Datron Autocal 1061 (Fixed - Thank You for all the help) - Page 1
Forum section: electronics / repair

author: Laszlo
author_rank: Contributor
timestamp: April 06, 2019, 08:17:41 pm
content: Hi, I've recently won a Datron multimeter on fleebay, surprisingly it powers up, and it is in a really good general condition inside an out. When the self-test is initiated it cycles through the screen but flags up an error 6 message (Resistance measurement self-test failure). Everything else is fine. It measures DC, AC, and current with no probs.I have managed to select the resistance measurement option on the front, but it just measures a short circuit, irrespective of what I have connected to the end of the probes.I had a look through the forum regarding the other Datron repair topics but I am still a bit lost. Many of you guys had recommended replacing the caps on the analog board so that is where I started the fault finding and noticed that on the some of the blue axial caps have a nice square wave input and most of them have nothing. Tried enabling multiple modes to see if they come alive, but no success.Also had a look at the ohms board, but couldn't see anything blatantly obvious. It really is in great shape, no dust no corrosion, no bulging caps.Any input is much appreciated.Below images are for the signals I captured with the scope with reference to the multimeters ground.1st is on the first and second cap.2nd is the 3rd cap and above. They are all the same no input what so ever.

author: wn1fju
author_rank: Frequent Contributor
timestamp: April 06, 2019, 09:14:18 pm
content: I always look at the mechanical stuff first. For instance, there is a relay on the ohms board. See if it is being driven and if it makes good contact whenit closes. There may also be problems with relays that route signal paths if there is a rear-panel option (although this is less likely given that you saidyour meter reads DCV and ACV correctly).Otherwise, there are generally no shortcuts other than to download the service manual and start marching through the schematics. Good luck.

author: tggzzz
author_rank: Super Contributor
timestamp: April 06, 2019, 09:54:49 pm
content: The other shortcut is to google to see if anyone has solved a similar problem.Old optocouplers have reduced current transfer ratios, and sometimes replacing them solves marginal behaviour.IIRC the Datron has some binned optocouplers, delineated by coloured paint spots.

author: Laszlo
author_rank: Contributor
timestamp: April 06, 2019, 10:05:37 pm
content: I haven't actually checked the relay on the ohms board. It does an audible click when the Kohms range selected. And I assumed that its a happy duckThe relays at the back look as brand new. But then again, pretty much everything looks like brand new in that thing.The only reason I started checking the caps because everybody else has reported them being faulty. Nevertheless, will be the relay first thing I'll check. Thanks for the input!I've seen those optocouplers but didn't dare to touch them. I've read in here that they can't be easily replaced as they were hand selected by grey bearded virgins.

author: maginnovision
author_rank: Super Contributor
timestamp: April 06, 2019, 10:31:27 pm
content: I'd probably start by trying to reseat the connectors and a visual of the ohms board and the analog board. Some people might disagree but I think you're pretty safe to reseat all the analog board IC's, and the ohms board as well. Caps are more preventative than anything. If it works it works but the caps are very old if they've never been replaced and you have no idea the conditions the thing operated in previously by replacing them you can be relatively sure they won't be a problem.The 6 caps at the front of the analog board are for the input filter I believe. If nothing seems to help you may just want to look at the ohms board calibration in the service manual to check what you get compared to what you should.

author: DC1MC
author_rank: Super Contributor
timestamp: April 06, 2019, 10:35:03 pm
content: The caps on the analogue board are done, replace them. They don't die like other caps, bulging and spitting corrosive fluid (thanks God), they just lose capacity and increase the ESR.For the resistance measurements first make sure that the front switch it's in 2W(ire) position, not 4 W(ires), this usually makes the self-test fail, but decreases the price of used Datrons, so I won't complain.Also during self test make sure that you don't have anything connected to the measurement terminals, especially metal straps between the posts.Cheers,DC1MC

author: DC1MC
author_rank: Super Contributor
timestamp: April 06, 2019, 10:39:29 pm
content: @maginnovision: The 6 elco caps are part of a voltage multiplier for the analogue isolator part of the analog board. Nobody will ever put elcos in an input filter for a measurement deviceCheers,DC1MC

author: maginnovision
author_rank: Super Contributor
timestamp: April 06, 2019, 10:44:44 pm
content: Quote from: DC1MC on April 06, 2019, 10:39:29 pmSorry, I'm pretty tired.Quote from: DC1MC on April 06, 2019, 10:35:03 pmI don't know where his came from but I now have 4 1062 and 1 1072 and all of the analog board al-electros were good, all from the west coast of the USA. I still replaced them but none of them seemed to have any issues according to the der ee de-5000.

