest reply?

author: ipmassey
author_rank: Newbie
timestamp: November 15, 2012, 10:00:23 am
content: I realise this is an old post but I have just spent two days with the same problem as Latherton333.Ensure that the DCV +1V and -1V measurements are correct as it uses this range to test for the offsets on the 1V AC range.It was only after reading your post that I realised I had not adjusted the negative values on the DCV ranges.Now it all passes!

author: quarks
author_rank: Frequent Contributor
timestamp: January 17, 2013, 10:59:04 am
content: Quote from: amspire on November 30, 2011, 08:14:35 amYesterday I bought this meter. It shows errors in the current function. Now I searched for documentation incl. error explanation list and saw this link. Butunfortunately the link does not work. Has anyone downloaded it and can share and is there even more documentation available?thxquarks

author: jnd
author_rank: Regular Contributor
timestamp: January 17, 2013, 02:22:52 pm
content: Quote from: quarks on January 17, 2013, 10:59:04 amI tried to google for WAV 1271 User.pdf and it came up with this:http://www.ntecusa.com/docs/WAV%201271%20User.pdf

author: quarks
author_rank: Frequent Contributor
timestamp: January 17, 2013, 03:04:06 pm
content: thx a lot,now I know for sure that the error code list is identical to the 1281 I already checked.All ranges show range gain magnitude errors. Has anyone had this before? Hints are welcome.Right now I check the involved OPAmp and the circuit around it.

author: quarks
author_rank: Frequent Contributor
timestamp: January 18, 2013, 11:35:47 am
content: does anyone have or can check for known good testpoint values of the Current Assembly (Option 30) board?

author: quarks
author_rank: Frequent Contributor
timestamp: January 18, 2013, 10:30:14 pm
content: I found a defect Diode type JPAD50 (D110 see picture), unfortunately this seems to not available at my usual shops anymore. Does anyone know of a possible substitute?

author: SeanB
author_rank: Super Contributor
timestamp: January 19, 2013, 06:04:48 am
content: Use a JFET and wire it so that it is a diode. All those are is a 30V JFET wired internally as one, used as they are very low leakage. BF545 or PMBFJ175 will probably work. First is n channel and second is p channel device, though the BF545 has a much lower gate leakage current of under 1nA and typically 0.5pA. Under a dollar each retail from RS.

author: quarks
author_rank: Frequent Contributor
timestamp: January 19, 2013, 08:57:21 am
content: Thx, that is a good idea.

author: MetraCollector
author_rank: Regular Contributor
timestamp: January 19, 2013, 09:01:07 am
content: Thank you very much for this hint, I have Grundig MO20 oscilloscope and when I bought it, it has deffective A-input with shot out JPAD20, I only desoldered it and now the scope is without protection.

author: quarks
author_rank: Frequent Contributor
timestamp: January 19, 2013, 01:41:08 pm
content: I pulled out the JPAD50 and tested it without replacement. Unfortunately, this was only part of the problem. But the Fast Test now shows less errors and the 100µA range is working. So I have known good values for the Testpoints. I now wonder what else can cause the "range gain magnitude" failure, because I assume that the OP amp must be ok. In the 100µA range the TP106, 105 and 102 are 0V as expected but in the other ranges it is -150mV (at 1mA), -15mV (at 10mA), -2mV (at 100mA) and -0.9mV (at 1A) . All other TPs are ok. Does anyone have an idea what to look for?

author: SeanB
author_rank: Super Contributor
timestamp: January 19, 2013, 01:55:07 pm
content: Sticking relays, failing Fets or the analogue gate driving them, or an open circuit resistor. Check D107/8 by substitution, they along with the fets may be leaky.

author: quarks
author_rank: Frequent Contributor
timestamp: January 19, 2013, 03:19:20 pm
content: @SeanBthx, for your help.I just edited my last input, because I had a typo and the suspicious TP values vary in the current ranges (I missed to point that out).The relays seem to work fine.About the D107, this one is in the working 100µA range, so think it should be fine. The D108 is in the 1mA range and the DG211 (M101) PIN16 is high, which means the switch (PIN14 to PIN15) is off, so Katode is at +15V. But the TP values are -150mV. Should leakage then not pull it up to positive values? Also in all other ranges (except 1mA) the PIN 16 is low and therefore the switch is ON which makes PIN14 -15V.

author: quarks
author_rank: Frequent Contributor
timestamp: January 22, 2013, 08:56:32 pm
content: After a few days off this topic, I tried again today.And now I found Q101 is the trouble maker. I pulled it out, now all ranges work except the 100µA.Now I have to find either U1899 (as listed in schematic) or a PN4093 (which I actually pulled out).Or maybe anyone has a suggestion, what could be a good replacement?BTW I found a source for JPAD50.When I have all parts replaced I hopefully have a error free working meter.thx to allquarks

author: quarks
author_rank: Frequent Contributor
timestamp: February 13, 2013, 09:11:02 pm
content: Just a final update. Today I received the long awaited last missing part. Now Full Test passed (see picture) and everthing works fine.thx a lot for all helpful repliesnext thing I will try is to implement the RATIO Option. Any hints are welcome.Quote from: quarks on February 08, 2013, 05:18:35 pm