Battlezone ARII 7905 help

Pepelepew

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I have been getting lines on my Battlezone and could never figure it out. I know the boards are good and the monitor. Rebuilt the ARII with Bob Roberts kit and still the same problem. Looked at it today and noticed the 7905 is shot again so I replaced it. Game looked good till the over voltage got to it and blew the 7905 again. -5v reads+11.93. What is causing the input voltage to blow the 7905? I looked but have not disassembled components to check, and I'm having a hard time starring at the manual photo, theres no schm and I dont know if that would help anyway. Ignorance is Bliss
Rick
 
You need a schematic. Email me at boucher at mnsi dot net and I'll email you a pdf.

There is most likely a bad diode in the bridge that rectifies 36VAC into DC. Replace CR5, CR6, CR7, CR8. It also wouldn't hurt to replace the caps C31 and C19. These parts are all there is with respect to sourcing -DC power to 7905.
 
Did both 7905's come from BR? A while back he apparently had a bad batch of regulators but I cant remember if it was 7905, 7805, or 7915. I blew a couple that had come from BR and then replaced from a different source and never had a problem again. Several other klov'ers reported the same thing.
Anyways its worth a try.
 
No,
The 1st was BR, the sencond was NTE 961. Both died the same horrible death. Must be tooooo much dc
 
No,
The 1st was BR, the sencond was NTE 961. Both died the same horrible death. Must be tooooo much dc

If the problem is a bad diode in the bridge circuit like I suggested previously, the problem isn't too much DC but instead too much reverse polarity caused by the AC getting to the 7905. Just a few volts the wrong way will pop it.

Also, since there is no protection diode across the 7905 (from input side to output side), if the input side cap is open (or lost microfarads due to age), then when you power down the machine the -5V stored inside the cap on the -5V side will backfeed through the chip to the input side and that will blow the chip. Change the caps!!! Or add a protection diode (ie 1N4007 or 1N4148 with cathode on the -5V side and anode on the input side).

If you need part numbers, check this list
http://www.biltronix.com/arcade_electcomp_01.html#arii0204

Another possible problem is that there's some sort of shorted load (ie shorted capacitor) on the -5V output. That's why I suggested changing the caps. There also might be a bad ram chip that is drawing too much -5V current and causing the 7905 to rapidly overheat. If the game runs fine until the 7905 dies, then it is likely not a ram chip but is very likely a bad cap.
 
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