author: dacman
author_rank: Frequent Contributor
timestamp: April 07, 2019, 02:27:34 am
content: If C45-C50 on the analog PCB are not Philips (and light blue), they have been replaced. OEM: 10 uF 63 V, 33 uF 40 V, 47 uF 25 V, all 6 x 10 mm. I've replaced lots of these capacitors with a violet bluish looking capacitor (made by BC Components which is part of Vishay) that are the same size as OEM but got a voltage bump (10 uF 100 V, 33 uF 63 V, 47 uF 40 V). I later started using CDE 6 x 16 mm capacitors (black and gray).Testing these capacitors in parallel mode will generally identify a bad one (although I like to also measure D and R). If measured in series mode, then ESR or D will also need to be tested.

author: gearshredder
author_rank: Contributor
timestamp: April 07, 2019, 05:40:02 pm
content: I wish I had the current option..

author: Laszlo
author_rank: Contributor
timestamp: April 07, 2019, 06:46:25 pm
content: I've ordered the capacitors, so I should be able to report back by the end of next week.BTW where do you usually order the components from? I've looked at RS, and ebay but couldn't find reasonable prices. I ended uppaying 5 pounds for 25 axial caps. Never even looked at the tantalums as they were prohibitively expensive.Surely there must be a way of finding them cheap.Quote from: gearshredder on April 07, 2019, 05:40:02 pmIf you are based in the Uk, you might have some luck here; (trade only)https://www.ppauctions.com/lot.php?l_id=126653&id=250&search=datron&cat=all&perPage=20&sort=2&thisPage=1Also, the reason I manage to get one for cheap because the seller was selling it asdaytron, which is not its correct nameYou might have the same luck if you are searching a bit.

author: tggzzz
author_rank: Super Contributor
timestamp: April 07, 2019, 07:06:15 pm
content: Quote from: Laszlo on April 07, 2019, 06:46:25 pmFarnell is another UK alternativve, CPC has some cheap tant beads.Digikey isn't a bad alternative either.

author: Testtech
author_rank: Regular Contributor
timestamp: April 10, 2019, 04:07:48 pm
content: For self test to pass the front panel switch must be set to 2W.

author: Laszlo
author_rank: Contributor
timestamp: April 13, 2019, 07:44:26 pm
content: Hi,I've changed the axial elco's, and some of the dodgy looking tantalums on the analog and ohms board. Now the display powers up really quick, and selects the DC mode 1000V range as default. - GreatBut it does nothing else. Self-test fails on error 6. When the ohms board removed it fails on error 8 or 7.Before I changed the caps it measured DC voltage fine. Now it seems like the inputs are not working anymore. I've double checked the polarities on the new caps, nothing out of the ordinary. I've also checked (tried at least) whether I can measure anything on the test points at the ohms board and apart of one test point none of the others are showing any sign of signal.I am starting to think that there is some issue with the input perhaps. Reading through the manual it should check the inputs when it goes through its self-testing sequence. Perhaps there is something wrong in there.It is my first repair attempt, any kind of input is much appreciated.

author: Testtech
author_rank: Regular Contributor
timestamp: April 13, 2019, 09:35:35 pm
content: As I recall, if you remove the ohms board you must install a jumper in place of the ohms input connector.Usually when working on a problematic Datron, I disconnect all the optional boards; ohms, current, AC, jumpering as required.Then, starting with a DC only instrument, it is much easier to get that working properly first, then add the options and troubleshoot those as required.

