Test Equipment Anonymous (TEA) group therapy thread

[factory]

It was indeed used for testing electricty meters. It's from the Itron closure, so whatever what was left of that branch of Schlumberger is now probably gone. Can't find a manual for it yet, though...

Did it come with any cables/probes? Guess Itron filed all the paperwork in the bin.

It's surprizing how few results google can find, it completely failed to find this one, guess time to find a different web search engine, google no longer fit for purpose. 

https://www.eevblog.com/forum/metrology/sm7050-reference-standard-meter/

There was a mention of a teardown in that thread, but not seen it, if it's on here.

Another here, last used by EDF, incorrectly titled as SN7050;

https://esconce2014.estelenerg.org/10-les-outils-du-controle-electrique/9-1-compteurs-etalons-autres-appareils/comment-page-1/

David

[factory]

A package arrived from Digikey yesterday. A pack of EE2-4.5TNU relays (Dual coil latching in SMD package) and a long fine cranked tip for the Metcal.
Time to replace the relays on the Advantest / ADCMT 7461A DMM.
First issue is the correct relay is EE2-4.5TNUN. This is a "reduced footprint" version. Basically the dit of the leg in contact with the PCB is shorter. Thery re not a stock item but the EE2-4.5TNU is. Easily sorted out with a small pair of flush cutters. IT does show how tight the mounting of these relays is.
Removal of old relays was by cutting the legs with my smallest pair of lindstrom side cutters. Cleaned up the pads and soldered on the new relays.
And it works. 

However this thng is a pig to work on. The plastic parts have become brittle (date codes in IC's indicate it is no more than 20 years old) and break at the slightest touch and there is no technical information available.
I won't be buying another one.

NUN seems to be an option from NEC, seems Kemet/Yageo no longer produce it and they have elimated any reference to it the current datasheet.
There were other brands making these telecom type relays, just can't remember them at the moment.

Did you take any pictures when you had the DMM open for repairs?

David

[factory]

...
Someone has really messed with those display boards, the '5MHz' 05232-6010 board is in the wrong place, it should be next to the 5245L-4B.
Also check the numbering on the chassis, as both A15 & A16 sometimes both can be 5MHz boards, this varies depending on the BCD code option. 

Those early silicon transistors are a bit fragile, they seem to give far more trouble than the Ge ones.

Not surprized to see yet another open circuit 1500uF 15V capacitor (C10), from experience this exact type often fails open in the 524xL/M counter range and the 412A voltmeter, the other types have been fine in all the counters I have.

David

Thanks for the heads-up, changing the position of the 05232-6010 board became first on the to-do list; it saves me from potential headache, beside, it acts up: stuck on 1, but resets to 0.
Situation of C10: see attached picture; it get replaced with a blue Phillips ...

Is a Philips (only one 'L') part really worse than an open circuit 50+ year old cap? Can't tell from the picture but it could be from the rebrand to BC, Vishay eventually canned the transparent blue sleeving.

This RS rebrand of Hunts/Erie/ITT in the 5248M probably needs to go, I've got a box of NOS axial RIFA PEG 1500uF at 25V, one of which got temporarily fitted to the 5245L, this got the H18 option fitted, still haven't got the top/bottom covers to complete this counter.
And I re-stuffed one can cap in the 412A and fitted one underneath in the 412AR.

David

[44kgk1lkf6u]

Finally got around to backing up the two drives. I didn't need Pocket Linux to get the SSD data; I just connected my USB to IDE adapter to it directly and I used dd to copy over all the contents. I think you should be able to do it this way if you run Linux on your computer.

The amplifier appears to be an ASIC (U3500 and 3600).

Thank you.

It is not fun when you open a thing to find out how it works only to find that it uses unobtainum.

The things in orange look like a capacitor and 2 ferrite beads.  Does anyone know what they are called?

Interesting choice of coax connectors.  The first time I came across one of those in an oscilloscope, I did not know the cable could be unplugged.  I ordered the electronic connector book by Andrea.  Hopefully I will not have those misunderstandings any more once I read the book.

[EggertEnjoyer123]

The things in orange look like a capacitor and 2 ferrite beads.  Does anyone know what they are called?

They're PI filters

[PascalNE]

A slightly sad story today, I bought a solartron 7075 7.5 digit multimeter sold as "mostly working" unfortunately something must've happened (not the sellers fault it was packaged very well) and now is presenting complete giberish.
It did come with the sought after GPIB manual and the nice original cable and certainly looked to be in good condition.
Due to the  complex nature of the instrument and the slightly scary floating circuits I think I'll have to sell it on for someone else to have a go at fixing, it's certainly above my current skill level.
I could sell it in bits but it feels wrong to strip apart an instrument that was working only a week ago. 

[wkb]

Put on the nitril rubber gloves, fetch you anti-static wrist strap and start reseating and wiggling connectors and boards. Maybe IC's in sockets too.

My bet is that something came loose due to vibration.

