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Macintosh Plus Chirping Noise


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Hi and welcome in thuis forum. Chirping sound seens to be a well known problem. I'm on my mobile now but on my computer is a PDF of a book called The Dead Mac Scrolls. I'm sure you can find the book somewhere on internet or maybe there is a fellow forum member who can look up what the problem could be.

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Hi Jack, welcome!

 

You can get the aforementioned book here: http://maccaps.com/MacCaps/Repair_books_files/The%20Dead%20Mac%20Scrolls.pdf

Check what the book tells you to check but don't screw around with the potentiometer labelled R56 (it will usually cause more problems...). BTW, the problem is with the analog board (the vertical one). 

 

Do you have the tools to take your Mac apart? You need a very long T15 screwdriver. 

 

If you have everything, I recommend that you don't take it apart right now. Even when the Mac is off, some components can still hold a charge (thousands of volts in some cases). Let it discharge itself for a couple of days (a week?) and you should be safe to proceed. Technically, you should discharge the CRT before working on the analog board, but if your mac was made in 1987 or up, it should discharge itself quicker. Check your serial number to known when it was made.

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Thanks for replying, I have discharged the mac and have it apart, I've checked the Dead Mac Scrolls it doesn't seem to have my problem the chirping noise sounds like its coming from the low voltage power supply. Ive checked the voltages and i can't seem to find anything abnormal except the chirping noise. Any suggestions?

 

I'll also post a video of the chirping noise

 

https://youtu.be/KXNf49hQGiY

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thats not chirping. 

 

That is known as "ticking" and its caused by the power supply unable to go into regulation. Either from too little or too heavy of a load. 

 

Chirping and Ticking are very different and have very different sounds. So lets hopefully clear that up. Chirping is usually a loud squeek/chirp sometimes it wails up, or wails down in frequency for a short second before re-cycling depending on the design of the power supply. This is caused by a VERY heavy load, or a short circuit on one of the secondaries. 

 

Ticking is different. its a light tick-tick-tick like a clock. Rarely is this caused by a short circuit unless it is a power supply of limited current capability. 

Edited by techknight
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  • 3 weeks later...

thats not chirping. 

 

That is known as "ticking" and its caused by the power supply unable to go into regulation. Either from too little or too heavy of a load. 

 

Chirping and Ticking are very different and have very different sounds. So lets hopefully clear that up. Chirping is usually a loud squeek/chirp sometimes it wails up, or wails down in frequency for a short second before re-cycling depending on the design of the power supply. This is caused by a VERY heavy load, or a short circuit on one of the secondaries. 

 

Ticking is different. its a light tick-tick-tick like a clock. Rarely is this caused by a short circuit unless it is a power supply of limited current capability. 

 

Yeah I know,  Apparently it sounds different in person  I guess the mic on the camera was not picking the noise up properly. Sorry about that

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  • 1 month later...

I've found a possible cause of the problem, The Dead Mac Scrolls has something about the power/video cable and to check the continuity of both sides of the blue wire (or Pin 6) and it did not have continuity. There also seems to be a resistor in between the two ends of the wire. is there anything special I should know about it?

 

Thanks, Jack

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