Author Topic: Solartron 7061 7.5 Digits Multimeter Teardown and Repair  (Read 12418 times)

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Offline KosmicTopic starter

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #25 on: May 24, 2019, 04:00:18 am »
I really like the 7061. The one I repaired seem to be really accurate. It's not the kind of meter you use daily on your bench but for precision stuff, it's working pretty well.

The only problem is the connector. Not a problem anymore in my case  ;)

Need to finish repairing the second unit now.
 

Offline kblue

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #26 on: July 01, 2024, 04:05:45 pm »
Old topic, i know ... just don't want to create something new.

I too now own a 7061 and i like it. What was your exact replacement for the Schaffner Filter? Just a new Schaffner? Are these XLR sockets the "mini XLR" variant?
My meter seems a tad out compared to my trusty 2024 calibrated (company did the cal) Fluke :D A 10,00000 source reports as 10,000244 +/- with the 7061 and 10,00001 +/- with my Fluke. The manuals show how to "calibrate" the meter (digital i guess) but it seems, i need to do that for every range. The readings so far seem to be stable, just not as "accurate" as it could. Mayhaps its something else, i wasnt able to check the insides yet.

Oh, and the Ni-MH battery is replaceable anytime? Or does the meter need to be powered on? Some devices do lose the cal if powered of and battery removed.

Best wishes!
 

Offline KosmicTopic starter

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #27 on: August 12, 2024, 09:29:39 pm »
What was your exact replacement for the Schaffner Filter? Just a new Schaffner?

The Schaffner FN372-2/21 is still avaialble. https://www.mouser.com/ProductDetail/Schaffner/FN372-2-21?qs=62ecY7oL%252BWNQsCxHqtpJ8A%3D%3D

Are these XLR sockets the "mini XLR" variant?

I ended up going back to the original fischer connector since I found some original test leads. I don't recommand using any cheap XLR connector as I did.

An alternative to the fischer connector would be good quality standard 4mm banana binding posts https://www.eevblog.com/forum/repair/repair-of-solartron-7081-sn718/msg4031680/#msg4031680.

Oh, and the Ni-MH battery is replaceable anytime? Or does the meter need to be powered on? Some devices do lose the cal if powered of and battery removed.

You can replace the battery when powered off since calibration is stored on non volatile ram.
« Last Edit: August 12, 2024, 09:32:38 pm by Kosmic »
 
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Offline unseenninja

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #28 on: August 13, 2024, 07:54:06 am »
i wasnt able to check the insides yet.

Oh, and the Ni-MH battery is replaceable anytime? Or does the meter need to be powered on? Some devices do lose the cal if powered of and battery removed.

Check the insides as soon as you can. You will most likely find the battery leaking. The original battery would have been a NiCD battery. Replacing it with a NiMH is a really bad idea as they don't like being trickle charged and will leak even more badly than a NiCD. Here's the mess that I had to clean up on one of my 7061 meters:









The board needed to be cleaned with vinegar to start with to neutralise the alkali which had leaked from the battery. Then all the solder resist needs to be scraped off as the alkali finds its way under the solder resist and spreads even further. I replaced the battery with a supercapacitor. It easily lasts three months before it runs out of power. All the replacement parts need soldering on both the top and bottom of the board as the plated through holes get destroyed by the leaking electrolyte as well.
 
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Offline factory

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #29 on: August 13, 2024, 10:43:19 am »
Are these XLR sockets the "mini XLR" variant?

I ended up going back to the original fischer connector since I found some original test leads. I don't recommand using any cheap XLR connector as I did.

An alternative to the fischer connector would be good quality standard 4mm banana binding posts https://www.eevblog.com/forum/repair/repair-of-solartron-7081-sn718/msg4031680/#msg4031680.


The original Fischer connectors should still be available, but with a minimum order to obtain;
https://www.eevblog.com/forum/buysellwanted/group-buy-fischer-connector-plug-s104-a053-130/

There are lower cost clones of the Fischer connectors;
https://www.eevblog.com/forum/metrology/solartron-7081-reference-circuit/msg5580701/#msg5580701
https://groups.io/g/Solartron_Schlumberger_Equipment/topic/input_connector_cable/103448605

David
 
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Offline kblue

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #30 on: August 26, 2024, 11:32:17 pm »
Thanks for the reply. I ordered some new parts (including a supercap, same as in the picture unseenninja.

The only thing "missing" would be the calibration-key or another solution. The meter seems a bit out. 10.00000 VDC input with my fluke 8506a (recently back from calibration) shows 10.0004X (x is fluctuating a bit). Mayhaps it's because of bad testleads, as i am still waiting for the proper input-jack and stuff i ordered.

Calibration seems straight forward with this meter. As far as i understand the manual, all "VDC" ranges need to be calibrated separately? The example in the manual is about the "10 VDC" range.

Apart from that, i do love the blue digits. Even though, replacement of this VFD could be a problem in the future.

Best wishes!
 

