EEVblog #613 - Prema 6047 Multimeter Teardown

[EEVblog]

Teardown Tuesday.
What's inside a 1980's vintage 8.5 digit multimeter, the 6047 from Prema. Or did Dave diddle himself?
Hi Res photos: http://www.eevblog.com/2014/05/07/eevblog-613-prema-6047-multimeter-teardown/

[quarks]

 Nice score, but not 8.5 digit
See the real ones here
https://www.eevblog.com/forum/testgear/8-5-digit-dmm/msg258880/#msg258880

[FrankBuss]

Reading the EPROM would be interesting. Sometimes there are hidden messages or easter eggs: http://www.lemon64.com/forum/viewtopic.php?t=49609

[gaijin]

The 100 milliohm shunt resistor was made by ISOTEK they have been around since 1989.

http://www.isotekcorp.com/

[senso]

That thing looks like it was used in the shop floor so all the new assemblers could try and melt some FR4, that or it was repaired by someone else, but it really doesn't seem to have the spit and polish of a precision bit of kit, more like a 6 month special kit from elektor 

[Vgkid]

That is a beautiful meter, and it arrived in good condition as well. Here is the manual W/ schematics
http://www.ko4bb.com/manuals/index.php?dir=09)_Misc_Test_Equipment/Prema

[david77]

Nice score Dave!

Love the SDS brand relays in there. That company used to be in my hometown, the factory is still there now owned by Matsushita/Panasonic. They're still making relays and industrial control gear there.

Btw. Isabellenütte is rather older than 25 years...
http://www.isabellenhuette.de/en/company/innovation-by-tradition/history/

[justanothercanuck]

Did you say 6502? 

I wonder what the ROM looks like.  Is there a ROM dump out there?

[TiN]

Lovely, volt-nuts will enjoy. Thanks for teardown.
Moar precision DMM content, please   

Is that ceramic resistor network Caddock 1737?

[SeanB]

Nice score Dave!

Love the SDS brand relays in there. That company used to be in my hometown, the factory is still there now owned by Matsushita/Panasonic. They're still making relays and industrial control gear there.

Btw. Isabellenütte is rather older than 25 years...
http://www.isabellenhuette.de/en/company/innovation-by-tradition/history/

Funny enough I had a faulty thermal resistor from them, had to replace it with an Omron H3B timer. 11 pin timer block, 11 pin base, mount on DIN rail and wire it up, all to replace a single 2 wire part. The Isabellenhutte thermistor was taking too long to heat up, and the part number ( thanks to Google translate) is now obsolete 40 years.

[Stonent]

I was surprised he didn't point out the HP chips on there. I didn't catch what they were, though.

[Huluvu]

Yeah -  FRAKO Electrolytic Capacitor around 18:10 

[Mickle T.]

Can't find a datasheet for HP R8200 optocoupler 

[Rasz]

I bet the 6048 is just one bit flip in dallas ram
6502 is trivial to reverse engineer

[poorchava]

Isabellenhütte produce shunt resistors and power resistors (up to several hundred watt) and roll their own resistive alloys. Great quality and stability too. I've seen some automotive qualification results (pretty stringent standards) and their standard range of products exceeded the pass criteria literally by orders of magnitude. Really good stuff

[sportq]

Although it was labelled as serial number 1040-something, I bet they started at 1000. HP did this, nobody wants serial number 0001 (except eevblog uC fans )

Pete

[wiss]

I bet the 6048 is just one bit flip in dallas ram
6502 is trivial to reverse engineer

Almost, substitute lm399 for ltz1000.
But same input-amp.

[opablo]

What's so special about Tellurium Copper ?

I just read the wikipedia article on Tellurium and didn't got what's so special about it for electronic connectors...

[robrenz]

IMO it is purely for the machinability ONLY.  It does nothing for electrical properties and is not as good as oxygen free copper electrically. If it was better electrically you would see it in spade lugs etc. but you don't. You will only see it used where the product is machined (turned milled etc.) not stamped like spade lugs. Telurium copper is readily available only in round stock further supporting my theory that it is purely for machinability.

[Zbig]

Koax!

[Dr. Frank]

Isabellenhütte produces very good low ohm shunt and power resistors.
See here: http://www.isabellenhuette.de/en/home/

I think the designation "Hütte" originates from the metallurgical "smelting" process. (I hope I have picked the correct English term.)
Obviously that's the historical root of this company.

In the famous old Ruhrgebiet, in Western Germany (Krupp, Thyssen, Mannesmann, etc.) they smelted the ordinary steel and iron alloys, but this company specialized in electrical alloys, obviously. Today, they still produce their own specialty alloys.

The brand "Zeranin" is a special or selected Manganin alloy, T.C. being <3ppm/K, or even <1ppm/K, instead of >= 10ppm/K for the elder Manganin.
High quality wire wound precision resistors are also made of Zeranin, and fully compete against the metal foil technology of Vishay.


What I have noticed, all PCBs were labelled 6048, therefore, probably a different assembly and a different EPROM may turn this instrument into a real volt-nuts 8 1/2 digits one.

Around the LM299, there's enough space for the LTZ1000 and its accompanying components.

But anyhow, if calibrated properly, even this version is capable of ~1ppm stability, especially after 25 years of ageing.
Therefore this instrument will definitely qualify Dave as a real volt-nuts.


Frank

(who initially created the term "voltnut")

[guido]

That blue philips cap is not original i think.

I have a prema 5000 (5 euro  ), which has similar parts like the relays and reference. But more prema specific ic's, it is a lot more integrated and smaller. But 6.5 digit only. Those board to board connectors are horrible. Mine has only one towards the display pcb and it took some tinkering to get it reliable. But in the 5000 the other board to board connectors are flatcables with connectors pressed into regular ic sockets     Did a full recap on mine, i use it a lot these days. Got it 'calibrated' at a real voltnut

The analog board:


Interestingly the 6502 clock is derived from the analog side (adc) and transported to the dig side with an opto. In your meter it is "free running".

Prema is very helpful if you mail them! They still support their meters. E.g. full calibration for your meter is 653 euro according to a pricelist i got last year. Calibration can probably be done via keys and gpib. They also still repair them, so i guess they have some of those prema chips available. They are also willing to answer technical questions via mail and send service manuals.

My guess is that the battery is flat. In the 5000 are three 2114 rams. One is battery backupped and its a cmos version where the others are not (everyone that had an Acorn Atom in the past knows how power hungry the regular versions are )

[rolycat]

IMO it is purely for the machinability ONLY.  It does nothing for electrical properties and is not as good as oxygen free copper electrically. If it was better electrically you would see it in spade lugs etc. but you don't. You will only see it used where the product is machined (turned milled etc.) not stamped like spade lugs. Telurium copper is readily available only in round stock further supporting my theory that it is purely for machinability.

I'm not sure it's the only reason - tellurium copper combines low thermal EMF with better corrosion resistance than pure copper.

[robrenz]

Show me a couple of NON machined mass produced electrical components made of Tellurium copper and I might alter my opinion

[Wytnucls]

The Tellurium Copper machinist never runs out of elbow room