[volt-nuts] Solartron 7081 Test Leads

[Fred]

I have the 7061. You let yours on for twenty four hours. I do that with
my calibrators ect but I did it once with my solartron and I allmost had
a fire. It was over 30 degrees Celcius and the meter got so hot it
started smell burned. At 23 degrees, after about an hour my meter gets
towards 50 degrees insite. The transformer around 55 degrees.

Is this normal, is it made to be used in 20 degrees environments or is
there something wronng ? I have no service manual so I can not check
anything. I replaced the nicad, tested the powersupply caps but they
were OK. Could niot find a ripple on the psu that was abnormal (as far
as it is a guess without the manual)

It's to bad because it is a great working meter but as long as I do not
know if this is normal (not allowed to use above certain temps) I do not
use it much. 

The cal key locjk is plain standard but I tryed some old keys and after
some modifications it worked :-)

Fred

Bill Ezell schreef op do 04-08-2011 om 18:08 [-0400]:
> Joe, If you don't have a cal key, the switch form-factor is standard. I 
> just replaced the switch on my 7081. If I remember correctly, the part 
> number isn't the same, but the mfgr is. I ordered from Digikey.
> 
> Who did you order the Fischer connectors from? I tracked down part 
> numbers a few years ago, but couldn't find anyone to actually sell them 
> to me. I found one at a flea market, and I did snag two original cables.
> 
> Regarding the cables/probes, there were several models. The most common 
> have two banana plugs. The connection thru the cable is true 4-wire, 
> terminating at the plug. There was also a version with 5 plugs (4-wire 
> plus shield), and a version with a pair of Kelvin clips (the real ones, 
> one of each pair to each side of the clip).
> 
> You don't need a Kelvin connection for anything other than resistance 
> measurement. The meter does quite well with the 2-plug version for that 
> anyway.
> 
> I used 5-wire + shield PTFE / pure copper (picked up on EBay, lots of 
> mil-spec cable shows up there, mostly from aerospace leftovers) 
> terminated with Pomona low-emf plugs.
> 
> BTW, these are really great meters (except for the read time at 8.5 
> digits!). Mine keeps cal within typically 1 or 2 ppm for over a year at 
> a time. Yes, seriously. I compare it periodically to my 
> (Fluke-calibrated) pair of Datron 4910 references, and almost never have 
> to recal. (Another wonderful piece of equipment, the 4910).
> Nice thing about all these old pieces of equipment, they're usually well 
> down the aging curve. :)
> 
> One thing, they really take 24 hours to fully stabilize, so let it run a 
> few days if you're going to calibrate it.
> Have you checked out the voltage ref it uses? Amazing.It's just a 
> non-ovenized Zener, albeit one that was designed to be a ref (the 
> still-available 1N829A). The Zener itself is good to about 5ppm/C. 
> Solartron then calibrated each one to find the inflection point on its 
> voltage/temp curve. The meter has a DAC that sets the current to be at 
> that point. Then, they add a non-linear temperature-dependent 
> compensation voltage to eliminate even more tempco. If you look at the 
> Chinese meter review referred to by other posters, you can see how it 
> compares to the HP. Pretty impressive.
> 
> One more thing, read your cal constants! The critical one is the Zener 
> bias setting. If you lose the EEPROM, that one would be very difficult 
> to determine again. The rest can be recovered by a recal.
> 
> On 08/04/2011 01:13 PM, volt-nuts-request at febo.com wrote:
> > Solartron 7081 Test Leads...
>