Posted By
JamesC
on 2016-11-06
10:27:53
|  Re: My C16 +4 has died
Unfortunately, there are several possible points of failure for the symptoms you describe. 
1. If you are using a modern television or monitor, try attaching the Plus/4 to an older television (pre-digital era). Or if you use a converter between the Plus/4 and your television/monitor, feed another video source to it (such as a DVD player) to verify that the converter itself is not contributing to the problem.
2. The Plus/4 power supply could be delivering low voltage. The power indicator can light up, yet there not be enough power for the processor or video controller to initialize. If you have a multimeter, check for 5V DC between the bottom two pins of the power connector. You need a solid, unwavering 1 to 1.5 amps here. (The upper two pins deliver 9V AC, but for the symptoms you describe we can ignore this.)
3. If you have a multimeter, go through Troubleshooting 1 and 2 of this link: Plus/4 Service Manual and supplements
4. On startup, the processor must initialize itself, then initialize the video controller, and finally initialize BASIC. If these chips do not "see" their 5V, then the system will appear "dead". Inspect the motherboard for blown capacitors, burnt resistors, and cracked solder points.
4b. The processor (U2, marked 7501 or 8501) and video controller (U1 inside the metal cage, marked 7360 or 8360) are unique to the Plus/4 series (including the 16 and 116), so finding replacements of these chips could be difficult or expensive. It might be cheaper to replace the computer, and save your current one for repair parts.
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