Each of two APS model amplifiers that mounted directly to a 5-inch and 6×9-inch speaker frame. Both used a full bridge chip amplifier that ran directly off 14.4VDC vehicle power bus.
Two memorable issues with this product both involved mystery field failures of the product. In one case, it turned out that production, in order to speed up the build, started using a mallet to install the clip versus pressing it on by hand. This introduced micro-cracks in the soldered pins that, with repeated thermal stress, would fail over time.
The second issue was more insidious. A thermal insulator was replaced with paste to reduce cost; electrical isolation was not required. Soon after, some of the amps would randomly cut out. The IC was better coupled to the heatsink and was running cooler so one would expect no change if not an improvement in performance. It was ultimately discovered that the chip’s internal current limit had an undocumented dependency on its internal temperature. By running the chip cooler, it significantly lowered its (nonadjustable) current limit. The only viable solution was to put the thermal insulator back in and allow the chip to run within a prescribed temperature range.