author: Laszlo
author_rank: Contributor
timestamp: April 13, 2019, 10:29:23 pm
content: I know it will sound stupid..Where do I need to fit the jumper? Could not find anything in the manual about it..https://archive.org/stream/datron_Datron_1061_1061a_1062_Service_Manual_complete_with_schematics_and_partlist/Datron_1061_1061a_1062_Service_Manual_complete_with_schematics_and_partlist_djvu.txt

author: dacman
author_rank: Frequent Contributor
timestamp: April 14, 2019, 01:51:12 am
content: For Error 6, test the input circuit resistance (which I would do while it is powered up). I would first suspect the relays.Self-Test flips the Front/Rear relays to the Front. There are two connectors on the rear backplane on the left side that come from the Front/Rear relay board. The one with two wires switch the V+ and I+ terminals and come from the 2-Pole relay. The one with four wires switch the V-, I-, V-Guard, and Ohms-Guard circuits and come from the 4-Pole relay. Pull these two connectors from the backplane, move the 2-Wire/4-Wire switch to 4-Wire and the Guard switch to Remote for testing purposes, set the Front/Rear switch to Front, and test the resistance of V+, V-, I+, I-, V-Guard, and Ohms-Guard from the front panel to the connectors (which will also test the relays). If the resistance is over 2 Ohms, then the relays need to be replaced or burnished.I would also test the Ohms PCB relay. The pins that need to be jumpered with the Ohms PCB removed are shorted out by the Ohms PCB brown connector when the Ohms function is not selected.During Self-Test, the 2-Wire/4-Wire switch needs to be set to 2-Wire and it also needs to be good or it can cause Error 6, so measure across it also.For Error 7, make sure the Remote/Local Guard switch is set to Local.

author: maginnovision
author_rank: Super Contributor
timestamp: April 14, 2019, 05:24:23 am
content: Quote from: dacman on April 14, 2019, 01:51:12 amWould you happen to know what to look at for commonly failing Lin calibration(Error 4)? One of my units fails 19/20 times. After calibration it appears to be accurate but I'd rather it not fail Linearity.

author: Laszlo
author_rank: Contributor
timestamp: April 14, 2019, 04:50:09 pm
content: Quote from: dacman on April 14, 2019, 01:51:12 amThe humble switch indeed. It does not switch in any position at all. Tried measuring across the contacts, and nothing. Those pesky mechanical components...Now I just need to mine it out from the panel.Thanks a lot!

author: dacman
author_rank: Frequent Contributor
timestamp: April 15, 2019, 03:21:49 am
content: I replaced that switch on a unit a few years ago. I got it from Digi-Key using the part number on the switch.As far as Lin Cal goes, if the power supplies are good (including the 42V Inverter), and the relays are good, (and the ICs are making good contact in their sockets), then try the hardware alignment by clearing the calibration constants and performing the Analog PCB hardware adjustments. There are three zero adjustments at the beginning of the Analog PCB hardware alignment. If you're getting Error 4 during Lin Cal, the unit has too large of an offset.There are some mistakes in the manual (but this may depend on which manual you are using). One is that TP13 in step 18 of the hardware alignment for the Analog PCB should be TP19. (TP19 is near R108 and R109.) Also, in step 28, TP5 should be TP3.

author: maginnovision
author_rank: Super Contributor
timestamp: April 15, 2019, 06:26:28 am
content: Quote from: dacman on April 15, 2019, 03:21:49 amThanks, I'll re-check the zeros and make sure supplies still look good. They were all good when I did it last but there was a note in the unit when I got it saying they suspected R160 of being faulty so I'll check to see it hasn't moved. I'll also make sure I check the manual against those TP to make sure everything was done right.

author: Testtech
author_rank: Regular Contributor
timestamp: April 16, 2019, 11:10:26 pm
content: The jumper goes in place of the input connector to the ohms board. This connects the front panel input through to the main board, bypassing the relay on the ohms board. Jumper pins 1&5.

