Datron Autocal 1061 (Fixed - Thank You for all the help)

[Laszlo]

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.

[wn1fju]

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 when
it 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 said
your 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.

[tggzzz]

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.

[Laszlo]

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 duck 
The 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.

[maginnovision]

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.

[DC1MC]

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

[DC1MC]

@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 device 

 Cheers,
 DC1MC

[maginnovision]

@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 device 

 Cheers,
 DC1MC

Sorry, I'm pretty tired.

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.

I 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.

[dacman]

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.

[gearshredder]

I wish I had the current option..

[Laszlo]

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 up
paying 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.

I wish I had the current option..

If 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=1

Also, the reason I manage to get one for cheap because the seller was selling it as daytron, which is not its correct name You might have the same luck if you are searching a bit.

[tggzzz]

BTW where do you usually order the components from? I've looked at RS, and ebay but couldn't find reasonable prices. I ended up
paying 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.

Farnell is another UK alternativve, CPC has some cheap tant beads.

Digikey isn't a bad alternative either.

[Testtech]

For self test to pass the front panel switch must be set to 2W.

[Laszlo]

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. - Great

But 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.

[Testtech]

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.

[Laszlo]

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

[dacman]

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.

[maginnovision]

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.

Would 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.

[Laszlo]

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.

The 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!

[dacman]

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.

[maginnovision]

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.

Thanks, 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.

[Testtech]

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.

[Harbyshep]

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

[DC1MC]

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

The connectors are Pye M7P, if you want the original try
https://www.winconn.com/wp-content/uploads/2015/12/rp.pdf page 76

I think they are the only ones that may have them,

 Cheers,
 DC1MC

[Laszlo]

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 capacitors
• Front panel 2/4 wire switch
• The 10uf 350V axial capacitor on the power supply
• Few tantalums because they were discolored

Regarding 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..