Solartron 7061 eeprom help and some photos

[muvideo]

Hello, recently I added to my collection a beautiful solartron 7061 multimeter.
The meter seem to function correctly but the low price I paid is justified by some problems.
The problems are that the unit seem to be far off calibration, some of the measurements it
shows are wrong by half a percent.
I turned the calibration key and entered the cal menu and soon the unit started showing the
"cal not done" message, i returned in normal position without proceeding into calibration routine.
Now it shows "cal not done" after startup and "CALO" text aside the measurement.

Is there anybody that knows this instrument?
I have operating manual that includes cal procedure but it would be nice if somebody has or
can tell where to find a service manual.

It has a 3.6V nicd battery that is dead, i desoldered it and cleaned the area that started
corroding, i read somewhere that the ram powered by this memory contains  only power
clock and measurement data.
There is also a seeq DQ2816a EEPROM that I suspect contains cal costants.
I tried to start the meter without the EEPROM ant it's behaviour is the same than
with it, so I suspect the 2816 is failed and this justifies the scrapping of the meter
by the original owner.


I think it's time to for me search for a cheap all-round eprom programmer, any
suggestion is welcome

Fabio.

Following the  photos that show the instrument, the memories, the battery,
the reference area and some canned components marked vishay 0.01%
that should be resistors.
The reference is built around a 1N829 zener diode, I didn't expect a
"simple" zener as reference for such a resolution but I think the knew what they
done.

[tekfan]

Congrats on your purchase. That's one nice meter!

The EEPROM is programmed by the multimeter when you go trough the calibration procedure. So you don't need an external programmer. You may want to try and calibrate it first before buying new ICs. You've got nothing to screw up because it isn't calibrated anyway.

And don't forget to replace the battery before you try to calibrate it. Even if it is just for power clock and measurment data.

[muvideo]

Congrats on your purchase. That's one nice meter!

The EEPROM is programmed by the multimeter when you go trough the calibration procedure. So you don't need an external programmer. You may want to try and calibrate it first before buying new ICs. You've got nothing to screw up because it isn't calibrated anyway.

And don't forget to replace the battery before you try to calibrate it. Even if it is just for power clock and measurment data.

Thank you for congratulations
I understand the fact that the multimeter stores the calibration in eeprom, the programme will be
used to backup all the roms for future and in case anybody needs them.
Also I'm curious to understand if this eeprom is faulty or corrupted.
I think sometime in the past it was calibrated, after something happened and it is no longer calibrated, so
I imagine some eeprom location become corrupted or all the eeprom is faulty.
Now I dont' have all the necessary to carry out a full calibration so I'll search first all info.

One person on volt-nuts mailing lists says that the instrument could not mantain the calibrations
with a faulty battery, so I'll replace the battery first, after I'll backup the eeprom and check if
it is functioning.

Fabio.

[MetraCollector]

Hello Fabio

This is a really beautyfull multimeter. I like it. Where did you buy it ?
Thanks for the photos.

It is a pitty that you lost calibration, but I believe you will manage to restore this unit.
But I have a question. Is it explicitly written in the manual that EEPROM stores calibration ? What is RAM chip+memory battery used for ?

I am asking according to my M1T380 multimeter which was made by Metra in 80s and I really feel that they copied topology of multimeters from western world and this Solartron is no exception.
In M1T380 there is a SRAM chip backed-up by memory lithium-battery and this chip stores calibration.
The software is stored in EPROMs.

But if you say that the EEPROM chip is bad, it is worth than replacing it.

Good luck, regards Ondrej

[muvideo]

Hello Fabio

This is a really beautyfull multimeter. I like it. Where did you buy it ?
Thanks for the photos.

Hello Ondrej, I simply found it on an ebay auction.
I started searching for a good used multimeter, I started
reading around and comparing specs, I realized that
these solartron and the datrons are really beautiful
instruments so I started to behave like a collector

It is a pitty that you lost calibration, but I believe you will manage to restore this unit.
But I have a question. Is it explicitly written in the manual that EEPROM stores calibration ? What is RAM chip+memory battery used for ?

I am asking according to my M1T380 multimeter which was made by Metra in 80s and I really feel that they copied topology of multimeters from western world and this Solartron is no exception.
In M1T380 there is a SRAM chip backed-up by memory lithium-battery and this chip stores calibration.
The software is stored in EPROMs.

Yes, it's a pity for calibration, probably I'll not be able to calibrate it anywere near what it is
capable of. The fact that cal constants are stored in the EEPROM comes from some messages
I found on volt-nuts mailing list archive, also is a deduction from the fact that the ni-cd backup
battery probably is unable to be reliable because of self discharge. Also the presence of
an EEPROM and the calibration procedure that involves two steps:
- calibrate, check if it is good and
- refresh that stores the constants.
I dont' know if the EEPROM is faulty it's gust an hypotesis.
Another problem will be the connector that I dont' have (by the way I don't have the
key but I learned that I can be a thief, or the key is particularly simple, because it easly
tampered with a flat blade   )

But if you say that the EEPROM chip is bad, it is worth than replacing it.

Good luck, regards Ondrej

Thank you Ondrej,
I read with taste your messages and the photos that you posted.