author: Harbyshep
author_rank: Newbie
timestamp: April 18, 2019, 06:47:00 pm
content: Can anyone help me with the rear external inputs? The connector is stated as Pye M75 - a 7 pin male connector. Is there a modern compatible cable socket to mate with these connectors - I wish to make up some test leads and wish to use the rear input.Thanks

author: DC1MC
author_rank: Super Contributor
timestamp: April 18, 2019, 07:02:05 pm
content: Quote from: Harbyshep on April 18, 2019, 06:47:00 pmThe connectors are Pye M7P, if you want the original tryhttps://www.winconn.com/wp-content/uploads/2015/12/rp.pdfpage 76I think they are the only ones that may have them,Cheers,DC1MC

author: Laszlo
author_rank: Contributor
timestamp: April 19, 2019, 07:33:35 pm
content: Well, now it measures AC and Dc voltage. Ohms are still playing up, once a resistor is placed in between Hi&Low terminals it reads 1mOhms, irrespective of what is the value of the resistor.Had a look at the relay, but on my version, I've got two relays as opposed to the one which is on the drawing I've got. The coil resistance is the same what is written on it. However, there is only 14.5Vdc on the terminals. Not sure whether that is adequate, as per drawing it should be 15Vdc. - Could that be an inadequate power supply?So far I have changed the following parts;All the analog board electrolytic axial capacitorsFront panel 2/4 wire switchThe 10uf 350V axial capacitor on the power supplyFew tantalums because they were discoloredRegarding the current mode, It is just an open circuit on both modes. I suspect the relay on that one, it even passes the self test..

author: Gyro
author_rank: Super Contributor
timestamp: April 19, 2019, 08:34:03 pm
content: QuoteThat's not a problem, most relays close at about 2/3 of rated voltage. The missing 0.5V is probably the drop across the switching transistor.

author: dacman
author_rank: Frequent Contributor
timestamp: April 20, 2019, 09:05:26 pm
content: The relays are actuated by pulsing about 28 Vdc across the relays (for about 10 to 30 ms) then the positive section drops and the relays are held in by the negative supply. There is about 14.5 Vdc on the coil, vice 15 Vdc, because of a diode that completes the hold-in circuit.Test the coil voltage while switching the relay and make sure it is being pulsed to 28 Vdc.Measure the current path to the front/rear terminals. The Ohms PCB is a current generator.Measure contact resistance across the relays. (I do this by using the schematic and testing at connected parts.)24V SDS Relay: Actuates at 16.8 Vdc min; Held in by 2.4 Vdc min.

author: dacman
author_rank: Frequent Contributor
timestamp: April 21, 2019, 02:27:40 am
content: Your symptoms are as if the current path is open. Check the current fuse. Even Ohms I+ goes through the current fuse if fitted. (Without the current option, a link is used vice a fuse.)

author: maginnovision
author_rank: Super Contributor
timestamp: April 26, 2019, 12:06:28 am
content: Are thre ±8V rails critical for Lin Cal? The drop across the diodes is almost 4 volts and the 11V rail is ok which results in ±7V instead ±8. It's literally the only issue I've found on the problem unit.

author: Laszlo
author_rank: Contributor
timestamp: April 26, 2019, 07:35:52 pm
content: Hi,Finally, I had the time to take it apart again and checked the fuse the second time. Unfortunately, it was okayI assumed that if one switch was failing, there might be more mechanical issues along the current path from the front to the rear input relay assembly.The I+ rings out all the way to the current board, I- does not when I/dc selected.Therefore, I took the relay board out and did some fault finding.In my understanding (might be wrong), those relays should operate from +15V dc so thought - yeah let's test it on the bench. Hooked it up to 15V dc, nothing, a slight bodge at most. Increased the voltage to 24Vdc and it clicked. But it still does not work on 15Vdc..Is there anything special about these relays? I can't seem to find anything when I googled the part number.Cheers,Laz

