Reset and NMI Switch for TurboTrans

Project: Reset and NMI switch for the TurboTrans.
Target : TurboTrans
Time   : 15 min.
Cost   : ~2 US$
Use    : - easily switch RAM banks and read disks into RAM.
         - reset hung up floppy without need to switch floppy on/off.

Summary

Push-button switch between

pin 6 (/RESET) and GND
pin 5 (/NMI) and GND

... and pull-up resistor to pin 5 (all pins refer to the soldering pads on the TT board in the 1541.

Details

Reading a disk into the TT's RAM and swapping RAM banks can be accomplished by issuing the appropriate command to the floppy. However, both functions can be executed by simply pressing a button. Alas, Roßmöller has saved the pull-up resistor for the NMI switch, so you have to add one yourself.

Ingredients

2 single-pole push-button switches (normally open)
4 x ~40cm of two-core cable
1 5.6kohm resistor (or 4.7kohm)

Instructions

Remove all cables, then open case.
Solder the wires to the two switches.
Solder one switch between pin 5 of the soldering pads depicted below and the pin above (GND), this will be the NMI switch.
```
 o-o-o-o-o-o-o-o  <- ground
 o o o o o o o o
 1 2 3 4 5 6 7 8
```
Solder the other switch between pin 6 and the pin above (GND), this will be the reset switch.
Below the 16 solder pads on the top you can see a large ground pad with a hole in it and three solder pads to the right. Solder the resistor between the top of the three pads (+5V) and pin 5 of the upper 16 pads (pin 5 means the LOWER pin of the two, otherwise you would shortcut +5V and ground - ouch!).
Test both switches. Pressing the NMI switch once will switch the RAM banks. When you press it once, wait for the floppy LED to light up, and then quickly press it again (with the LED still on), the TT will read the disk into the current RAM bank.
If it seems to work, close the case again.

Possible failures

Are you sure that the push-button switch is normally OPEN?

Updated: December 5th, 1997
Created: December 5th, 1997
Status : Verified on December 5th, 1997