Dave, What is the problem with the original reference? I have not heard of too many failing. There was also a reply from Hank on another message. Perhaps he can provide the needed parts from a 732A?
Todd On Mon, Sep 14, 2015 at 6:45 PM, Dave M <dgmin...@mediacombb.net> wrote: > After making a mess in my garage while searching for it, it turns out that > that my Fluke is a 731B. It appears to use the same Voltage Reference IC > as the 731A, so no big deal there. > I found a previous discussion about the 731/732 reference ICs. Seems that > the ICs are either from Motorola (MCA1914/MCA1924/MCA1934) or GE (RA3). > Doubtful that GE continued production of that IC very long, so my guess is > that these are Motorola parts. It's all moot, since none of the parts are > still in production. I'm afraid to contact Fluke for a quote on the > IC/Resistor set. Don't think my heart could stand the shock. > > I'd really like to get this unit back in operation, but I don't want to > break my bank account to do it. I have a few LM399s on the shelf, so I > guess that will be my best approach to a repair. > > Thanks for the discussion, > Dave M > > > > > M K wrote: > >> On 12/09/2015 23:12, Dave M wrote: >> >>> I realize that better references are available. >>> >>> I was thinking of resurrecting a long-defunct Fluke 731 that I have >>> in the garage. The reference IC is bad in it, and (1) I don't want >>> to throw it away without a meager attempt at repair, and (2) I don't >>> want to spend a lot of money on it because it's in pretty bad >>> physical condition. >>> >>> I was hoping that someone could lend a touch of advice on those old >>> references. I have a few 1N827A reference zeners, and a washtubful >>> of transistors. Maybe something could be cobbled together that >>> would get the 731 back in operation. Maybe not to original specs, >>> but close, which is better than nothing. >>> >>> Thanks for your reply, >>> Dave M >>> >>> >>> >>> Jack Mcmullen via volt-nuts wrote: >>> >>>> Just thinking why would you reinvent a transistor/zener reference >>>> when the industry's voltage reference chips are in the $2.00 or less >>>> single quanities with performance far exceeding anything previously >>>> available in discrete components?? >>>> >>>> >>>> >>>> >>>> -----Original Message----- >>>> From: Dave M <dgmin...@mediacombb.net> >>>> To: FEBO Volt-Nuts <volt-nuts@febo.com> >>>> Sent: Sat, Sep 12, 2015 1:58 pm >>>> Subject: [volt-nuts] Making a Reference IC >>>> >>>> >>>> >>>> >>>> I was looking at the schematics for the Fluke 731 and 732 voltage >>>> references. these, and several other brands and models of voltage >>>> references, use the same or similar reference ICs as their basis. The >>>> reference ICs are a Zener/NPN transistor pair on a single >>>> substrate. Please view in a fixed-width font such >>>> as Courier. >>>> >>>> | >>>> | >>>> C | >>>> | >>>> | >>>> | >>>> |---- >>>> | B >>>> /| >>>> / | >>>> E | >>>> | >>>> +--------------- >>>> | >>>> /------/ >>>> / >>>> ------ >>>> | >>>> | >>>> >>>> Just thinking... would it be possible to make a reference with >>>> similar characteristics with discrete components (a low tempco >>>> Zener and a transistor)? They would likely have to be closely >>>> coupled thermally and >>>> maintained at a constant temperature within an oven or by a peltier >>>> device. >>>> >>>> What criteria would apply to the selection of the parts? >>>> >>>> Dave M >>>> >>> >>> There has been some of those references available second hand from >> ebay, mostly pulled, but some may be counterfeit, so look for sellers >> with pictures showing it as old. >> > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.