Wilko
'Who Dares Wins'

[PascalNE]

That is good point there is a whole lot of important looking socketed ICs. I already reseated some of the connectors but I wasn't brave enough to dig to the second layer of PCBs.

[wkb]

It probably is something in the digital section, so I would stay away from sensitive analog voodoo for now.

[tggzzz]

A slightly sad story today, I bought a solartron 7075 7.5 digit multimeter sold as "mostly working" unfortunately something must've happened (not the sellers fault it was packaged very well) and now is presenting complete giberish.
It did come with the sought after GPIB manual and the nice original cable and certainly looked to be in good condition.
Due to the  complex nature of the instrument and the slightly scary floating circuits I think I'll have to sell it on for someone else to have a go at fixing, it's certainly above my current skill level.
I could sell it in bits but it feels wrong to strip apart an instrument that was working only a week ago. 

Do the basics: test the PSU voltages and ripple, wiggle the connectors, repeatedly use the switches.

Make sure it is in local control, not remote.

If it is a PSU problem, the PSU is a single board at the back, and can be removed without fiddling with the rest of the unit.

The interboard connectors are pretty horrible: 14/16 way ribbon cables going to IC sockets. Wiggle the IDC headers at each end.

There's an excellent manual available now https://bama.edebris.com/manuals/solartron/7075/

[PascalNE]

Yes, perhaps I was too hasty I'll definitely open it back up tomorrow. In terms of testing the voltages the manual insists an isolation transformer must be used when doing any servicing will it be possible to test the voltages safely without one?
In case anyone has any ideas what could cause an issue like this these are the results of the self test.
1. Expected = 7.000v Displayed  = -87.868
2.Expected = 0.000v Displayed  = -80.868
3. Expected = 10.000v Displayed  = 80.818
4. Expected = 10.000kohm Displayed = 80.878kohms

When an external voltage is applied I get these results-
0v -> -0.808...
1v -> 0.818...
2v -> -0.828...
5v -> -0.858...
10v -> -0.808..
12v -> -0.828...

So as you can see from this the 3rd digit is somehow correct?? To me this definitely feels like a digital problem but I really dont know.

[DavideAndrea]

>  I ordered the electronic connector book by Andrea.

Thank you! Let  us know what you think when you get it.

[TheDefpom]

The 7075 isn't that scary, I've got one here which I recapped the power supply on, did a video or 2 about it, I even found a cheaper and similar connector to replace the original one so I could make a test lead, mine had dirty inter-board connections too.

[AVGresponding]

They are surprisingly impact resistant, as I'm sure tggzzz can testify...

(yes, it's still in GWO and only just retired since the arrival of the 7071)   

[AVGresponding]

Yes, perhaps I was too hasty I'll definitely open it back up tomorrow. In terms of testing the voltages the manual insists an isolation transformer must be used when doing any servicing will it be possible to test the voltages safely without one?
In case anyone has any ideas what could cause an issue like this these are the results of the self test.
1. Expected = 7.000v Displayed  = -87.868
2.Expected = 0.000v Displayed  = -80.868
3. Expected = 10.000v Displayed  = 80.818
4. Expected = 10.000kohm Displayed = 80.878kohms

When an external voltage is applied I get these results-
0v -> -0.808...
1v -> 0.818...
2v -> -0.828...
5v -> -0.858...
10v -> -0.808..
12v -> -0.828...

So as you can see from this the 3rd digit is somehow correct?? To me this definitely feels like a digital problem but I really dont know.

It is interesting how many 8's are displayed. I would suspect something in the display driver. Bear in mind these displays run at around 160VDC and strike at 180VDC or thereabouts, though at very low currents.

Sorry to be doing the red caps thing but it bears repeating:


ISOLATION TRANSFORMERS DO NOT MAKE VOLTAGES SAFE, THEY JUST MAY LIMIT THE CURRENT YOU MIGHT EAT, AND GIVE YOU ONE EXTRA CHANCE NOT TO BE THE CURRENT PATH. NOTHING CAN REPLACE GOOD WORKING PRACTICE.

THEY REMOVE THE PROTECTION YOU MIGHT HAVE FROM AN RCD/GFCI


One hand behind your back while you probe, connect before you energise the circuit when you can, remove metal jewelry/watches first. Wear gloves, and don't work when you're tired.

[PascalNE]

Could be the display driver but I think there is definitely deeper issues. I'll have another go at extracting some data over GPIB but the interface didn't seem to want to do it last time.
And in terms of safety I think I'll just do what I normally do and always connect to the circuit when it's not live.
I'll try reseating everything this morning if that doesn't work I have to wait a couple days till I can get in my bench and test it properly but we'll see then 

[tggzzz]

They are surprisingly impact resistant, as I'm sure tggzzz can testify...

(yes, it's still in GWO and only just retired since the arrival of the 7071)   

For transport, it helps if you have a custom-made wooden box

Good to hear "GWO"

[factory]

The large wooden box makes no difference to faults being created by shipping, mine arrived with the LSB of the display disabled & would only show even numbers, reseating the connector for the display PCB is all that was needed to correct the problem.
The display is multiplexed using just two HV display driver/decoder ICs and six 2N5401 transistors to select the digits.

