dead nicd charger

I'm going to risk the rath, but I just know someone on this list has delt with this. After replacing my Ryobi 14.4v nicd charger 2 times (yes 2), I discovered I have a dead battery and it's killing the charger(s). Apparently it can do this rather quickly, as I only left it on the charger for about an hour. (one web site says it only takes a matter of minutes - apparently the cheapo charger does not protect itself) So, ok. Since I have 2 dead ones I might as well try to fix it. It just as a simple circuit board with a rectifier, 4 devices, 3 leds and bunch of discretes. Q1 A1015 PNP transistor (2SA1015) Q2 2N3904 NPN transistor Q3 XL08 ST 40 .8A SCRS Q4 X0403DE ST SCR Anyone ever fix one? what fails? I'm going to guess the big to-225 style SCR failef, since I'll bet that modulates the current to the battery. -brad