A follow up on this in case anyone else has a similar issue. The transistor (T6) in the cassette remote circuit went bad, keeping the motor relay's coil engaged all the time when memory power is on. Relay power comes from before the regulated section of the power supply and remains on even when the computer is off.
It wasn't until I ran it off an AC adapter and could hear the relay click when it was plugged in. The relay isn't very loud and I never noticed when installing batteries. On Wed, Apr 28, 2021, 04:27 Alex ... <abortretryf...@gmail.com> wrote: > I don't have any real measurements to back this up, but someone might find > this anecdote useful. > > I feel like my 102's AA battery life was much better after I cut out the > internal NiCd cell. This idea is supported by the fact that it again seems > to go through batteries faster since I replaced the backup battery with a > new one. > > Worth noting I run the machine on Eneloop NiMH cells, not alkalines. > > On Tue, Apr 27, 2021, 20:51 Peter Noeth <petern0...@gmail.com> wrote: > >> I know this has been discussed before, but I was doing some testing on my >> T102 regarding current drain to gauge external battery life. I made an >> external 4D cell alkaline pack I use when watching TV and playing with the >> computer a few years ago, and was thinking of upgrading the capacity. There >> is no convenient A.C. outlet near by to my viewing position, hence the >> battery pack. >> >> I measured this on a 32K Tandy 102 w/REX installed. >> >> - 0.4mA - Computer off, no peripherals connected >> - 66.5mA - Computer on running a BASIC program, no peripherals >> connected >> - 67.2mA - Computer running a BASIC program and printing to my >> DPU-414 thermal printer >> - 71.8mA - Computer running REXMGR, no peripherals connected >> - 114.7mA - Computer running a BASIC program, printer connected but >> powered OFF >> - 130mA - Computer running a BASIC program with Unitek Barcode Wand >> connected >> >> I am sure a M100 would give similar results, but maybe a little higher in >> some cases, due to the T102 being mostly surface mount components and the >> circuitry optimized somewhat over the M100 >> >> The surprise was the marked current increase with the printer connected, >> but powered OFF. There is obviously some sneak current paths if the printer >> is not ON. Likely in the printers Centronics interface chip. This is good >> to know if trying to maximize battery life. >> >> The current draw increase with the Unitek Barcode Wand connected was >> expected, due to the fact that it has a very bright red LED, that is on all >> the time. The RS Barcode wand likely draws less when its button is pressed >> to turn on the dim LED. I like the Unitek wand better, as it reads codes >> that are not black on a white background, like on food cans and potato chip >> bags. Radio Shack just private labeled the HP wand for the 41-C calculator, >> which was low power and expecting white paper barcode labels and program >> listings. >> >> Regards, >> >> Peter >> >
