Reviving a Talyvel inclinometer

replying to greg, Bruce Allen wrote: The Talyvel 1 manual (page 12 of 20) says, "Two batteries are used in series, each giving a nominal 6.7 volts when new. A voltage regulating circuit in the meter permits satisfactory operation down to 4.5 volts each." I would advocate replacing these two SKB-830 batteries with four Lithium Ion 18650 rechargeable batteries (nominally 3.7-.4.2 volts each) plus two low-dropout 6V regulators.

replying to Bruce Allen, Bruce Allen wrote: For anyone who is wondering, the Talyvel 1 and 2 require a 9-13 VDC with no "center tap". The red wire is positive and the white wire is negative. The Talyvel MKIII amplifier board has an onboard voltage regulator, that consists of a PNP pass transistor and a 6.8V zener diode reference.

replying to Bruce Allen, Bruce Allen wrote: For anyone who is wondering, the Talyvel 1 and 2 require a 9-13 VDC with no "center tap". The red wire is positive and the white wire is negative. The Talyvel MKIII amplifier board has an onboard voltage regulator, that consists of a PNP pass transistor and a 6.8V zener diode reference.

Bruce here again. According to the Talyvel 1 manual, the original batteries were 6.7 volts each when new. Since the two batteries are in series, this gives a total voltage of 13.4 volts. According to the same manual, the minimum operating battery voltage is 4.5 volts per battery, giving a total voltage of 9 volts. (This makes sense: the internal voltage regulator produces 6.3 volts, and needs at least a couple of volts more than that to operate.

So to correct what I wrote a year ago, it is perfectly sufficient to use three 18650 Li-ion cells in series. This produces a maximum of 12.6 volts and a minimum of 10.8 volts. I have restored several Talyvel 1, and this works well in practice.