Joe Perez

iTrader: (8)

chiefmg

iTrader: (5)

92dx

iTrader: (2)

...sweat this on right quick

Joe Perez

iTrader: (8)

Holy cats. That actually is an official product image...



This is a filthy 20 year old power antenna gearbox. It's been making janky noises for a while, and only raising the mast about halfway. The cable finally snapped last week, with the majority of it remaining inside the box. So as I had to open it anyway, might as well do it up right.




It was a relief to find that none of the plastic components were cracked or chipped. There were some indications of wear on the teeth of the larger gears, but nothing significant.

And it was a surprise to see a Johnson brand motor in there. So far as I can tell, this is the original antenna gearbox for the car, made in Japan, with... US-sourced components? There's something you're not likely to encounter today...


I was also surprised by the complexity of the circuit board inside. I'd honestly been expecting a relay, a couple of microswitches, and maybe a self-resetting thermal fuse. But no, even in 1998, Mazda was finding excuses to hide semiconductors in the trunk.



I can't quite ID the make on the electrolytic capacitors, but they all appeared in perfect shape. No bulging, no leaking. At least Mazda (or their supplier of power antenna gearboxes) specified quality components.

The little BA10393 is a dual comparator. Could it be doing the current-sensing, along with that chonky 0.1Ω resistor right beside the motor wires, to figure out when the motor has reached the limits of travel and come to a stop?

74HC04AP is an ordinary hex inverter, perhaps being used as a set / reset.




TA8051P, now that's an interesting one. Bidirectional DC motor driver with overcurrent protection and brake function. Ok, now the use of semis makes sense. I can also see from the datasheet that the BA10393 is actually part of the TA8051P's signal path (it's in the example application circuit), though I haven't quite worked out why that functionality wasn't integrated into the main unit. There's something I'm missing with regard to the ~ST pin, will need to trace out the schematic for the board if I plan to understand that.

But that's not something I need to do.





Here's all of the parts laid out after their thorough cleaning, as though this were the prologue to a Wes Anderson film.



You can hear the light, plucky orchestral tune which is playing right now in your mind. It's probably something like this:




And, while listening to that, you can visualize me picking up each piece one by one, caringly ensconcing it in white lithium grease, and then setting it into position within the housing with robot-like cadence.


I failed to take a photo after re-assembling everything, largely because my hands were completely covered in white lithium grease. So, imagine three estranged siblings finally gathering around a fully assembled power antenna gearbox, with pained and slightly tearful expressions on their faces, shot on Kodak 200T / 5213 color negative film.

One of them picks up the gearbox, and a drop of grease falls from it, onto the cover of the diary which their father kept during his travels throughout southern Asia and the Pacific Islands in the 1960s, an artifact whose possession had previously been the catalyst of much jealousy between them.

But it's ok. The look in their eyes reveals that they have made peace, not only with their father's complex and controversial legacy, but also with themselves.