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hfrazier

Mac SE Monitor On/Off Switch

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Hi Everyone,

 

I would like to present my SE/30 monitor on/off switch. It's only a matter of removing two jumper wires on the analog board - W4 and W5 - and switching each of them on either pole of a DPST switch. (With optional LED, DigiKey P/N CKN2068-ND). Full instructions and more photos here in the album: https://imgur.com/gallery/m4IMHGU

 

 

QVWQspt.jpg

S44aiXn.jpg

Edited by hfrazier

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Nice job with that! Two devils advocate questions:

 

-Why do that when you can just turn the brightness down?

 

-Does that involve making a hole in an otherwise pristine case?

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11 minutes ago, LaPorta said:

Nice job with that! Two devils advocate questions:

 

-Why do that when you can just turn the brightness down?

 

-Does that involve making a hole in an otherwise pristine case?

Good questions!

 

Yes, you  will have to cut the case and some of the inner metal chassis. ...but the SE/30's are so awesomely hackable, why not? If you wish to run it as a server, the switch is fairly inconspicuous.

 

As for the reasoning... (besides bringing power consumption down to 34W from 47W)

When you turn down the brightness, all you do is save the screen from burn-in. The filament of the CRT is still powered and thus slowly burning up, and the flyback and horizontal/vertical deflectors are still running, consuming power (and shortening their lifespan.) This switch effectively cuts power to U1 which buffers the video signal going in to the driver circuitry and also cuts power to the CRT filament. The red circles are where the jumper wires are and the green circle is all of U1:

AB_mod.png

Edited by hfrazier

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Wouldnt it have just been easier/safer to put a switch in the sweep supply at pin10 on P3?

 

You will blow out that 74LS IC eventually doing it the way you are doing it. 

 

At minimum you need a Zener diode, a resistor, and capacitor filter network now at the IC. Just C23 alone isnt good enough anymore now that you have wires running half way to China and back, along with EMI generated by the switch, which is now closely coupled with the 12V line. All kinds of bad here.

 

But hey, at least you tried. :-)

Edited by techknight

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23 hours ago, techknight said:

Wouldnt it have just been easier/safer to put a switch in the sweep supply at pin10 on P3?

I tried that first, actually. Switching it back on made the logic board brownout and reset.

 

Quote

You will blow out that 74LS IC eventually doing it the way you are doing it. 

You are probably right, let's add those. Can you show me where to make those mods and I will add it to my original post so we can make the mod better?

Side note- I thought about using a piece of hollowed coax cable.. but thought that the twisted pair would be good enough for EMI.

Edited by hfrazier

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you just need to tack a couple capacitors. 0.1uf ceramic/film, and 1uf electrolytic. across the VCC/GND lines directly at the chip. Also, a 5.6V Zener diode with the stripe side of the diode body soldered on the VCC pin, and other lead to ground. 

 

Then, put a 10 ohm resistor between the wire coming in from the switch, and the chip's VCC where all the above parts are attached. this will serve as a dump resistor if something were to overvolt or short causing the zener diode to clamp. You could go with the metal film non flammable type here. Maybe fusible type so it pops open if failure. 

Edited by techknight

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