Well, I have this Roadblasters that has this funny issue. After being on about 30 minutes or so it has this vertical roll but I know it's not the monitor because the upper segment stays stationary. I looked this up and actually found a tech brief about it. The suggested fix was to replace the 7905 (-5 V regulator) and maybe Q6 (a common 3906 NPN trans)
I went ahead and replaced the regulator, two caps and a couple of related ICs just to update the whole circuit. I didn't replace the transistor because it tested good. I installed it and it still rolls after about 30 min. I swapped out the speech IC (TMS5220 also recommended) and there was no change. In the tech brief it says if the -5 is anything less than -5.00 then change the regulator but if the speech clock signal is less than +8 volts peak to peak then replace the TMS5220 @U13 (I could be wrong about the location, going of off of memory here) I haven't verified the clock voltage yet because I just haven't had the time to pull the scope off of my bench. I guess my real question is: Have any of you dealt with this specific issue before and what seemed to be the real cause. I suspect the ARIII to be noisy or failing but haven't checked that yet either. I also changed out big blue early on before I realized it had this issue. Anybody know?
I went ahead and replaced the regulator, two caps and a couple of related ICs just to update the whole circuit. I didn't replace the transistor because it tested good. I installed it and it still rolls after about 30 min. I swapped out the speech IC (TMS5220 also recommended) and there was no change. In the tech brief it says if the -5 is anything less than -5.00 then change the regulator but if the speech clock signal is less than +8 volts peak to peak then replace the TMS5220 @U13 (I could be wrong about the location, going of off of memory here) I haven't verified the clock voltage yet because I just haven't had the time to pull the scope off of my bench. I guess my real question is: Have any of you dealt with this specific issue before and what seemed to be the real cause. I suspect the ARIII to be noisy or failing but haven't checked that yet either. I also changed out big blue early on before I realized it had this issue. Anybody know?

