A2000 A2630 hardware on/off switch

[SpeedGeek]

This isn't a very difficult hack or mod project. You need good soldering skills and the A2630 schematic. If you look at the schematic you will notice the PAL @ U305 has a signal called "68KMODE". This signal is asserted at a logical high state and negated at a logical low state. This signal is normally output from the Auto-Config register @ U303. This register normally comes out of RESET at a logical low state but can be changed to a logical high state by code in the A2630 boot ROMs.

So, if you disconnect the "68KMODE" signal from the Auto_Config register and connect it to a pull-up resistor and toggle switch to GND, you would then have a manual override circuit which bypasses the Auto-Config logic.   
   

[SpeedGeek]

The A2620 is functionally the same for mode selection as the A2630. The only thing you missed was that the pull-up resistor is connected to VCC. If it were connected to GND then it would be a pull-down resistor.

Regarding the value, Commodore liked to use 1K ohm resisters but I prefer to use a higher value 2.2K - 4.7K ohm.   
   

[SpeedGeek]

What you need is already sketched out in the schematic. Look at the RAMSIZ, NORAM and B2000 jumpers. The only difference is that you would substitute an SPST toggle switch in place of the jumper.

[SpeedGeek]

There are three 4.7K pull-up resistors in RP201. Pin 1 is the common pin which is connected to VCC (even though it's not shown in the schematic). When the jumpers are open the three signals are pulled to a logical high voltage and when the jumpers are closed they are pulled to a logical low voltage.

If you can't clearly envision this simple circuit, then you are not (yet) at a technical knowledge level needed to perform this modification. I would suggest that you solicit help from someone with the technical skills to do the mod for you.      

[SpeedGeek]

I could do the solder work, but I'm not 100% on the layout, and whether to cut a trace and solder there, or cut a pin and solder there, etc.

I keep looking for a switch-laden 3rd party A2000 accelerator coming thru eBay, but nothing. And I'm sure it would be quite pricey, looking at some of the things I do see coming through. (There's an 030 Derringer there now, but that seems not the ideal way to go on the A2000, direct to socket, etc.)

Are you aware of anyone in this forum community that would be willing and able to do this mod for me, for some level of compensation? Thanks.

I feel like I am kind of in a limbo with my A2000 having noted the issues that make me seek a switchable accelerator.

bp

Finding a trace to cut probably won't be easy if the A2620 has a 4 layer PCB like the A2630. The A2630 has most traces on the inner 2 layers and VCC and GND on the outer 2 layers.

So that leaves 2 options, cut the output pin on the LS174 chip or disconnect the input pin to the PAL. Since the PAL is socket mounted it's probably easier to remove a pin from the socket.

The rest is just a matter of wiring and soldering the components which should be done with a low temperature and grounded soldering iron. Mech is a long time Amiga.org member who could do the work for you. You should send him a PM and ask him about it.