If that works, just leave the bad RAM slot empty, and go with "what works". Buy an 8gb DIMM and put it in "the BOTTOM slot" (with the back off) If taking out the upper RAM makes the computer "run as it should", then what I would do is: Try to boot and run that way a day or two. Remove the RAM DIMM "nearest to you" (topmost slot with back off).
If you're STILL getting the display problems Put the back on and see if that changes anything. Clean off the contacts, then reseat the RAM back into the DIMM slots. take off the back cover (you need a Phillips #00 driver for the screws, and pay attention to where "the long screws" go). Might be worth taking it in an having it replaced. Although this doesn't sound like a problem that would give you "the three beeps".ĭo you have a brick n mortar Apple Store anywhere close?Īpple -used to have- a free replacement program for the ribbon cable in the 2012 MBP's.
On some Mac models, you might hear one of these sequences of beeps at the beginning of the startup process, while the screen is still blank. The cable "wears" the internal connections go bad, or sometimes it even "shorts out" against the back cover. Certain conditions related to memory or firmware might be causing your Mac to beep once or more during startup. Also, the SATA ribbon cable that connects the internal hard drive to the motherboard (it's a "known weak" component on the 2012-design non-retina MBP's). RAM slot - intermittent contact from back of case "pressing on" the topmost RAM DIMM (that's why you see it act up when you set it on a surface) The basic circuit is also very forgiving on the power supply voltages (5-15V), a 9 volt battery will work well.If you get "3 beeps in a row" - that's an indication of "RAM troubles". If the battery is far away then you might want to put a filter cap on the power supply.
The capacitor on pin 5 isn't necessary, but will prevent glitches for more precision applications. 1uF cap for R and C will give you a minimum frequency of 70 hertz, which isn't quite sub audio but close. You could even experiment and eliminate the 100 uF capacitor on the 1st circuit, if the speaker can take the DC then it will work OK. 555 ICs are not meant for high power, but they are cheap and available almost anywhere parts are sold. Use the power supply for the 1st circuit to turn it on/off, the third schematic shows a way of digitally turning the oscillator on/off, as well as a major power boost if the first circuit is too quiet, while the second circuit shows a more conservitive way of boosting power (you will need a power transistor and a possibly a heatsink). The pots maximum value sets the low frequency, you should be able to adjust it to whatever note you want. If you still want to built the classic astable you pointed out let me know.
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