Roadblasters vertical roll (not the monitor)

gregatron

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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?
 
No one? Somebody has to have seen this before.

Here's something that'll get your attention.
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Road blasters

Have you tried using a heat gun to isolate the area?
Or, after it starts to roll, try using freeze mist to find the area or the cool side of the heat gun to find out what area is causing the problem. Also try reseating the IC chips.

Besides the Big Blue caps,there is a rebuild cap/parts kit for the AR boards on bob roberts site.

RJ
 
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