Solartron 7061 7.5 Digits Multimeter Teardown and Repair

[Kosmic]

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.

[kblue]

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 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!

[Kosmic]

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.

[unseenninja]

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.

[factory]

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

[kblue]

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!