A slightly sad story today, I bought a solartron 7075 7.5 digit multimeter sold as "mostly working" unfortunately something must've happened (not the sellers fault it was packaged very well) and now is presenting complete giberish.
It did come with the sought after GPIB manual and the nice original cable and certainly looked to be in good condition.
Due to the  complex nature of the instrument and the slightly scary floating circuits I think I'll have to sell it on for someone else to have a go at fixing, it's certainly above my current skill level.
I could sell it in bits but it feels wrong to strip apart an instrument that was working only a week ago. 

Selling working instruments in bits is what 'MJ' does, try not to copy them, it pisses me off no end, knowing they parted out some rare TE and stuff where I was the second highest bidder.
It would bother me slightly less it they didn't take the piss with the asking prices on parts, often one part is more the what it sold for complete & working.

David

[tggzzz]

The large wooden box makes no difference to faults being created by shipping, mine arrived with the LSB of the display disabled & would only show even numbers, reseating the connector for the display PCB is all that was needed to correct the problem.

David

I did wonder whether the lack of impact-absorbing foam/rubber would matter. Good that you fixed it so easily.

[PascalNE]

Reseated all the easily accessible connectors but I need to take the front panel off to get to the display connectors so I'll try that at some point. I also tested some of the rails and they all were on point.
But even if there is a display issue and it can be fixed I think the sickness runs a bit deeper and probably more work than I'm willing to put in.

Selling working instruments in bits is what 'MJ' does, try not to copy them, it pisses me off no end, knowing they parted out some rare TE and stuff where I was the second highest bidder.
It would bother me slightly less it they didn't take the piss with the asking prices on parts, often one part is more the what it sold for complete & working.

But don't worry I'll sell it all in one piece maybe selling the cable separately though and the GPIB interface since someone might want those for their fully working 7075. 

So if anyone is interested in a 7075 you can make an offer although I'll probably put it on Ebay/FS section next week.

[madao]

7075 repair is a bit difficult.

Mine 7075 has also fail in Display (it looks like, 2 of BCD code is stucks high. )  and i found bad TTL Multiplexer.
I have check with heating by heat-gun ->  since heating to ~70-80C° works multiplexer fine, up today.

It happens few years ago.  I got two 7075 with 70755 GPIB Module,  both is dead, doesn't respond. -> i have make 7075-UART Interface .
https://github.com/matt1187/7075UART

Back to topics.
My HAMradio-find HP 4270A is electric in very good condition.

[Zoli]

Is a Philips (only one 'L') part really worse than an open circuit 50+ year old cap? Can't tell from the picture but it could be from the rebrand to BC, Vishay eventually canned the transparent blue sleeving.
...

David

Here's the capacitor; I cannot identify the brand. Is 25V/85°C rated; measured 1970µF/ESR=0.025Ω. It works, but it will get exchanged to a 1.5mF/105°C/10khour one.

[factory]

It's BC Components, the rebranding of Philips resistors/capacitors from Jan 1999, now of course part of Vishay (since Dec 2002).

https://www.vishay.com/en/company/brands/bccomponents/

David

[factory]

Reseated all the easily accessible connectors but I need to take the front panel off to get to the display connectors so I'll try that at some point. I also tested some of the rails and they all were on point.
But even if there is a display issue and it can be fixed I think the sickness runs a bit deeper and probably more work than I'm willing to put in.

Selling working instruments in bits is what 'MJ' does, try not to copy them, it pisses me off no end, knowing they parted out some rare TE and stuff where I was the second highest bidder.
It would bother me slightly less it they didn't take the piss with the asking prices on parts, often one part is more the what it sold for complete & working.

But don't worry I'll sell it all in one piece maybe selling the cable separately though and the GPIB interface since someone might want those for their fully working 7075. 

So if anyone is interested in a 7075 you can make an offer although I'll probably put it on Ebay/FS section next week.

Even if you sell the DVM, it may be worth hanging on to the lead, as it's used for a few other DVM/DMM from Solartron.

For the display fault, have a look at the display driver ICs, there are two DD700 used for cathode drivers, the ones stuck at '8' will be driven by the same DD700, these do fail along with the DS8880 equivalent. The DI 258 is used to select pairs of anodes, this one seems to be working fine, as you are getting some correct digits displayed in-between the '8's.
Relevant parts of the circuit diagram attached below.

David

[tggzzz]

... there are two DD700 used for cathode drivers, the ones stuck at '8' will be driven by the same DD700, these do fail along with the DS8880 equivalent. The DI 258 is used to select pair of anodes, this one seems to be working fine, as you are getting some correct digits displayed in-between the '8's. I can probably help if you need a DD700 equivalent.
Relevant parts of the circuit diagram attached below.

And look at all those lovely SK* sockets just waiting to be jiggled and deoxidised