Well. since the forum wants to talk about Runtz, I'll bring this up. Some swear by the Runtz and some don't. Some get upset if you post negative against it. HandyAndy had two Runtz (absolutely not a clone) to fail. He was kind enough to send me one so I could investigate. In this order left to right in the picture. Capacitor, Diode, 3-pin Regulator and Capacitor. The design of the circuit is basic, not copyrighted and is used as an example in one of the manufacturer's spec sheets. The regulator chip had failed. The other components were good.
The 3-pin regulator is a Fairchild KA808R in a D-Pak configuration. All of the components are surface mount devices (basically, no leads). There is no heat sink for heat dissipation of the regulator chip. The circuit board had no evidence of burning or a burning smell of a component that had failed. Specs says the KA808R output is good for up to 1 amp at less than 15 watts. The circuit board was enclosed in a heat shrink tube (not watertight).
Four things that bugged me. One is, no heat sink (it can get hot inside an AD cab). Two, the Runtz is mounted on a threaded stud of the cluster gauge assembly. What would happen if the cowl vent was opened and you happened to come up on a rain storm? Would it fail if it got a little wet? Three, is 1 amp - 15 watts enough? Testing is required. And finally four, why use a 8 volt regulator when the system is 6 volts? The voltage drop across a diode is typically 0.6 volts.
Let the cat fight begin.
Last edited by buoymaker; 07/15/20213:06 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
