Apple II Plus No Video, No Beep, but Power Light On

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Joined: Feb 13 2018
Posts: 1

I recently bought a working Apple II Plus from eBay and it worked great. However, a few hours later I pulled the top off while it was on, and the video signal cut out. I turned it off and back on again and now only the power light comes on. No beep on boot or video output. Several Apple repair manuals I have found give a list of a few chips that may cause this exact issue. These are the 74LS00, 74LS174, 74S86, 74LS02, 74LS153, and 74LS195 chips at locations A2, B1, B2, B13, C1, and C2. There's a slight problem in that at positon B1 my board has a 74LS175 chip. The 174 is a hex d flip-flop while the 175 is a quad d flip-flop. I have been testing the chips to see which ones are bad, however, so far I have shown that the 74LS00, 74LS175, 74S86, and 74LS02 are fully functional. I tested the 74LS153, but the results were patchy. I have yet to test the 74LS195. One thing I did notice, the power supply is giving some strange readings on my multi-meter. There are slight variances in the voltage, around 0.1 V on the 5 V and -5 V lines and up to 0.5 V on the 12 V and -12 V lines. More importantly, the current on the different lines was vastly different than the ones listed on the power supply. All of the lines except for one had 0.1 A of current, while the 5 V had more than 10 A (It's supposed to have 2.5 A according to the sticker). Could the power supply be the root of my issue? Or is it more likely that the issue is in those last two chips? I think it may have been handled a bit roughly during shipping, the speaker was loose and the language card was also out of its socket. Any help is really appreciated! Thanks!