XEGS: Where do I get these mobo switches?

[Marius]

Hi,

 

Today I received an Atari XEGS ... it's in a very good condition, except that unfortunately the reset switch on the mobo was defect. It wasn't there at all.

 

Is this a common available part?

 

I have access to farnell, and ebay ofcourse.

 

See picture. Thanks a lot.

 

Prowizard

 

[Marius]

Hmm... they seem to be not just switches. When I measure with my DMM the R when the key is not pressed = 1.7KOhm

When the key is pressed it falls down to 600 Ohm... and when I press harder it falls down to 400 Ohm.

 

What kind of switches are these?

[Rybags]

They should be fairly common microswitches that can still be had from electronics suppliers.

 

The Reset mechanism is different on XE vs XL - on XL you press RESET and it's instant and remains active until you release the key.

 

On XE, RESET does nothing until you release the key and it generates a momentary RESET signal.

I should think that the circuit to do that would explain the readings you get when measuring it.

[Marius]

Ok ... But a circuit can not give a resistance over A and B when A and B are short circuit with a switch.

 

So I need to know is there anything special to these switches? They only have two pins.

[Rybags]

Likely there's some oxidization on the contacts and pressing harder just makes the switch work a bit better.

[AtariLeaf]

I read the title thread as "Where do I get these "mofo" switches"

 

BTW, I thought that Best sold these switches?

Edited February 13, 2014 by AtariLeaf

[re-atari]

Hi,

 

Today I received an Atari XEGS ... it's in a very good condition, except that unfortunately the reset switch on the mobo was defect. It wasn't there at all.

 

Is this a common available part?

 

I have access to farnell, and ebay ofcourse.

 

See picture. Thanks a lot.

 

Prowizard

Easiest solution that comes to mind is to try attach some kind of microswitch to the keycap in the upper case shell. The plastic 'riser' is missing, so you'd have to bridge the space between the PCB and the keycap anyway. Check the switch pinout, and connect wiring accordingly. AFAIK they are just pushbutton switches that make a closed connection when depressed. The variation in readout you experienced may well just be the result of contact resistance between the solderpads and your multimeter probes.

 

re-atari

[russg]

Hi,

 

Today I received an Atari XEGS ... it's in a very good condition, except that unfortunately the reset switch on the mobo was defect. It wasn't there at all.

 

Is this a common available part?

 

I have access to farnell, and ebay ofcourse.

 

See picture. Thanks a lot.

 

Prowizard

 

Radio Shack, any electronics store. Farnell is a little hard to find the SPST pushbutton switch. My local electronics store is pretty easy to shop online. The problem is that nobody is going to sell

you a single switch you need for $.50 or $.25. Here's a sample page from my store. (You can buy a single switch if you have a brick and mortar store to shop in.)

It is a 'off-on' SPST pushbutton. Means off when not pushed, closed when pushed.

(SPST = single pole single throw)

 

 

http://www.electronicsurplus.com/Item/162914/OMRON%20-%20Switch_%20pushbutton_%20SPST%20NO_%20-%20B3F-1070/

Edited February 14, 2014 by russg

[Kyle22]

It is most likely a cheap carbonized rubber button type switch. That would explain the resistance. A "normal" switch should work fine.

[Marius]

It is most likely a cheap carbonized rubber button type switch. That would explain the resistance. A "normal" switch should work fine.

This is brilliant! It also explains why pressing harder gives a lower value. I also wondered why those keys also feel a bit mushy. Yes! That must be the reason.

 

So a regular 0 ohm 'short circuited' switch will do and won't harm anything?

[Kyle22]

yes

[dphirschler]

I am repairing one for my friend. At the moment, I have it working with some wires that I soldered in place. I just press them down to ground to trigger them. Lol