Quoted from ChrisPINk25:... Here's the weird thing. The voltage at Pin 22 now reads 1.471v. What could cause that? I checked the battery pack multiple times and it was reading just below 4v.
Hi, looking at your battery pack, everything looks OK. The three cells delivers about 3 x 1.5 volts, so 4.5 volts. Then the protection diode (your pictures show it mounted in the right position) drop the voltage for about 0.6 volts, and you get at final a bit less than 4 volts. So, nothing wrong here.
On GTB SYSTEM 1, the memory power schematic is quite simple.
The diode CR26 prevents the current from going back in all the circuit. The R133 is use to charge the original NI-CAD battery.
VAB is the memory voltage, that power the 5101 RAM and the 4528 CMOS (Z2).
2017-11-29_07h48_20 (resized).jpg
There is no reason for the voltage to drop to 1.4 at pin 22 (VAB for 5101), unless:
- the diode CR26 is died, and don't stop the current
- you connect the battery pack at a wrong point
In both cases, the whole board is powered by battery, that is of course, insufficient. This can cause the voltage to dramatically drop.
Check the voltage on both pins of CR26 (this diode is located just above the NICAD battery): on cathode you should have about 4 volts, and nothing on the anode.