| Arcade Collecting > Restorations & repair |
| (another) Space Invaders |
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| RetroACTIVE:
That power supply uses the LM305 for its 5 volt regulator... probe that to see if its doing its job... I suspect it may not be :cheers: http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/LM305.pdf Man do I want to get back to my SI!!!! Life has taken over again :( |
| Spyridon:
--- Quote from: RetroACTIVE on February 03, 2011, 09:27:49 am ---That power supply uses the LM305 for its 5 volt regulator... probe that to see if its doing its job... I suspect it may not be --- End quote --- I'll check that out. Thanks for the link, that will help me figure out how to test it. I did replace the 2n3055 transistor but that didn't help. |
| Spyridon:
--- Quote from: RetroACTIVE on February 03, 2011, 09:27:49 am ---That power supply uses the LM305 for its 5 volt regulator... probe that to see if its doing its job... I suspect it may not be --- End quote --- Some progress, but not quite there yet. I checked the LM305 and it was taking in +12.92v unregulated and spitting out +5.82v. I replaced it and now it is much closer to +5v. However, now I'm down to +4.78v at the test point and the pot still doesn't change the value. I need to look at the schematic and see what is between the LM305 and the test point. At 6.2v, I was getting garbage on the screen, at 4.8v, I don't get anything on the screen. Probably need to get it up around 5v to get any output. |
| Spyridon:
An update on this. With the PCB disconnected, I am reading 4.94v at the +5v test point on the power supply. Adjusting the pot does not change the voltage. Hooking up the PCB, the +5v drops to 0.651v. The -5v and +12v are fine. Something on the PCB is sucking the power down. |
| Spyridon:
I picked up a replacement backdrop Also, acquired a nonworking PCB and a working Power Supply to help troubleshoot the issues I'm having. |
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