VERY IMPORTANT Works:I went Thrifting a few days ago... after wiping down with sanitizer and leaving in the mud room for a couple days quarantine, it was time for this VERY important project.
I shoved aside my relatively unimportant racing micro-quadcopter build, and got to work.
First things first... this thing has sirens and diesel horns, AND a really aggravating diesel engine sound whenever anything is running. But the little sound PCB-blob is pretty sensitive to drastic changes in loading; it sounds like staticky crap if you just dump a 100Ω resistor in series. A little trial & error with alligator leads came up with this solution that drops volume 60-80% while not making it sound like rocks in a camshaft all the time.
Next came time for a battery solution...
This thing came with
3 C-cells clusters of rust where 3 carbon-zinc C-cells used to be... I had no interest in going back to disposables, so cleaned the compartment as best I could without unwiring all the motors & stuff from the other side. Not very good, I know... but carbon-cell electrolyte does not clean up as well with Windex as alkaline-cell electrolyte does.
I got a couple of this cheap-ass "half load" (meaning that inside the cell is only half-filled or less with li-po jelly roll) batteries free with a flashlight; actual ~600mAH capacity is worthless for intended "purpose", and I can't think of anyplace else I'd ever use the damned thing.
Add a cheap (80c each in Qty 10) 18650 BMS-Charger module, and we have a power solution that's cheap as chips and easy as pie.
Charging and testing...
Everything lights up, the sounds all work at a very ignorable level, and the motorized ladder boom & wheels all work.
Time to give it to my daughter and collect my reward! There it is... that thousand watt smile! *sigh* An afternoon well-spent. mnem
Priorities.