author: dacman
author_rank: Frequent Contributor
timestamp: April 27, 2019, 02:10:27 am
content: For the Front/Rear relay board, it takes +/- 15 Vdc to run the relays along with the 0V common of the 15 Vdc supplies. When the Front/Rear switch is set to Front, Q1 and Q6 are turned on which applies -15 Vdc to the coils of RL1 and RL2. This -15V is also applied to C1 on the side which was near zero volts. The other side of C1 was near +15V but gets shifted down to near 0. This turns on Q3 which applies +15 Vdc to the other side of the coils of RL1 and RL2, and the 30V differential across the coils is enough to energize the relays. (The +15 Vdc from Q3 also reverse biases D3.) When C1 charges enough to cut off Q3, the relays remain energized through D3 which is now forward biased by the -15 Vdc supply through Q6/Q1 and the coils of RL1/RL2. When the Front/Rear switch is set to Rear, Q1 and Q6 are turned off and the bottom of C1 is discharged to near zero through the coil of RL2 and D3.Relays that can replace those are R10-E1P2-S3.2K, R10-E1P4-S1.8K, AZ420-V50-40LUS, and AZ421-V05-10LUS. These relays have 18V pull-in ratings. Relays with 21 V pull-in ratings can also be used.

author: dacman
author_rank: Frequent Contributor
timestamp: April 27, 2019, 02:56:48 am
content: Quote from: maginnovision on April 26, 2019, 12:06:28 amDo you have a thermal imaging camera? Check C25 and make sure it isn't leaking. The 8V rails power some of the CMOS and optoisolator ICs. Try swapping ICs with another unit. Also, if the analog board is placed in another unit does the problem move with it?

author: maginnovision
author_rank: Super Contributor
timestamp: April 27, 2019, 05:32:27 am
content: No thermal camera. Fault moves with analog board. C25 is a new kemet 20V part though and I selected lowest leakage part(hence the 20V rating). This is also a 1071 analog board.One thing I had to do for this board the others didn't need was adjust R11/R15 for step 26 of analog board adjustments. Originally there was a resistor in R11 spot and I had to remove it and put one in R15. Are these pick what works or do I need specific value? My TP9 reading is .1mV so the reading is within spec. I'll try swapping some ICs that use those rails.Checking against a good unit I found the "8V" rail is also unstable. Need to find out if it's the zeners breaking down or something else causing it. Hopefully it's related.I found out it's caused by an LED on the analog board. I can't find the LED in the schematics or board layout so I'm not sure why it's there but it seems to be original. No IC swapping has helped yet.EDIT: I've finally got back to this, replaced C9(Digikey P/N: 1572-1352-ND) and C12(Digikey P/N: 399-13034-ND. This is a PPS which are typically direct replacements for PC.) on analog board and it passes linearity calibration step fine.

author: Laszlo
author_rank: Contributor
timestamp: April 28, 2019, 11:23:45 am
content: Fixed!It was the 3rd relay at the rear module. Took it apart, cleaned the contacts and now it works like a charm on all 4 modes. No problem with the accuracy either when I checked it against my calibrated Metrahit multi-meter. Thanks for everyone who helped along the way, I would not have been able to do this without you.For anyone who had similar error 6 on these meters here is what I had done to rectify the issue;Replaced all axial electrolytic capacitors on the PSU and analog board. (They were all dried out without exception)Replaced some Tantalums on the Ohms and Analog board.Rung out the input all the way to the relays.Found 2/4 wire switch broken (replaced it).Found relay No3 at the rear not making contactRemoved relay 3 and 4 and cleaned both.Re seated and cleaned Ohm's board IC'sRe seated all connectors in generaly

author: tggzzz
author_rank: Super Contributor
timestamp: April 28, 2019, 12:00:09 pm
content: If only everybody listened, understood, had success, reported and summarised their success.Good for you!

author: maginnovision
author_rank: Super Contributor
timestamp: April 28, 2019, 03:57:40 pm
content: No Datron repair is a success without a PASS screenshot! Good job getting it fixed thanks for the summary.

author: Laszlo
author_rank: Contributor
timestamp: April 28, 2019, 09:58:31 pm
content: True.I've done another self-test again to show off with my screenshot and I've got my beloved error message again.But it still measures everything spot-on. I is well confused now.I've also noticed when I first turn it on, the resistance measurements aren't stabilizing, this issue disappears after the instrument was on for like 10 minutes.It can't be a mechanical fault surely since it measures. Could it be that its calibration is drifted away, hence the error?Cheers,Laz