Regarding the 731B: The E505 is a 1ma current regulator. It is still available at a premium price but can be replaced by a Vishay J505. Slightly different package, TO92 vs TO18, but it does work. The J505 is available from multiple sources for about US$2 including several on the Bay. The U1 LM308 opamp can occasionally be destroyed if voltage is back-fed into the 10V output. Don't ask. Regarding the 750A batteries: I replaced mine with four ER14250/LS14250 1/2AA 3.6V 1200mAh lithium cells. Remove the original mercury battery holder and replace it with a dual AA cell holder. Use the kind that has the batteries side-by-side because you need to connect to the center tap between the cells. Wiring is pretty much identical to the way the mercury battery holder was wired. Install the lithium cells in a series string and you have +/-7.2V which is a bit higher than the +/- 6.75V of the mercury batteries but still works. The lithium cells have slightly more mAh capacity than the mercury cells and a much longer shelf life which works well for the 750A as the protection circuit draws very little current. Don't disable this protection circuit, it's too easy to fry the divider string if you're not paying attention. Thanks - Steve

On 11/22/2012 7:49 AM, Steve Smith wrote: > Regarding the 731B: > > The E505 is a 1ma current regulator. It is still available at a > premium price but can be replaced by a Vishay J505. Slightly different > package, TO92 vs TO18, but it does work. The J505 is available from > multiple sources for about US$2 including several on the Bay. > > The U1 LM308 opamp can occasionally be destroyed if voltage is > back-fed into the 10V output. Don't ask. > > Regarding the 750A batteries: > > I replaced mine with four ER14250/LS14250 1/2AA 3.6V 1200mAh lithium > cells. Remove the original mercury battery holder and replace it with > a dual AA cell holder. Use the kind that has the batteries > side-by-side because you need to connect to the center tap between the > cells. Wiring is pretty much identical to the way the mercury battery > holder was wired. Install the lithium cells in a series string and you > have +/-7.2V which is a bit higher than the +/- 6.75V of the mercury > batteries but still works. The lithium cells have slightly more mAh > capacity than the mercury cells and a much longer shelf life which > works well for the 750A as the protection circuit draws very little > current. Don't disable this protection circuit, it's too easy to fry > the divider string if you're not paying attention. > > Thanks - Steve > > > > > _______________________________________________ > 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. > You can always contact Fluke as they still stock a large selection of parts for their equipment. Prices aren't too bad either. I had a 6071a generator that I needed some special parts for and were able to get them from Fluke.