Fabio.

P.S.
I haven't yet found the original instrument that brought me into this collection,
but I choose to search for a keithley 2015 for some needs I have, when I'll find one
used in good conditions (and reasonable calibration state) i'll buy one.

[Richard W.]

Very nice voltmeter, especially the blue display looks very fancy 
I hope you can bring it back to life.

The reference is built around a 1N829 zener diode, I didn't expect a
"simple" zener as reference for such a resolution but I think the knew what they
done.

Its datasheet says 0.0005%/K temperature coefficient. thats 5ppm/K.
A LM399 has 1ppm/K and a LTZ1000 has 0.05ppm/K

[alm]

I wouldn't be surprised if there was another form of temperature compensation, like other components with an opposite tempco. This is what Datron did for their high-end meters: two diodes with opposing temperature coefficients in series, and several of these strings in parallel.

[sorenkir]

Hello Fabio,

Did you try to download Service Manual for Solartron 7081 there: http://www.ko4bb.com/manuals/index.php?dir=09)_Misc_Test_Equipment/Solartron
This is not the same instrument but it is of the same vintage and may share some maintenance procedures...

I own myself a 7065 (6 1/2 digits), much older, without any calibration memory. All data is stored in 'mechanical' memories: potentiometers !

Regards,
Michel.

[muvideo]

Hello Fabio,

Did you try to download Service Manual for Solartron 7081 there: http://www.ko4bb.com/manuals/index.php?dir=09)_Misc_Test_Equipment/Solartron
This is not the same instrument but it is of the same vintage and may share some maintenance procedures...

I own myself a 7065 (6 1/2 digits), much older, without any calibration memory. All data is stored in 'mechanical' memories: potentiometers !

Regards,
Michel.

Hello Michel, I didn't think of it, I'll download and check if these is any similarity, only I read somewhere that
the 7081 has to be interfaced trough serial terminal to proceed to calibration.
(Wondeful beast the 7081, 8 1/2 digits and very high specs).
Is there any service documentation available for 7065?
I'm interested because I have also a 7060 with all-pot calibration and found no documentation,
but I followed the service manual of 7045/7055 and it seems that many schematics/procedures
are similar, maybe the 7065 is very similar to 7060.
I can post an image of analogue board so we can figure if they are similar.

Very nice voltmeter, especially the blue display looks very fancy 
I hope you can bring it back to life.

The reference is built around a 1N829 zener diode, I didn't expect a
"simple" zener as reference for such a resolution but I think the knew what they
done.

Its datasheet says 0.0005%/K temperature coefficient. thats 5ppm/K.
A LM399 has 1ppm/K and a LTZ1000 has 0.05ppm/K

I hope too, it seems in very good shape, only I want indagate why
he lost the calibration.
Like said alm I think too that there is a form of compensation for the
entire reference circuit, it also makes something in firmware,
the manual states that in ohm the instrument performs "drift correction"
every 15 minutes, it can be disabled in menu, but also in voltage mode
 periodically (some minutes) you can ear the reed relays making
some switching and after the display jumps some digits.
Fabio.

[sorenkir]

Hello,

Service Manual for 7055/7065 is on Bama : http://bama.edebris.com/manuals/solartron/7055

You can also find interesting information about these meters in the first pages of the Solartron 1987 Catalogue available there after registration:
https://www.testmart.com/advice/mfgcatalogtmp.cfm

A lot of US patents related to A/D conversion and voltage references are held by The Solartron Electronic Group:
3617885, 3745556, 3942172, 3943506, 3976896, 4340883, etc.

Regarding voltage reference used in these meters
7065 : DC precision 0.0005% -> ovenized zener USR932 (5ppm/°C)
7055 : DC precision 0.002%  -> zener IN939A (5ppm/°C)

I have attached a  picture of the ovenized zener in the 7065, in fact a very small "oven"!

Regards,
Michel.

[muvideo]

Hello,

Service Manual for 7055/7065 is on Bama : http://bama.edebris.com/manuals/solartron/7055

You can also find interesting information about these meters in the first pages of the Solartron 1987 Catalogue available there after registration:
https://www.testmart.com/advice/mfgcatalogtmp.cfm

A lot of US patents related to A/D conversion and voltage references are held by The Solartron Electronic Group:
3617885, 3745556, 3942172, 3943506, 3976896, 4340883, etc.

Regarding voltage reference used in these meters
7065 : DC precision 0.0005% -> ovenized zener USR932 (5ppm/°C)
7055 : DC precision 0.002%  -> zener IN939A (5ppm/°C)

I have attached a  picture of the ovenized zener in the 7065, in fact a very small "oven"!

Regards,
Michel.

Thank you for all info, I remembered wrong before, for the 7060 I followed exactly the
service manual you linked, checking the schematics the 7060 seems just like a 7055 with an
extra digit of resolution. Exellent specs for the 7065 and interesting the ovenized zener,
strangely seems that the DC input impedance of solartrons multimeters has gone lower
 from older to newer ones:

10V
7075 <20pA and >1Tohm (10s integration)
7065 <20pA and >100Gohm
7061 <50pA and >10Gohm

Fabio.