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Thread: Adding reset button to Amiga500?

  1. #1
    Brostenen's Avatar
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    Default Adding reset button to Amiga500?

    Hi all.
    Let me start my question, by saying that I am noob in reading schematics. Yet I have a tiny question on if I am reading the schematics correctly.

    I have this project, in were it would be so awesomme, if I was able to add a reset button to an Amiga500 board. Now, I thought that it was not possible, and that the Amiga 500 was only able to do hardware reset by doing it on the keyboard. Yet now I am really not sure if that is an urban myth or something.

    Well...
    I was looking in my 500 manual for a different reason, and I thought that it would be fun, just to look at the schematics in the back of the book. And on the first page, there is a mention of JP1, being the jumper for system reset vs keyboard reset. Then I looked at the 7th page of the schematics, in were the JP1 is found. It was marked as going to "_kbreset" and finally on the 6th page, the "_kbreset" is actually Pin6 on the connector for the keyboard.

    Well...
    That was a bit interresting I thought, and I found a picture of an Rev6a board that I have, and found the actual JP1 right below the transistor a bit to the right from were RESET is on the silk screen. And sure enough, the jumper is bridged by a solder blob.

    Now. If I remove the solder blob, and solder in a couple of jumper pins. Would this be possible to insert a switch from a PC-Case and if the switch is a momentary off switch, then I would actually be able to use both the switch and the keyboard. Are my reading of the schematics correct?

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    Aeberbach's Avatar
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    I have not looked at the sch or an A500 - but if it is currently bridged by solder then it may be that reset is caused by causing that bridge to be open circuit, normally it is unused with only keyboard reset being possible. So if you got a normally closed (NC) momentary switch that might work. (A PC case switch would not asthey are normally open, NO.) Until you press the button the switch is closed as the solder is closed now, when you press it is open. But wait on more advice before you buy one...
    Last edited by Aeberbach; 30th September 2019 at 01:56.

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    Brostenen's Avatar
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    Quote Originally Posted by Aeberbach View Post
    I have not looked at the sch or an A500 - but if it is currently bridged by solder then it may be that reset is caused by causing that bridge to be open circuit, normally it is unused with only keyboard reset being possible. So if you got a normally closed (NC) momentary switch that might work. (A PC case switch would not asthey are normally open, NO.) Until you press the button the switch is closed as the solder is closed now, when you press it is open. But wait on more advice before you buy one...
    Yup.... Normally people say that the 500 is only capeable of resetting by keyboard. I have only seen one single post, that I found through google search, in were someone claimed to have had this done. Yet the user was a bit rusty and the post seemed like he or she was not even sure if it was an Amiga500. That is if you read between the lines. Yet for what I can read, and thinking logically, then removing the solder blob on JP1, would kick the machine into permanent reset state. The line "system reset vs keyboard reset" on the first page, seems like it is possible to do this.

    Regarding the switch, then I am not going to use the one on the front of the case. It is one of them tiny ones, that require one to use a pencil og a pin of some sort. What I am going to do, is to mount one on the back of the case. That is, if this is possible to do.
    Last edited by Brostenen; 30th September 2019 at 02:07.

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    Vampire600's Avatar
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    You can also use Gary for kbreset https://www.amigaworld.de/workshops/reset-am-amiga/

  5. #5
    LONG LIVE RETROPIE! levo-ace's Avatar
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    Looking at the schematics the _KBRESET is tied high via a 10k resistor so all you need to do is wire one side of the switch ( momentary normally open ) to the blob ( jp1 ) and the other side to ground! and voila a reset switch and still with keyboard reset capability!!
    wiring across jp1 would only give control of the ability to do a keyboard reset. and , looking at the schematic , would inhibit power on reset.
    Last edited by levo-ace; 2nd October 2019 at 22:19. Reason: added extra info.
    Amiga cdtv , cd32 , 500 , 500+ , 600 , 1200 , 2000 lots of scsi drives tape streamers cd dvd jazz zip mo.
    too many others brands to list and Raspberry Pi , Arduino.

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