Offline kblue

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #31 on: December 03, 2024, 09:26:55 am »
Still looking for a key-replacements or another solution like ... known pin-layout what connections needs to be shorted/open for Cal/NonCal-Mode.

Thanks in advance!
 

Offline factory

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #32 on: December 03, 2024, 05:25:40 pm »
There must be someone nearer to you, that could take a cal key to a cutting shop & get a copy made, I thought they all used the same type?

Edit: someone is already selling copies on ePay;
https://www.ebay.de/itm/255643980121

David
« Last Edit: December 03, 2024, 05:34:06 pm by factory »
 
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Offline unseenninja

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #33 on: December 04, 2024, 08:17:22 pm »
I can vouch for the keys from that seller. They work in all Solartron meters of that time, including the 7061.
 
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Offline Kurets

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #34 on: December 05, 2024, 06:01:11 am »
I have hand filed a key and can provide a drawing for you if you like. I also have two key blanks that I could provide if you are in Europe. Maybe I could file the key for you, but I am getting ready to move house so I don't know that I'll have the time anytime soon.

Edit: I see that you are in Berlin. I think that I bought my key blanks from Germany, so I will look this up and get back to the thread with more info.
« Last Edit: December 05, 2024, 06:03:37 am by Kurets »
 
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Offline Kurets

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #35 on: December 05, 2024, 07:54:56 pm »
The key blank I used was a Silca RO21, this is available from Ebay and is a profile/length match to the one used originally by Solartron. The attached picture shows measurements on a picture of a genuine key. I used only the measurements from the picture along with the paint+try method for checking interference in the actual lock. In the end I got a working key within about 1-2hrs of elbow grease.

I could not find my spare blanks today, but this link has some in stock in Germany:

https://www.ebay.co.uk/itm/254721466397
 
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Offline factory

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #36 on: December 05, 2024, 08:24:47 pm »
There seem to be some switch keys available online as "Ronis 601 switch key", that look very similar to the key I have, no idea how close they actually are.  :-//

David
 
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Offline unseenninja

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #37 on: December 05, 2024, 10:28:16 pm »
There seem to be some switch keys available online as "Ronis 601 switch key", that look very similar to the key I have, no idea how close they actually are.  :-//

David

I think all these keys are identical. Given the very clear pictures here, Kurets' measurements and identification of the exact blank needed, I'd say the bottom just fell out of the eBay seller's market. A set of needle files, a blank and a caliper is all that's needed to create one of these keys.

I've picked these locks before and they take about ten seconds with a simple rake, so it's not as if the key requires micron tolerances.
 
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Offline Kurets

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #38 on: December 06, 2024, 09:47:43 am »
Indeed, the key is low tolerance and the profile of the blank is very common. This site lists more alternative part numbers for the key blank: https://www.aldridgesecurity.co.uk/silca-1697-silca-ro21-to-suit-ronis.html and depending on your country one or another may be more available.

When I was making my key I actually had the turning direction of the lock wrong for a while, so I very much over-filed mine but it still works well. So as long as you have patience, and maybe one spare blank in case you make a mistake, there should be no reason to not have a cal-key  :D. I added a picture of my DIY key, which is clearly not quite the same as the genuine key.
 
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Offline kblue

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #39 on: December 06, 2024, 02:09:54 pm »
Thanks for all the input! Ordered some keys (-:

The final step would be to find someone here in GER to do a alignment + cal. I know my unit is a bit out of spec with a single known source (measured with a 3458A). Sadly every ... single ... range ... needs to be aligned separately.
 

Offline Kurets

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #40 on: December 09, 2024, 11:47:04 am »
To hijack the thread a little. My unit has a NiMH battery fitted, replaced 2017 according to a sticker on the unit. I see that there is quite some corrosion which I have tried to clean up with vinegar, but did not clean-off the soldermask etc.

I am thinking of installing a supercap like described above, but I was also thinking that an alternative option would be to install a lithium cell and and replace R501 with an LTC4054 set to low charging current (50mA or so). I guess changing one battery for another would have the same problem in the end? But wouldn't a supercap also be a leakage risk? I don't know the relative nastiness of the different solvents used.
 

Offline coromonadalix

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #41 on: December 09, 2024, 12:44:24 pm »
supercap would not be a problem if you respect it's operating voltages ... 

ok  we did saw some leaked ones in the past, never saw on modern ones ...

the higher capacity it as,  the longer it needs to be charged ...




 
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Offline unseenninja

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Re: Solartron 7061 7.5 Digits Multimeter Teardown and Repair
« Reply #42 on: December 11, 2024, 02:57:08 pm »
To hijack the thread a little. My unit has a NiMH battery fitted, replaced 2017 according to a sticker on the unit. I see that there is quite some corrosion which I have tried to clean up with vinegar, but did not clean-off the soldermask etc.

That may come back and bite you. As I said, the battery electrolyte seeps under the resist and keeps on spreading. I first used some dilute spirit vinegar, then lots of water and finally isopropyl alcohol.

As the supercap I used is rated at 5.5V, way above the nominal battery voltage, there's very little chance it will leak.
 


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