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AT style reset switch

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First post, by pan069

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Hi all,

So, I have this socket 7 motherboard which is AT form factor but it also has a ATX power connector. Typical late 90's cross-over board I guess. I usually use ATX power supplies with an ATX -> AT converter for AT boards.

Since my case is AT and the board is AT but with ATX power it makes sense to go for ATX power instead of AT. However, the case is designed for an AT power switch (i.e. the one that's on typical AT PSU's) and this switch doesn't work on the PWR pins for the board. I.e. the AT power switch stays pressed after pushing it. I'm currently using a new (smaller) style reset switch to turn on/off the machine for testing but I'd like to use the actual power button on the case.

So, I'm looking for an AT style power switch (as in the image) that acts like a reset (i.e. comes back up after pressing it).

I have been unable to find them on eBay... 🙁

xzFQfBx.jpg

Reply 1 of 6, by SirNickity

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There's a guide pin in the top of that kind of switch that you can remove. IIRC, the front panel comes off by slightly bending two little legs. The whole plunger mechanism falls out then. There's a pin that hangs down from the top of the shell and follows a track inside the plunger. This is what locks the plunger in until you press it again to release it. Remove that pin and it becomes a momentary switch.

This is exactly what I just did for an AT case with an ATX PSU-compatible Pentium AT board.

Reply 2 of 6, by Ozzuneoj

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What you're looking for would be considered a momentary switch.

Momentary = the circuit is only connected when the switch is pressed or held, then it is disconnected when no longer pressed
Toggle = the circuit stays connected when pressed until it is pressed again

... There's probably a much better way to describe this.

Now for some blitting from the back buffer.

Reply 3 of 6, by feipoa

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SirNickity wrote:

There's a guide pin in the top of that kind of switch that you can remove. IIRC, the front panel comes off by slightly bending two little legs. The whole plunger mechanism falls out then. There's a pin that hangs down from the top of the shell and follows a track inside the plunger. This is what locks the plunger in until you press it again to release it. Remove that pin and it becomes a momentary switch.

This is exactly what I just did for an AT case with an ATX PSU-compatible Pentium AT board.

Interesting. I've never tried this before. Do all AT power switches have this capability?

There may also be a circuit component approach to turning a latching switch into a momentary one. I've done it the other way around before, that is, turning a momentary switch into a latching one with discrete components: Re: Cyrix MII-433GP Build

Plan your life wisely, you'll be dead before you know it.

Reply 5 of 6, by pan069

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Thanks @PARKE, just what the doctor ordered!

Reply 6 of 6, by SirNickity

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feipoa wrote:

Interesting. I've never tried this before. Do all AT power switches have this capability?

In some form, yes. It takes some mechanical element to create the latching action, otherwise push-button switches are all momentary. The inclusion of that element is the only difference. They may not all come apart the same way, and I'm sure some don't go back together again, but the small sample size I've evaluated all did.

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